BacT/ALERT VIRTUO Microbial Detection System, BacT/ALERT VIRTUO, VIRTUO
Device Facts
| Record ID | K161816 |
|---|---|
| Device Name | BacT/ALERT VIRTUO Microbial Detection System, BacT/ALERT VIRTUO, VIRTUO |
| Applicant | bioMerieux, Inc. |
| Product Code | MDB · Microbiology |
| Decision Date | Mar 28, 2017 |
| Decision | SESE |
| Submission Type | Traditional |
| Regulation | 21 CFR 866.2560 |
| Device Class | Class 1 |
| Attributes | Real-World Evidence |
Real-World Evidence
| Submission | Device | Sponsor | RWD Sources | RWE Use Summary | Key Tags |
|---|---|---|---|---|---|
| K161816 · Mar 28, 2017 | BacT/ALERT VIRTUO Microbial Detection System, BacT/ALERT VIRTUO, VIRTUO | bioMerieux, Inc. | Clinical study of patient blood and sterile body fluid (SBF) specimens | The clinical study compared the performance of the VIRTUO system to the predicate BacT/ALERT 3D system using matched pairs of clinical specimens (blood and SBF) to demonstrate substantial equivalence. | Clinical performance; Method comparison; Blood culture; Sterile body fluid |
Clinical Evidence
| Study Design | Population | Comparator | Key Endpoints |
|---|---|---|---|
| Clinical Study to Evaluate Blood Cultures on VIRTUO and BTA 3D; Multi-center clinical study comparing matched pairs of clinical specimens | Adult and pediatric patients suspected of blood stream bacterial/yeast infections; Sample Size: Multiple cohorts (e.g., 1441 FA Plus bottle pairs, 1181 FN Plus bottle pairs, 202 PF Plus bottle pairs, 1046 SA bottle pairs, 1061 SN bottle pairs); Number of Sites: Multi-center | BacT/ALERT 3D Microbial Detection System | System agreement with positive clinical determination (true positive rate), false positive rate, false negative rate |
| Clinical Study to Evaluate Sterile Body Fluid Cultures (SBF) on VIRTUO and BTA 3D; Multi-center clinical study comparing matched pairs of clinical specimens | Adult patients suspected of infections; Sample Size: Multiple cohorts (e.g., 362 FA Plus bottle pairs, 419 FN Plus bottle pairs, 75 SA bottle pairs, 75 SN bottle pairs); Number of Sites: Multi-center | BacT/ALERT 3D Microbial Detection System | System agreement with positive clinical determination (true positive rate), false positive rate, false negative rate |
Indications for Use
BacT/ALERT® VIRTUO™ Microbial Detection System is an automated microbial test system capable of incubating, agitating, and continuously monitoring for the detection of aerobic, facultative, and anaerobic microorganism growth from blood and other normally sterile body fluids.
Device Story
BacT/ALERT VIRTUO is an automated blood culture system for clinical laboratories. It incubates, agitates, and monitors culture bottles (SA, SN, FA Plus, FN Plus, PF Plus) for microbial growth. The system uses a robotic arm for automated loading/unloading of bottles from a conveyor. Operation involves colorimetric sensing: CO2 production from microbial metabolism changes a gas-permeable sensor from blue-green to yellow; this increases light reflectance, which is monitored by an LED/photodiode optical system. Reflectance data is processed by proprietary firmware/software algorithms to detect growth. The system features a tactile graphical interface and internal network access. By automating bottle handling and continuous monitoring, it provides rapid detection of microorganisms, aiding clinicians in diagnosing bloodstream infections and guiding antimicrobial therapy.
Clinical Evidence
Multi-center clinical study compared VIRTUO and BTA 3D using matched bottle pairs (FA Plus, FN Plus, PF Plus, SA, SN) inoculated with blood or sterile body fluids. Primary endpoint was system agreement for positive clinical determination. Results showed equivalent performance across all bottle types. For blood cultures, VIRTUO demonstrated high sensitivity and specificity comparable to the predicate. False negative rates were low (0.16% to 1.01%). Analytical studies (precision, LoD, delayed entry, interference) further supported equivalence.
Technological Characteristics
Colorimetric sensor-based detection; reflected light monitoring of CO2 production. Modular instrument (A Unit, B Units) with robotic loading/unloading. Capacity: 432 cells per unit. Connectivity: Networked or standalone. Software: Embedded firmware/software with growth detection algorithms. Sterilization: Not applicable (instrument). Materials: Standard laboratory instrument components.
Indications for Use
Indicated for use with BacT/ALERT FA Plus, FN Plus, PF Plus, SA, and SN bottles for the detection of aerobic, facultative, and anaerobic microorganism growth from human blood and sterile body fluid cultures. Prescription use only.
Regulatory Classification
Identification
A microbial growth monitor is a device intended for medical purposes that measures the concentration of bacteria suspended in a liquid medium by measuring changes in light scattering properties, optical density, electrical impedance, or by making direct bacterial counts. The device aids in the diagnosis of disease caused by pathogenic microorganisms.
Predicate Devices
- BacT/ALERT® 3D Microbial Detection System (K903505/A2)
Submission Summary (Full Text)
{0}
# **510(k) SUBSTANTIAL EQUIVALENCE DETERMINATION
DECISION SUMMARY
ASSAY AND INSTRUMENT COMBINATION TEMPLATE**
# **A. 510(k) Number:**
K161816
# **B. Purpose for Submission:**
To obtain a substantially equivalent determination for a premarket notification for the BacT/ALERT VIRTUO Microbial Detection System (VIRTUO) for use with BacT/ALERT SA, SN, and PF Plus blood culture bottles inoculated with human blood specimens and for FA Plus and FN Plus blood culture bottles inoculated with human blood or sterile body fluid (SBF) cultures.
# **C. Measurand:**
Growth of aerobic, anaerobic and facultative microorganisms in BacT/ALERT FA Plus, FN Plus, PF Plus, SA, SN bottles from blood and/or sterile body fluid cultures.
# **D. Type of Test:**
BacT/ALERT VIRTUO is a continuous monitoring blood culture system to be used in conjunction with BacT/ALERT SA, SN, FA Plus, FN Plus and PF Plus blood culture bottles. These blood culture bottles contain liquid culture media for recovery of microorganisms from blood and/or sterile body fluids. Colorimetric sensors are embedded in each bottle and reflected light is used to monitor the presence and production of carbon dioxide generated by the growing organism.
# **E. Applicant:**
bioMérieux, Inc.
# **F. Proprietary and Established Names:**
BacT/ALERT® VIRTUO™ Microbial Detection System (VIRTUO)
BacT/ALERT® FA Plus Culture Bottle (FA Plus)
BacT/ALERT® FN Plus Culture Bottle (FN Plus)
BacT/ALERT® PF Plus Culture Bottle (PF Plus)
BacT/ALERT® SA Culture Bottle (SA)
BacT/ALERT® SN Culture Bottle (SN)
1
{1}
# **G. Regulatory Information:**
# 1. Regulation section:
21 CFR 866.2560, Microbial Growth Monitor
# 2. Classification:
Class I
# 3. Product code:
MDB
# 4. Panel:
83, Microbiology
# **H. Intended Use:**
# 1. Intended use(s):
BacT/ALERT® VIRTUO™ Microbial Detection System is an automated microbial test system capable of incubating, agitating, and continuously monitoring for the detection of aerobic, facultative, and anaerobic microorganism growth from blood and other normally sterile body fluids.
# 2. Indication(s) for use:
Same as the intended use
# 3. Special conditions for use statement(s):
Prescription Use Only
# 4. Special instrument requirements:
BacT/ALERT VIRTUO Microbial Detection System is indicated for use only with BacT/ALERT FA Plus, FN Plus, PF Plus, SA, and SN bottles.
# **I. Device Description:**
The VIRTUO system is the next generation of the bioMérieux BacT/ALERT Microbial Detection System. This blood culture instrument consists of an incubator, agitation
2
{2}
mechanism, robotic apparatus for automated loading and unloading of bottles and a tactile graphical interface. VIRTUO is used in conjunction with existing, commercialized BacT/ALERT reagent bottles for clinical use (BacT/ALERT SA, SN, FA Plus, FN Plus and PF Plus culture bottles). The VIRTUO system utilizes a colorimetric sensor and reflected light to monitor the presence and production of carbon dioxide (CO₂) dissolved in the culture medium. If microorganisms are present in the inoculated sample, carbon dioxide is produced as the organisms metabolize the substrates in the culture medium. When growth of the microorganisms produces CO₂, the color of the gas-permeable sensor installed in the bottom of each culture bottle changes from blue-green to yellow. The color change results in an increase of reflectance units monitored by the system. The VIRTUO optically monitors the reflectance of each bottle over time and will store and interpret readings against algorithms, which are embedded in the firmware and/or software.
The VIRTUO system is modular with an A Unit, which is the main unit of the instrument and B Units, which are adjacent to the A Unit and are identical except for the following features:
- A Units can be used alone and have large and small LCD/Touchscreens mounted on the front chassis. A Units can also support an external PC.
- B Units can only be used in conjunction with an A unit and have only a small touchscreen display. The bottle loading area of the B Unit includes a removable plastic housing.
In the Standalone Configuration a customer can have a single (A Unit) instrument or can have a bank of instruments (A Unit + up to three B Units) that can stand alone or be connected to a customer network. Each instrument cabinet contains 16 racks with space for 27 bottles per rack for bottle monitoring. Four cells are dedicated for calibration standards. An instrument (either an A Unit or B Unit) has a total capacity of 432 cells.
### J. Substantial Equivalence Information:
1. Predicate device name(s):
BacT/ALERT 3D Microbial Detection System
2. Predicate 510(k) number(s):
K903505
3. Comparison with predicate:
3
{3}
| Similarities | | |
| --- | --- | --- |
| Item | Device K161816 | Predicate K903505 |
| Intended Use | BacT/ALERT VIRTUO Microbial Detection System is an automated microbial test system capable of incubating, agitating, and continuously monitoring for the detection of aerobic, facultative, and anaerobic microorganism growth from blood and other normally sterile body fluids | The BacT/ALERT 3D Microbial Detection System is a totally automated test system capable of incubating, agitating, and continuously monitoring aerobic and anaerobic media inoculated with patient specimens suspected of having bacteremia, fungemia, and/or mycobacteremia |
| Specimen types | Human blood and normally sterile body fluids | Same |
| Bottle Types | For use with FA Plus, FN Plus, PF Plus, SA, and SN culture bottles | For use with FA Plus, FN Plus, PF Plus, SA, SN, MP, FA, and FN culture bottles |
| Detection Technology | Reflection change of colorimetric sensor over time to measure metabolic reactants produced from organism growth | Same |
| Data Analysis | Data Analysis is performed by instrument embedded software | Same |
4
{4}
| Differences | | |
| --- | --- | --- |
| Item | Device K161816 | Predicate K903505 |
| Instrument | BacT/ALERT VIRTUO Microbial Detection System | BacT/ALERT 3D Microbial Detection System |
| Indicated Bottle Types | FA Plus, FN Plus, PF Plus, SA, and SN culture bottles | Same, in addition to FA, FN and MP culture bottles |
| Capacity | 108-6912 bottles | 240-1440 bottles |
| Bottle Loading | Automated loading of bottles placed on conveyor (up to 40 at a time) with bottle label scanning, measuring of sample volume & loading via robotic arm into open incubator cell with appropriate agitation. Customer can manually load bottles if automation features are not | Customer scans bottle labels and loads the bottle into a bottle cell of an open drawer, one bottle at a time |
| Bottle Unloading | Bottles unloaded automatically via a robotic arm | Bottles manually unloaded one at a time |
### K. Standard/Guidance Document Referenced (if applicable):
1. Clinical and Laboratory Standards Institute(CLSI): Principles and procedures for blood cultures M47-A, Vol. 27, No 17
2. ISO 15223-1:2012 Medical Devices - Symbols to be Used with Medical Device Labels, Labeling and Information to be Supplied
3. EN 61010-1: 2010 Safety Requirements for Electrical Equipment for Measurement, Control and Laboratory Use Part 1: General Requirements Part 1: General Requirements
4. IEC 62366:2007 Medical Devices - Application of Usability Engineering to Medical Devices
### L. Test Principle:
The VIRTUO system utilizes a colorimetric sensor and reflected light to monitor the presence and production of carbon dioxide (CO₂) dissolved in the culture medium. If
5
{5}
microorganisms are present in the inoculated sample, carbon dioxide is produced as the organisms metabolize the substrates in the culture medium. When growth of the microorganisms produces CO₂, the color of the gas-permeable sensor installed in the bottom of each culture bottle changes from blue-green to yellow. The color change results in an increase of reflectance units monitored by the system. VIRTUO optically monitors the reflectance of each bottle over time and will store and interpret readings against algorithms, which are embedded in the firmware and/or software.
# M. Performance Characteristics:
# 1. Analytical performance:
Note: FA Plus and PF Plus culture bottles are identical except for bottle labeling and recommended specimen volume. In addition, the detection algorithms for VIRTUO and BTA 3D are the same for both bottle types. Therefore PF Plus bottles were not evaluated in analytical studies and results from FA Plus bottles were used to support analytical performance of PF plus bottles on VIRTUO.
# a. Precision/Reproducibility
# Reproducibility Study
The reproducibility of the VIRTUO System was evaluated using six representative organisms of the most common pathogens associated with blood stream infections. The study was performed at three sites (1 internal and 2 external). One or more operators at each site performed two runs per day with two lots of FA Plus culture bottles over five days of testing for a total of 90 culture bottles tested at each clinical site for a total of 270 seeded bottles. Additionally, 48 negative control bottles containing only blood were evaluated. For calculation of percent recovery, positive results reflect a positive flag by the instrument and Gram stain/subculture consistent with the seeded organism.
The organisms evaluated and concentrations used for bottle inoculation are shown in Table 1.
Table 1: Reproducibility Study Organisms
| Microorganism | Inoculum, Concentration | Microorganism | Inoculum Concentration |
| --- | --- | --- | --- |
| Staphylococcus aureus | ~30 CFU/bottle | Pseudomonas aeruginosa | ~30 CFU/bottle |
| Candida albicans | ~100 CFU/bottle | Haemophilus influenzae | ~100 CFU/bottle |
| Escherichia coli | ~30 CFU/bottle | Streptococcus pneumoniae | ~100 CFU/bottle |
The reproducibility study demonstrated that the VIRTUO instrument generated 100% positive results for all FA Plus bottles evaluated. In addition, 100% of negative control bottles were reported as negative by the instrument. Study results are shown in Table
6
{6}
2.
Table 2: Reproducibility Study Results
| Organism | % Recovery (# detected/# tested), [95% CI] | | | | Time to Detection (hours) | |
| --- | --- | --- | --- | --- | --- | --- |
| | Site 1 | Site2 | Site3 | Overall | Mean | Range |
| Staphylococcus aureus | 100.0% (15/15) | 100.0% (15/15) | 100.0% (15/15) | 100.0% (45/45) [92.1·100.0] | 12.43 | 11.93 - 13.37 |
| Candida albicans | 100.0% (15/15) | 100.0% (15/15) | 100.0% (15/15) | 100.0% (45/45) [92.1·100.0] | 27.64 | 20.20- 38.83 |
| E. coli | 100.0% (15/15) | 100.0% (15/15) | 100.0% (15/15) | 100.0% (45/45) [92.1·100.0] | 8.62 | 8.10-9.25 |
| Pseudomonas aeruginosa | 100.0% (15/15) | 100.0% (15/15) | 100.0% (15/15) | 100.0% (45/45) [92.1·100.0] | 14.06 | 13.27-15.65 |
| Haemophilus influenzae | 100.0% (15/15) | 100.0% (15/15) | 100.0% (15/15) | 100.0% (45/45) [92.1·100.0] | 14.02 | 11.64-17.31 |
| S. pneumoniae | 100.0% (15/15) | 100.0% (15/15) | 100.0% (15/15) | 100.0% (45/45) [92.1·100.0] | 12.07 | 10.86-13.59 |
| Negative Control | 0% (0/15) | 0% (0/15) | 0% (0/15) | 0% (0/45) | | |
### Within-Laboratory Precision Study
Testing was conducted with FA Plus, FN Plus, SA and SN culture bottles in an in-house precision study for 20 days using multiple VIRTUO instruments and multiple operators. Three bottle replicates per organism, instrument, bottle type and bottle lot were tested for a minimum of 60 bottles tested for each organism and bottle lot. The target organism inoculum was less than 30 CFU/bottle. Bottles were tested without blood except for 1 mL of added blood for bottles spiked with B. fragilis and S. pneumoniae and 4 mL of added blood for bottles spiked with H. influenzae. The rate of detection and recovery as well as the mean time to detection was calculated for each organism and bottle type evaluated. For calculation of percent recovery, positive results reflect a positive flag by the instrument and Gram stain/subculture consistent with the seeded organism.
7
{7}
The within-laboratory precision study results were acceptable. Results are shown in Tables 3-6 for FA Plus, FN Plus, SA and SN culture bottles, respectively.
Table 3. FA Plus Bottles: Within-Laboratory Precision
| Sample Input Organism | Range (CFU/bottle) | % Recovery (# detected/# tested) | | | | Time to Detection (hours) | |
| --- | --- | --- | --- | --- | --- | --- | --- |
| | | Lot 1 | Lot 2 | Lot 3 | Overall | Mean | Range |
| *Candida albicans* | 3-30 | 100 (141/141) | 100 (144/144) | 100 (60/60) | 100 (345/345) | 27.1 | 21.4-40.0 |
| *Enterococcus faecalis* | 3-16 | 100 (162/162) | 100 (162/162) | 100 (60/60) | 100 (384/384) | 10.9 | 9.6-12.4 |
| *Escherichia coli* | 8-20 | 100 (153/153) | 100 (153/153) | 100 (60/60) | 100 (366/366) | 9.6 | 8.7-10.8 |
| *Haemophilus influenzae** | 1-24 | 100 (162/162) | 100 (162/162) | 100 (60/60) | 100 (384/384) | 13.6 | 11.0-21.6 |
| *Pseudomonas aeruginosa* | 5-17 | 100 (162/162) | 100 (162/162) | 100 (60/60) | 100 (384/384) | 14.7 | 12.8-17.6 |
| *Staphylococcus aureus* | 5-16 | 100 (171/171) | 100 (171/171) | 100 (60/60) | 100 (402/402) | 12.7 | 11.5-15.0 |
| *Streptococcus pneumoniae*** | 1-29 | 100 (162/162) | 100 (162/162) | 100 (60/60) | 100 (384/384) | 12.0 | 9.6-15.6 |
*Tested with 4 mL blood.
**Tested with 1 mL blood.
Table 4. FN Plus Bottles: Within-Laboratory Precision
| Sample Input Organism | Range (CFU/bottle) | % Recovery (# detected/# tested) | | | | Time to Detection (hours) | |
| --- | --- | --- | --- | --- | --- | --- | --- |
| | | Lot 1 | Lot 2 | Lot 3 | Overall | Mean | Range |
| *Bacteroides fragilis** | 4-33 | 100 (162/162) | 100 (163/163) | 100 (60/60) | 100 (385/385) | 24.5 | 21.8-26.7 |
| *Clostridium perfringens* | 4-16 | 100 (179/180) | 100 (177/178) | 100 (60/60) | 99.5 (416/418) | 9.9 | 8.4-14.5 |
| *Enterococcus faecalis* | 3-16 | 100 (160/160) | 100 (157/157) | 100 (60/60) | 100 (377/377) | 19.9 | 18.2-21.8 |
| *Escherichia coli* | 4-20 | 100 (154/154) | 100 (153/153) | 100 (60/60) | 100 (367/367) | 9.1 | 8.3-10.2 |
| *Staphylococcus aureus* | 5-16 | 100 (171/171) | 100 (171/171) | 100 (60/60) | 100 (402/402) | 17.4 | 15.4-19.9 |
| *Streptococcus pneumoniae** | 1-29 | 100 (162/162) | 100 (162/162) | 100 (60/60) | 100 (384/384) | 14.5 | 12.4-20.2 |
*Tested with 1 mL blood.
8
{8}
Table 5. SA Bottles: Within-Laboratory Precision
| Organism | Range (CFU/bottle) | % Recovery (# detected/# tested) | | | | Time to Detection (hours) | |
| --- | --- | --- | --- | --- | --- | --- | --- |
| | | Lot 1 | Lot 2 | Lot 3 | Overall | Mean | Range |
| *Candida albicans* | 10-30 | 100 (60/60) | 98.3 (59/60) | 100 (60/60) | 99.4 (179/180) | 25.5 | 21.0-30.1 |
| *Enterococcus faecalis* | 10-16 | 100 (60/60) | 100 (60/60) | 100 (60/60) | 100 (180/180) | 10.4 | 9.5-11.5 |
| *Escherichia coli* | 8-15 | 100 (60/60) | 100 (60/60) | 100 (60/60) | 100 (180/180) | 9.8 | 8.8-10.9 |
| *Haemophilus influenzae** | 14-24 | 100 (60/60) | 100 (60/60) | 100 (60/60) | 100 (180/180) | 17.8 | 9.2-23.8 |
| *Pseudomonas aeruginosa* | 7-17 | 100 (60/60) | 100 (60/60) | 100 (60/60) | 100 (180/180) | 14.2 | 13.0-16.0 |
| *Staphylococcus aureus* | 6-11 | 100 (60/60) | 100 (60/60) | 100 (60/60) | 100 (180/180) | 22.3 | 15.9-38.2 |
| *Streptococcus pneumoniae*** | 6-15 | 100 (60/60) | 100 (60/60) | 100 (60/60) | 100 (180/180) | 14.5 | 11.5-20.4 |
*Tested with 4 mL blood.
**Tested with 1 mL blood.
Table 6. SN Bottles: Within-Laboratory Precision
| Organism | Range (CFU/bottle) | % Recovery (# detected/# tested) | | | | Time to Detection (hours) | |
| --- | --- | --- | --- | --- | --- | --- | --- |
| | | Lot 1 | Lot 2 | Lot 3 | Overall | Mean | Range |
| *Bacteroides fragilis** | 12-33 | 100 (60/60) | 100 (60/60) | 100 (60/60) | 100 (180/180) | 26.2 | 19.7-38.9 |
| *Clostridium perfringens* | 10-15 | 100 (60/60) | 100 (60/60) | 100 (60/60) | 100 (180/180) | 7.9 | 6.4-39.7 |
| *Enterococcus faecalis* | 10-16 | 100 (60/60) | 100 (60/60) | 100 (60/60) | 100 (180/180) | 9.9 | 9.1-11.0 |
| *Escherichia coli* | 8-15 | 100 (60/60) | 100 (60/60) | 100 (60/60) | 100 (180/180) | 8.7 | 7.9-9.5 |
| *Staphylococcus aureus* | 6-11 | 100 (60/60) | 100 (60/60) | 100 (60/60) | 100 (180/180) | 12.8 | 11.3-14.5 |
| *Streptococcus pneumoniae** | 6-15 | 100 (60/60) | 100 (60/60) | 100 (60/60) | 100 (180/180) | 14.0 | 11.2-17.7 |
*Tested with 1 mL blood.
b. Traceability, Stability, Expected values (controls, calibrators, or methods):
### Quality Control
Internal Quality Control:
The VIRTUO system is designed with internal quality control/calibration. This is accomplished by automated comparison of optical readings to Reflectance Calibration Standards that reside in the VIRTUO instrument.
9
{9}
### External Quality Control:
During the clinical study, daily external quality control was conducted on the VIRTUO system and included one positive and one negative control bottle for each bottle type tested. Control organisms were seeded into bottles at target inoculum levels of approximately 30 CFU/bottle. Organism concentrations for bottle seeding were confirmed by plate counting procedures. For aerobic bottles, organisms evaluated included one obligate aerobe (*Pseudomonas aeruginosa*) and one facultative organism (*Escherichia coli*). For anaerobic bottles, organisms evaluated included one obligate anaerobe (*Clostridium perfringens*) and one facultative organism (*Escherichia coli*). For each bottle type, one organism was evaluated daily, alternating between the quality control two organisms. In addition, an uninoculated negative control bottle was tested daily for each bottle type. There were 1490 positive controls tested on VIRTUO for all clinical sites combined. Of those, 1487 (99.8%) generated the expected positive signal by VIRTUO. There were 1486 negative controls tested on VIRTUO for all sites combined and 100% were reported as negative.
#### c. Limit of Detection
The Limit of Detection (LoD) for FA Plus, FN Plus, SA and SN bottles was evaluated for bottles incubated on VIRTUO. The LoD for FA Plus and FN Plus was evaluated only on VIRTUO and compared to the LoD established previously on BTA 3D during studies performed for bottle clearance (i.e., K121461, K121455, K121446). The LoDs for SA and SN bottles had not been established on the BTA 3D; therefore LoD testing for SA and SN bottles was performed on both instrument systems. Because the media formulations are the same for FA Plus and PF Plus bottles, the LoD for FA Plus bottles is also claimed for PF Plus bottles.
Concentrations of organism suspensions used for bottle inoculation were determined by plating and colony counts. Each bottle was inoculated with organism suspensions prepare to yield 5 CFU/bottle. To support growth, human blood was added to bottles inoculated with *B. fragilis*, *S. pneumoniae*, and *H. influenzae*. Bottles were incubated on VIRTUO and BTA 3D instruments until flagged as positive. All bottles were subcultured and evaluated for growth, purity and presence of the appropriate test organism.
A total of 60 replicates were tested for each bottle type/microorganism combination (ten replicates for each of three bottle lots, tested on two VIRTUO instruments). Additionally, a total of 30 replicates were tested on one BTA 3D instrument for each SA and SN bottle type/microorganism combination.
The LoD for each organism/bottle type/instrument was determined to be the organism concentration (CFU/bottle) for which 95% of bottles were flagged positive by the instrument and were also positive by subculture. The LoDs for the organisms
10
{10}
evaluated in each bottle type are shown in Tables 7 for testing on VIRTUO and Table 8 for testing on BTA 3D.
Table 7. Organism LoD (CFU/Bottle) on VIRTUO
| | CFU/Bottle | | | |
| --- | --- | --- | --- | --- |
| | FA Plus/PF Plus | SA | FN Plus | SN |
| Candida albicans | 7 | 7 | | |
| E. faecalis | 4 | 4 | 3 | 3 |
| E. coli | 4 | 4 | 4 | 4 |
| H. influenzae* | 3 | 3 | | |
| P. aeruginosa | 8 | 8 | | |
| S. aureus | 3 | 3 | 6 | 6 |
| S. pneumoniae* | 3 | 3 | 5 | 5 |
| B. fragilis** | | | 4 | 4 |
| C. perfringens | | | 4 | 4 |
* 1 mL blood added
** 4 mL blood added
Table 8. Organism LoD (CFU/bottle) on BTA 3D
| | CFU/Bottle | | | |
| --- | --- | --- | --- | --- |
| | FA Plus/PF Plus*** | SA | FN Plus*** | SN |
| Aspergillus brasiliensis | | 4 | | |
| Candida albicans | 6 | 7 | | |
| E. faecalis | 4 | 4 | 4 | 3 |
| E. coli | 6 | 4 | 4 | 4 |
| H. influenzae* | 8 | 3 | | |
| P. aeruginosa | 5 | 8 | | |
| S. aureus | 3 | 3 | 4 | 6 |
| S. pneumoniae* | 4 | 3 | 6 | 5 |
| B. fragilis** | | | 5 | 4 |
| C. perfringens | | | 3 | 4 |
* 1 mL blood added
** 4 mL blood added
*** Note: LoD values determined previously for initial bottle clearance (K121461, K121455, K121446).
### d. Comparison Panel Growth Performance Study
The performance of the VIRTUO and BTA 3D systems were compared in an analytical study using a panel of microorganisms seeded into FA Plus, FN Plus, SA, and SN bottles. The growth performance study was conducted internally with seeded bottles containing two different blood volumes (4 and \(10~\mathrm{mL}\)). Seeded bottles without blood were also evaluated. A single strain was tested for each species evaluated at target inoculum levels of \(\leq 30\) CFU/bottle. Each microorganism was tested in triplicate for each bottle type and blood level on three VIRTUO systems for a total of 27 bottles per organism/bottle type. For BTA 3D, 9 bottles per blood level were tested on one system for a total of 27 bottles per organism and bottle type. Two positive bottles were subcultured per organism and
11
{11}
per bottle type to assess for purity. All seeded bottles that were declared negative by the instrument(s) were subcultured.
Tables 9 and 10 list the strains evaluated for the aerobic and anaerobic bottles in the Comparison Panel Growth Performance Study.
Table 9: Comparison Panel of Organisms for Aerobic Blood Culture Bottle (FA Plus and SA)
| Microorganism | ATCC # | Microorganism | ATCC # |
| --- | --- | --- | --- |
| Abiotrophia defectiva | 9497 | Micrococcus luteus | 4698 |
| Aggregatibacter actinomycetemcomitans | 29523 | Neisseria meningitidis | 13090 |
| Campylobacter jejuni | 33291 | Proteus vulgaris | 8427 |
| Candida albicans | 14053 | Pseudomonas aeruginosa | 27853 |
| Candida glabrata | 66032 | Salmonella enterica | 14028 |
| Candida krusei | 14243 | Serratia marcescens | 33949 |
| Cardiobacterium hominis | 500276 | Staphylococcus aureus | 25923 |
| Corynebacterium jeikeium | 14124 | Staphylococcus epidermidis | 12228 |
| Cryptococcus neoformans | 14116 | Stenotrophomonas maltophilia | 13637 |
| Eikenella corrodens | 102025 | Streptococcus agalactiae | 13813 |
| Enterobacter aerogenes | 13048 | Streptococcus mitis | 15914 |
| Enterococcus faecalis | 29212 | Streptococcus pneumoniae | 6305 |
| Escherichia coli | 25922 | Streptococcus pyogenes | 19615 |
| Haemophilus influenzae | 10211 | | |
| Klebsiella pneumoniae | 35657 | | |
| Listeria monocytogenes | 15313 | | |
Table 10: Comparison Panel of Organisms for Anaerobic Blood Culture Bottles (FN Plus and SN)
| Microorganism | ATCC # | Microorganism | ATCC # |
| --- | --- | --- | --- |
| Bacteroides fragilis | 25285 | Escherichia coli | 25922 |
| Bacteroides thetaiotaomicron | 29741 | Fusobacterium nucleatum | 25586 |
| Bacteroides vulgatus | 8482 | Parvimonas micra | 33270 |
| Clostridium perfringens | 13124 | Peptoniphilus asaccharolyticus | 14963 |
| Clostridium septicum | 400013 | Staphylococcus aureus | 25923 |
| Eggerthella lenta | 25559 | Streptococcus pneumoniae | 6305 |
| Enterococcus faecalis | 29212 | Streptococcus pyogenes | 19615 |
Tables 11-18 include stratified results for FA Plus, FN Plus, SA and SN bottles, tested either with blood or without blood added. For each bottle type, bottles were seeded with applicable organisms and incubated/monitored on both VIRTUO and BTA 3D systems.
12
{12}
Table 11: FA Plus Bottles: Growth Performance on BacT/ALERT VIRTUO and on BacT/ALERT 3D in Bottles Tested with Blood
| Organism | FA Plus BacT/ALERT VIRTUO With Blood | | | | FA Plus BacT/ALERT 3D With Blood | | | |
| --- | --- | --- | --- | --- | --- | --- | --- | --- |
| | % Recovery* (n) | Average CFU/Bottle | Mean TTD | Range TTD | % Recovery* (n) | Average CFU/bottle | Mean TTD | Range TTD |
| Abiotrophia defectiva | 100.0(18/18) | 23 | 15.1 | 14.2-16.1 | 100.0(12/12) | 15 | 22.0 | 19.0-28.6 |
| Aggregatibacter actinomycetemcomitans | 100.0(18/18) | 21 | 30.4 | 22.2-36.2 | 100.0(18/18) | 21 | 34.8 | 28.1-39.8 |
| Campylobacter jejuni | 100.0(18/18) | 7 | 40.2 | 34.2-50.2 | 100.0(18/18) | 7 | 44.6 | 37.7-54.5 |
| Candida albicans | 100.0(18/18) | 11 | 27.0 | 23.4-29.8 | 100.0(18/18) | 11 | 28.5 | 26.6-31.7 |
| Candida glabrata | 100.0(18/18) | 7 | 45.5 | 38.4-57.2 | 100.0(18/18) | 7 | 50.4 | 45.6-55.9 |
| Candida krusei | 100.0(18/18) | 20 | 17.1 | 16.1-17.9 | 100.0(18/18) | 20 | 19.1 | 18.7-19.7 |
| Cardiobacterium hominis | 100.0(18/18) | 12 | 45.6 | 39.7-52.4 | 100.0(18/18) | 12 | 57.6 | 50.9-65.5 |
| Corynebacterium jeikeium | 100.0(18/18) | 8 | 34.7 | 28.2-50.7 | 100.0(17/17) | 8 | 68.6 | 48.5-112.8 |
| Cryptococcus neoformans | 100.0(16/16) | 30 | 56.1 | 20.7-67.4 | 100.0(18/18) | 30 | 57.6 | 54.2-59.5 |
| Eikenella corrodens | 100.0(18/18) | 24 | 22.2 | 20.1-23.6 | 100.0(18/18) | 24 | 25.3 | 24.0-26.6 |
| Enterobacter aerogenes | 100.0(18/18) | 10 | 11.3 | 10.3-13.0 | 100.0(18/18) | 10 | 12.7 | 12.0-13.4 |
| Enterococcus faecalis | 100.0(18/18) | 11 | 10.3 | 9.4-11.0 | 100.0(18/18) | 11 | 12.3 | 12.0-13.0 |
| Escherichia coli | 100.0(18/18) | 9 | 9.3 | 8.6-10.1 | 100.0(18/18) | 9 | 11.1 | 9.1-11.8 |
| Haemophilus influenzae | 100.0(18/18) | 18 | 14.1 | 9.1-16.3 | 100.0(18/18) | 18 | 17.6 | 16.6-18.5 |
| Klebsiella pneumoniae | 100.0(18/18) | 9 | 9.7 | 8.8-10.4 | 100.0(18/18) | 9 | 11.9 | 11.5-12.2 |
| Listeria monocytogenes | 100.0(18/18) | 19 | 19.7 | 18.2-21.3 | 100.0(18/18) | 19 | 20.8 | 20.2-21.6 |
| Micrococcus luteus | 100.0(18/18) | 24 | 32.7 | 30.0-36.1 | 100.0(18/18) | 24 | 34.7 | 32.4-37.7 |
| Neisseria meningitidis | 100.0(18/18) | 8 | 20.4 | 18.0-23.8 | 100.0(18/18) | 8 | 22.4 | 20.4-25.0 |
| Proteus vulgaris | 100.0(18/18) | 22 | 11.8 | 11.0-12.5 | 100.0(18/18) | 22 | 13.6 | 13.2-13.9 |
| Pseudomonas aeruginosa | 100.0(18/18) | 12 | 14.4 | 13.8-15.2 | 100.0(18/18) | 12 | 16.8 | 16.3-18.0 |
| Salmonella enterica | 100.0(18/18) | 9 | 11.5 | 10.6-12.5 | 100.0(18/18) | 9 | 13.6 | 12.5-15.1 |
| Serratia marcescens | 100.0(18/18) | 10 | 11.4 | 10.7-12.3 | 100.0(18/18) | 10 | 13.2 | 12.5-14.2 |
| Staphylococcus aureus | 100.0(18/18) | 14 | 10.7 | 10.1-11.5 | 100.0(18/18) | 15 | 13.2 | 12.7-13.9 |
13
{13}
| Organism | FA Plus BacT/ALERT VIRTUO With Blood | | | | FA Plus BacT/ALERT 3D With Blood | | | |
| --- | --- | --- | --- | --- | --- | --- | --- | --- |
| | % Recovery* (n) | Average CFU/Bottle | Mean TTD | Range TTD | % Recovery* (n) | Average CFU/bottle | Mean TTD | Range TTD |
| Staphylococcus epidermidis | 100.0(18/18) | 11 | 15.9 | 14.1-18.0 | 100.0(18/18) | 11 | 17.7 | 16.6-18.7 |
| Stenotrophomonas maltophilia | 100.0(16/16) | 22 | 54.0 | 24.8-83.9 | 100.0(18/18) | 22 | 31.9 | 27.6-37.0 |
| Streptococcus agalactiae | 100.0(18/18) | 13 | 11.9 | 10.5-13.3 | 100.0(18/18) | 13 | 15.0 | 13.9-16.1 |
| Streptococcus mitis | 100.0(18/18) | 17 | 9.3 | 8.6-10.4 | 100.0(18/18) | 17 | 11.7 | 11.3-12.0 |
| Streptococcus pneumoniae | 100.0(18/18) | 22 | 11.4 | 10.6-12.1 | 100.0(18/18) | 22 | 13.7 | 13.4-14.2 |
| Streptococcus pyogenes | 100.0(18/18) | 16 | 10.4 | 9.8-10.9 | 100.0(18/18) | 16 | 12.4 | 11.5-13.0 |
*Percent Recovery = #detected/#tested
Table 12. FA Plus Bottles: Growth Performance on BacT/ALERT VIRTUO and on BacT/ALERT 3D in Bottles Tested with No Blood
| Organism | FA Plus BacT/ALERT VIRTUO No Blood | | | | FA Plus BacT/ALERT 3D No Blood | | | |
| --- | --- | --- | --- | --- | --- | --- | --- | --- |
| | % Recovery* (n) | Average CFU/Bottle | Mean TTD | Range TTD | % Recovery* (n) | Average CFU/bottle | Mean TTD | Range TTD |
| Abiotrophia defectiva | 100.0(3/3) | 15 | 34.6 | 27.8-41.8 | 100.0(5/5) | 15 | 32.5 | 25.4-47.5 |
| Aggregatibacter actinomycetemcomitans | 100.0(9/9) | 21 | 30.3 | 27.8-32.2 | 100.0(9/9) | 21 | 36.2 | 32.9-43.2 |
| Campylobacter jejuni | 100.0(6/6) | 7 | 45.8 | 40.2-52.0 | 100.0(9/9) | 7 | 49.2 | 47.3-51.4 |
| Candida albicans | 100.0(9/9) | 11 | 25.9 | 24.3-28.1 | 100.0(9/9) | 11 | 29.1 | 27.4-32.4 |
| Candida glabrata | 100.0(9/9) | 7 | 52.5 | 35.7-64.7 | 100.0(9/9) | 7 | 69.4 | 55.9-82.6 |
| Candida krusei | 100.0(9/9) | 20 | 20.6 | 17.9-22.0 | 100.0(9/9) | 20 | 22.5 | 20.6-24.2 |
| Cardiobacterium hominis | 100.0(9/9) | 12 | 55.3 | 52.8-59.1 | 0.0**(0/9) | 12 | N/A | N/A |
| Cryptococcus neoformans | 100.0(9/9) | 30 | 62.6 | 54.5-73.4 | 100.0(9/9) | 30 | 62.8 | 58.8-66.5 |
| Enterobacter aerogenes | 100.0(9/9) | 10 | 10.2 | 9.7-11.7 | 100.0(9/9) | 10 | 12.9 | 12.2-13.2 |
| Enterococcus faecalis | 100.0(9/9) | 11 | 10.2 | 9.4-10.9 | 100.0(9/9) | 11 | 13.5 | 13.2-13.9 |
| Escherichia coli | 100.0(9/9) | 9 | 8.8 | 8.3-9.9 | 100.0(9/9) | 9 | 11.4 | 10.8-11.8 |
14
{14}
| Klebsiella pneumoniae | 100.0 (9/9) | 9 | 9.7 | 9.1- 10.9 | 100.0 (9/9) | 9 | 12.3 | 12.0- 12.5 |
| --- | --- | --- | --- | --- | --- | --- | --- | --- |
| Listeria monocytogenes | 100.0 (9/9) | 19 | 18.7 | 17.2- 19.6 | 100.0 (9/9) | 19 | 20.2 | 19.7- 20.9 |
| Micrococcus luteus | 100.0 (9/9) | 24 | 31.8 | 31.1- 33.1 | 100.0 (9/9) | 24 | 35.4 | 34.8- 36.7 |
| Proteus vulgaris | 100.0 (9/9) | 22 | 10.8 | 10.2- 11.2 | 100.0 (9/9) | 22 | 13.3 | 13.0- 13.9 |
| Pseudomonas aeruginosa | 100.0 (9/9) | 12 | 14.9 | 14.1- 15.8 | 100.0 (9/9) | 12 | 18.4 | 17.8- 19.0 |
| Salmonella enterica | 100.0 (9/9) | 9 | 10.4 | 10.0- 10.9 | 100.0 (9/9) | 9 | 13.3 | 12.5- 13.9 |
| Serratia marcescens | 100.0 (9/9) | 10 | 11.3 | 10.9- 12.5 | 100.0 (9/9) | 10 | 13.8 | 13.0- 15.4 |
| Staphylococcus aureus | 100.0 (9/9) | 14 | 12.4 | 11.0- 13.3 | 100.0 (9/9) | 15 | 15.0 | 14.4- 16.6 |
| Staphylococcus epidermidis | 100.0 (9/9) | 11 | 17.9 | 16.4- 19.2 | 100.0 (9/9) | 11 | 20.9 | 20.4- 21.6 |
| Stenotrophomonas maltophilia | 100.0 (9/9) | 22 | 45.0 | 31.2- 56.9 | 100.0 (9/9) | 22 | 42.7 | 33.6- 63.8 |
| Streptococcus agalactiae | 100.0 (9/9) | 13 | 10.2 | 9.9- 10.8 | 100.0 (9/9) | 13 | 13.5 | 13.2- 13.9 |
| Streptococcus mitis | 100.0 (9/9) | 17 | 9.0 | 8.6-9.8 | 100.0 (9/9) | 17 | 12.6 | 12.0- 13.7 |
| Streptococcus pneumoniae | 100.0 (9/9) | 22 | 10.8 | 10.2- 11.5 | 100.0 (9/9) | 22 | 13.4 | 12.7- 14.2 |
| Streptococcus pyogenes | 100.0 (9/9) | 16 | 10.5 | 10.0- 11.9 | 100.0 (9/9) | 16 | 13.0 | 12.7- 13.4 |
*Recovery = #detected/#tested
**C. hominis was not detected in the absence of blood on the BacT/ALERT 3D (0/9). However, upon subculture of the negative C. hominis bottles to solid medium, pure growth was observed; therefore these bottles were considered false negative.
NOTE: Recovery of E. corrodens, H. influenzae, C. jeikeium, and N. meningitidis in FA Plus bottles, tested on either instrument, necessitate blood; therefore, FA Plus bottles not containing blood were excluded from analysis for these organisms. For these organisms, refer to Table 11 above for FA Plus Bottles containing blood.
15
{15}
Table 13. FN Plus Bottles: Growth Performance on BacT/ALERT VIRTUO and on BacT/ALERT 3D in Bottles Tested with Blood
| Organism | FN Plus BacT/ALERT VIRTUO With Blood | | | | FN Plus BacT/ALERT 3D With Blood | | | |
| --- | --- | --- | --- | --- | --- | --- | --- | --- |
| | % Recovery * (n) | Average CFU/Bottle | Mean TTD | Range TTD | % Recovery * (n) | Average CFU/bottle | Mean TTD | Range TTD |
| Bacteroides fragilis | 100.0(16/16) | 3 | 30.0 | 25.8-36.0 | 100.0(15/15) | 3 | 32.5 | 27.6-45.6 |
| Bacteroides thetaiotaomicron | 100.0(9/9) | 21 | 39.9 | 32.4-58.9 | 100.0(13/13) | 21 | 46.3 | 36.7-67.9 |
| Bacteroides vulgatus | 100.0(13/13) | 14 | 30.9 | 24.1-49.4 | 100.0(15/15) | 14 | 31.5 | 26.9-34.6 |
| Clostridium perfringens | 100.0(18/18) | 27 | 9.7 | 9.0-11.0 | 100.0(18/18) | 27 | 12.9 | 12.2-14.2 |
| Clostridium septicum | 100.0(18/18) | 14 | 11.2 | 9.8-14.9 | 100.0(18/18) | 14 | 15.4 | 13.7-22.3 |
| Eggerthella lenta | 100.0(18/18) | 18 | 33.5 | 27.9-43.2 | 88.9**(16/18) | 18 | 35.0 | 32.6-40.1 |
| Enterococcus faecalis | 100.0(18/18) | 11 | 11.8 | 10.5-13.1 | 100.0(18/18) | 11 | 14.7 | 13.0-25.0 |
| Escherichia coli | 100.0(18/18) | 9 | 9.2 | 8.6-9.5 | 100.0(18/18) | 9 | 11.3 | 11.0-12.0 |
| Fusobacterium nucleatum | 100.0(18/18) | 13 | 53.0 | 29.3-67.5 | 46.2***(6/13) | 13 | 81.0 | 43.4-108.5 |
| Parvimonas micra | 100.0(18/18) | 24 | 38.1 | 33.9-41.6 | 100.0(18/18) | 24 | 46.3 | 43.9-50.6 |
| Peptoniphilus asaccharolyticus | 100.0(18/18) | 7 | 48.9 | 38.8-61.7 | 100.0(18/18) | 7 | 53.2 | 49.2-62.9 |
| Staphylococcus aureus | 100.0(18/18) | 14 | 17.4 | 16.0-19.1 | 100.0(18/18) | 15 | 20.9 | 18.5-22.8 |
| Streptococcus pneumoniae | 100.0(18/18) | 22 | 14.2 | 12.3-23.0 | 100.0(18/18) | 22 | 16.4 | 15.1-25.4 |
| Streptococcus pyogenes | 100.0(18/18) | 16 | 11.4 | 10.1-13.9 | 100.0(18/18) | 16 | 14.0 | 12.0-16.6 |
*Percent Recovery = #detected/#tested
**Two FN Plus bottles spiked with Eggerthella lenta were called negative by BTA 3D. Growth was observed upon subculture; therefore these two bottles were considered false negative.
***Seven FN Plus bottles spiked with Fusobacterium nucleatum were called negative by BTA 3D. Five of these bottles were subcultured and no growth was observed.
16
{16}
Table 14. FN Plus Bottles: Growth Performance on BacT/ALERT VIRTUO and on BacT/ALERT 3D in Bottles Tested with No Blood
| Organism | FN Plus BacT/ALERT VIRTUO No Blood | | | | FN Plus BacT/ALERT 3D No Blood | | | |
| --- | --- | --- | --- | --- | --- | --- | --- | --- |
| | % Recovery* (n) | Average CFU/Bottle | Mean TTD | Range TTD | % Recovery * (n) | Average CFU/Bottle | Mean TTD | Range TTD |
| Bacteroides fragilis | 100.0 (6/6) | 3 | 39.1 | 36.9-44.7 | 100.0 (10/10) | 9 | 43.4 | 39.8-47.3 |
| Clostridium perfringens | 100.0 (9/9) | 27 | 10.1 | 8.9-10.9 | 100.0 (9/9) | 27 | 12.5 | 12.0-13.0 |
| Clostridium septicum | 100.0 (8/8) | 14 | 20.9 | 18.6-22.3 | 100.0 (9/9) | 14 | 26.3 | 25.7-26.6 |
| Eggerthella lenta | 100.0 (9/9) | 18 | 31.2 | 27.7-33.9 | 100.0 (9/9) | 18 | 33.4 | 31.0-34.8 |
| Enterococcus faecalis | 100.0 (9/9) | 11 | 22.0 | 19.6-23.7 | 100.0 (9/9) | 11 | 26.1 | 24.5-27.8 |
| Escherichia coli | 100.0 (9/9) | 9 | 9.4 | 9.0-9.7 | 100.0 (9/9) | 9 | 11.8 | 11.3-12.2 |
| Fusobacterium nucleatum | 100.0 (6/6) | 13 | 69.2 | 58.5-83.4 | 100.0 (5/5) | 13 | 94.0 | 73.7-113.5 |
| Peptoniphilus asaccharolyticus | 100.0 (8/8) | 7 | 93.5 | 82.6-111.0 | 100.0 (6/6) | 7 | 94.0 | 89.8-99.4 |
| Staphylococcus aureus | 100.0 (9/9) | 14 | 21.9 | 19.4-26.5 | 100.0 (9/9) | 15 | 22.4 | 21.6-23.5 |
| Streptococcus pneumoniae | 100.0 (9/9) | 22 | 35.4 | 24.3-44.4 | 100.0 (9/9) | 22 | 37.3 | 28.6-42.5 |
| Streptococcus pyogenes | 100.0 (9/9) | 16 | 31.5 | 28.2-34.5 | 100.0 (9/9) | 16 | 35.4 | 28.8-41.3 |
*Percent Recovery = #detected/#tested
NOTE: Recovery of B. thetaiotaomicron, B. vulgatus, and P. micra in FN Plus bottles, tested on either instrument without blood, did not yield sets of paired data. Therefore, FN Plus bottles not containing blood were excluded from this comparison analysis for these organisms.
Table 15. SA Bottles: Growth Performance on BacT/ALERT VIRTUO and on BacT/ALERT 3D in Bottles Tested with Blood
| Organism | SA BacT/ALERT VIRTUO With Blood | | | | SA BacT/ALERT 3D With Blood | | | |
| --- | --- | --- | --- | --- | --- | --- | --- | --- |
| | % Recovery* (n) | Average CFU/Bottle | Mean TTD | Range TTD | % Recovery* (n) | Average CFU/bottle | Mean TTD | Range TTD |
| Abiotrophia defectiva | 100.0 (18/18) | 23 | 15.9 | 14.5-18.0 | 100.0 (8/8) | 15 | 27.1 | 20.4-49.2 |
| Aggregatibacter actinomycetemcomitans | 100.0 (18/18) | 21 | 43.1 | 35.0-50.5 | 100.0 (18/18) | 21 | 47.5 | 42.2-52.1 |
| Aspergillus brasiliensis | 100.0 (18/18) | 12 | 46.2 | 39.4-55.4 | 100.0 (18/18) | 12 | 56.9 | 48.0-80.4 |
| Aspergillus fumigatus | 100.0 (18/18) | 25 | 30.9 | 28.6-34.8 | 100.0 (18/18) | 25 | 33.7 | 29.5-37.2 |
| Candida albicans | 100.0 (18/18) | 11 | 25.4 | 23.3-27.9 | 100.0 (18/18) | 11 | 25.5 | 24.2-27.1 |
| Candida glabrata | 100.0 (18/18) | 25 | 49.0 | 41.3-62.8 | 100.0 (18/18) | 25 | 57.3 | 52.8-63.8 |
17
{17}
| Organism | SA BacT/ALERT VIRTUO With Blood | | | | SA BacT/ALERT 3D With Blood | | | |
| --- | --- | --- | --- | --- | --- | --- | --- | --- |
| | % Recovery* (n) | Average CFU/Bottle | Mean TTD | Range TTD | % Recovery* (n) | Average CFU/bottle | Mean TTD | Range TTD |
| Candida krusei | 100.0(18/18) | 20 | 20.3 | 19.6-21.2 | 100.0(18/18) | 20 | 22.7 | 21.8-23.5 |
| Cardiobacterium hominis | 100.0(18/18) | 12 | 46.5 | 21.6-51.0 | 100.0(18/18) | 12 | 52.2 | 49.9-57.8 |
| Corynebacterium jeikeium | 100.0(18/18) | 8 | 30.9 | 29.3-33.9 | 100.0(18/18) | 8 | 33.5 | 31.9-36.0 |
| Cryptococcus neoformans | 100.0(18/18) | 30 | 58.8 | 48.9-70.1 | 100.0(18/18) | 30 | 58.8 | 52.3-69.8 |
| Eikenella corrodens | 100.0(18/18) | 24 | 22.9 | 21.7-23.8 | 100.0(18/18) | 24 | 27.0 | 26.2-28.3 |
| Enterobacter aerogenes | 100.0(18/18) | 10 | 10.9 | 9.9-11.9 | 100.0(18/18) | 10 | 13.3 | 12.5-14.4 |
| Enterococcus faecalis | 100.0(18/18) | 11 | 10.1 | 9.2-10.6 | 100.0(17/17) | 11 | 12.8 | 12.2-13.4 |
| Escherichia coli | 100.0(18/18) | 9 | 9.3 | 8.9-9.6 | 100.0(18/18) | 9 | 11.6 | 9.6-12.2 |
| Fusarium solani complex | 100.0(18/18) | 49 | 93.0 | 64.6-156.7 | 94.4(17/18)** | 49 | 88.4 | 74.4-111.1 |
| Haemophilus influenzae | 100.0(18/18) | 6 | 19.7 | 17.8-23.8 | 100.0(18/18) | 6 | 22.4 | 20.6-23.8 |
| Klebsiella pneumoniae | 100.0(18/18) | 9 | 9.8 | 9.3-10.2 | 100.0(18/18) | 9 | 12.2 | 11.8-12.7 |
| Listeria monocytogenes | 100.0(18/18) | 19 | 21.2 | 19.1-23.3 | 100.0(18/18) | 19 | 22.4 | 20.9-23.8 |
| Micrococcus luteus | 100.0(17/17) | 24 | 31.7 | 30.6-32.7 | 100.0(18/18) | 24 | 34.4 | 33.1-36.0 |
| Mucor circinelloides | 94.4(17/18) | 50 | 31.9 | 27.1-50.4 | 100.0(18/18) | 50 | 38.6 | 35.0-41.8 |
| Neisseria meningitidis | 100.0(34/34) | 12 | 18.7 | 16.1-21.4 | 100.0(35/35) | 13 | 22.2 | 20.6-24.7 |
| Proteus vulgaris | 100.0(18/18) | 22 | 11.6 | 10.7-12.0 | 100.0(18/18) | 22 | 14.3 | 13.9-14.6 |
| Pseudomonas aeruginosa | 100.0(18/18) | 12 | 13.7 | 9.2-14.9 | 100.0(18/18) | 12 | 17.7 | 17.3-18.2 |
| Salmonella enterica | 100.0(18/18) | 9 | 11.2 | 10.4-12.0 | 100.0(18/18) | 9 | 13.7 | 13.0-14.9 |
| Scedosporium apiospermum | 100.0(18/18) | 12 | 53.4 | 49.2-58.3 | 100.0(18/18) | 12 | 57.7 | 52.6-64.6 |
| Serratia marcescens | 100.0(18/18) | 10 | 11.6 | 10.8-13.0 | 100.0(18/18) | 10 | 18.6 | 10.6-98.2 |
| Staphylococcus aureus | 100.0(18/18) | 14 | 11.4 | 10.8-12.0 | 100.0(18/18) | 15 | 15.1 | 14.4-16.3 |
| Staphylococcus epidermidis | 100.0(18/18) | 11 | 17.0 | 15.9-18.1 | 100.0(18/18) | 11 | 19.8 | 19.0-21.6 |
| Stenotrophomonas maltophilia | 100.0(18/18) | 22 | 23.9 | 20.6-27.4 | 100.0(18/18) | 22 | 22.7 | 19.2-23.8 |
| Streptococcus agalactiae | 100.0(18/18) | 13 | 12.0 | 10.9-12.8 | 100.0(18/18) | 13 | 15.7 | 14.6-16.6 |
| Streptococcus mitis | 100.0(18/18) | 17 | 11.3 | 10.3-12.3 | 100.0(18/18) | 17 | 14.3 | 13.7-14.9 |
18
{18}
| Organism | SA BacT/ALERT VIRTUO With Blood | | | | SA BacT/ALERT 3D With Blood | | | |
| --- | --- | --- | --- | --- | --- | --- | --- | --- |
| | % Recovery* (n) | Average CFU/Bottle | Mean TTD | Range TTD | % Recovery* (n) | Average CFU/bottle | Mean TTD | Range TTD |
| Streptococcus pneumoniae | 100.0 (18/18) | 22 | 11.8 | 11.1-12.3 | 100.0 (18/18) | 22 | 15.0 | 14.4-15.6 |
| Streptococcus pyogenes | 100.0 (18/18) | 16 | 10.5 | 9.8-11.6 | 100.0 (18/18) | 16 | 13.3 | 13.0-13.7 |
* Percent Recovery = #detected/#tested
**Subculture of negative bottle resulted in no growth.
Table 16. SA Bottles: Growth Performance on BacT/ALERT VIRTUO and on BacT/ALERT 3D in Bottles Tested with No Blood
| Organism | SA BacT/ALERT VIRTUO No Blood | | | | SA BacT/ALERT 3D No Blood | | | |
| --- | --- | --- | --- | --- | --- | --- | --- | --- |
| | % Recovery* (n) | Average CFU/Bottle | Mean TTD | Range TTD | % Recovery* (n) | Average CFU/bottle | Mean TTD | Range TTD |
| Aggregatibacter actinomycetemcomitans | 100.0 (7/7) | 21 | 94.4 | 78.0-110.8 | 100.0 (8/8) | 21 | 82.3 | 67.9-106.1 |
| Aspergillus brasiliensis | 100.0 (9/9) | 12 | 46.0 | 41.2-50.1 | 100.0 (9/9) | 12 | 52.1 | 46.6-58.3 |
| Aspergillus fumigatus | 100.0 (9/9) | 25 | 28.2 | 24.9-30.0 | 100.0 (9/9) | 25 | 31.3 | 29.8-32.6 |
| Candida albicans | 100.0 (9/9) | 11 | 25.6 | 24.5-27.9 | 100.0 (9/9) | 11 | 26.8 | 25.9-27.6 |
| Candida glabrata | 100.0 (9/9) | 25 | 24.3 | 22.4-25.0 | 100.0 (9/9) | 25 | 26.4 | 25.4-27.4 |
| Candida krusei | 100.0 (9/9) | 20 | 23.3 | 21.9-24.3 | 100.0 (9/9) | 20 | 25.1 | 24.2-25.4 |
| Cryptococcus neoformans | 100.0 (8/8) | 30 | 87.7 | 79.1-108.2 | 100.0 (9/9) | 30 | 83.6 | 79.2-87.6 |
| Enterobacter aerogenes | 100.0 (9/9) | 10 | 9.8 | 9.3-10.3 | 100.0 (9/9) | 10 | 12.4 | 12.2-12.7 |
| Enterococcus faecalis | 100.0 (9/9) | 11 | 10.2 | 9.5-10.8 | 100.0 (9/9) | 11 | 13.4 | 13.0-13.7 |
| Escherichia coli | 100.0 (9/9) | 9 | 9.3 | 8.8-9.6 | 100.0 (9/9) | 9 | 12.6 | 12.2-13.2 |
| Fusarium solani complex | 100.0 (9/9) | 49 | 79.8 | 63.8-117.8 | 100.0 (9/9) | 49 | 77.9 | 72.7-86.2 |
| Klebsiella pneumoniae | 100.0 (9/9) | 9 | 9.9 | 9.6-10.2 | 100.0 (9/9) | 9 | 12.6 | 12.5-13.0 |
| Listeria monocytogenes | 100.0 (9/9) | 19 | 20.7 | 20.0-21.1 | 100.0 (9/9) | 19 | 23.3 | 22.8-23.8 |
| Micrococcus luteus | 100.0 (9/9) | 24 | 34.3 | 33.6-35.9 | 100.0 (9/9) | 24 | 37.1 | 36.2-38.2 |
| Mucor circinelloides | 100.0 (9/9) | 50 | 44.9 | 35.6-58.3 | 100.0 (9/9) | 50 | 54.0 | 47.0-63.4 |
| Proteus vulgaris | 100.0 | 22 | 11.0 | 10.5- | 100.0 | 22 | 13.9 | 13.7- |
19
{19}
| Organism | SA BacT/ALERT VIRTUO No Blood | | | | SA BacT/ALERT 3D No Blood | | | |
| --- | --- | --- | --- | --- | --- | --- | --- | --- |
| | % Recovery* (n) | Average CFU/Bottle | Mean TTD | Range TTD | % Recovery* (n) | Average CFU/bottle | Mean TTD | Range TTD |
| | (9/9) | | | 11.7 | (9/9) | | | 14.2 |
| Pseudomonas aeruginosa | 100.0 (9/9) | 12 | 14.5 | 13.6-15.0 | 100.0 (9/9) | 12 | 18.3 | 17.8-19.0 |
| Salmonella enterica | 100.0 (9/9) | 9 | 10.6 | 10.3-11.0 | 100.0 (9/9) | 9 | 13.5 | 13.0-14.2 |
| Scedosporium apiospermum | 100.0 (9/9) | 12 | 51.8 | 48.5-56.2 | 100.0 (9/9) | 12 | 58.0 | 53.8-60.5 |
| Serratia marcescens | 100.0 (9/9) | 10 | 10.6 | 10.1-11.0 | 100.0 (9/9) | 10 | 13.5 | 13.2-13.9 |
| Staphylococcus aureus | 100.0 (9/9) | 14 | 12.1 | 11.3-12.8 | 100.0 (9/9) | 15 | 15.8 | 14.9-17.0 |
| Staphylococcus epidermidis | 100.0 (9/9) | 11 | 18.8 | 18.1-19.8 | 100.0 (9/9) | 11 | 23.2 | 22.1-26.9 |
| Stenotrophomonas maltophilia | 100.0 (9/9) | 22 | 22.7 | 21.5-24.4 | 100.0 (9/9) | 22 | 24.3 | 23.3-25.0 |
| Streptococcus agalactiae | 100.0 (9/9) | 13 | 11.4 | 10.9-12.0 | 100.0 (9/9) | 13 | 15.5 | 15.1-15.8 |
| Streptococcus mitis | 100.0 (9/9) | 17 | 10.8 | 10.0-12.5 | 100.0 (9/9) | 17 | 14.8 | 14.6-15.1 |
| Streptococcus pneumoniae | 100.0 (9/9) | 22 | 14.3 | 13.4-15.4 | 100.0 (9/9) | 22 | 16.7 | 16.1-17.3 |
| Streptococcus pyogenes | 100.0 (9/9) | 16 | 14.2 | 12.5-15.4 | 100.0 (9/9) | 16 | 17.4 | 16.6-18.7 |
*Percent Recovery = #detected/#tested
NOTE: Recovery of A. defectiva, E. corrodens, H. influenzae, N. meningitidis and C. hominis in SA bottles, tested on either instrument, necessitate blood; therefore, SA bottles not containing blood were excluded from analysis for these organisms. For these organisms, refer to Table 15 above for results from bottles containing blood.
20
{20}
Table 17. SN Bottles: Growth Performance on BacT/ALERT VIRTUO and on BacT/ALERT 3D in Bottles Tested with Blood
| Organism | SN BacT/ALERT VIRTUO With Blood | | | | SN BacT/ALERT 3D With Blood | | | |
| --- | --- | --- | --- | --- | --- | --- | --- | --- |
| | % Recovery* (n) | Average CFU/Bottle | Mean TTD | Range TTD | % Recovery* (n) | Average CFU/bottle | Mean TTD | Range TTD |
| Bacteroides fragilis | 100.0(11/11) | 3 | 38.5 | 27.6-54.3 | 100.0(14/14) | 3 | 33.7 | 20.6-54.7 |
| Bacteroides thetaiotaomicron | 100.0(18/18) | 21 | 40.8 | 36.2-46.7 | 100.0(18/18) | 21 | 47.1 | 40.6-53.5 |
| Bacteroides vulgatus | 100.0(11/11) | 14 | 63.3 | 46.9-78.8 | 100.0(15/15) | 14 | 62.3 | 43.4-85.7 |
| Clostridium perfringens | 100.0(18/18) | 27 | 8.7 | 8.3-9.2 | 100.0(18/18) | 27 | 11.6 | 11.0-12.2 |
| Clostridium septicum | 100.0(18/18) | 21 | 9.8 | 9.0-10.7 | 100.0(18/18) | 21 | 12.9 | 12.0-13.4 |
| Eggerthella lenta | 88.2**(15/17) | 18 | 43.6 | 26.5-91.0 | 94.4**(17/18) | 18 | 40.8 | 19.7-57.4 |
| Enterococcus faecalis | 100.0(18/18) | 11 | 9.9 | 9.3-10.6 | 100.0(18/18) | 11 | 12.6 | 12.2-13.7 |
| Escherichia coli | 100.0(18/18) | 9 | 8.6 | 8.0-9.1 | 100.0(18/18) | 9 | 10.9 | 9.8-11.5 |
| Fusobacterium nucleatum | 100.0(18/18) | 13 | 32.8 | 13.8-50.0 | 100.0(18/18) | 13 | 39.7 | 21.4-53.8 |
| Parvimonas micra | 100.0(18/18) | 24 | 45.2 | 28.0-64.2 | 100.0(17/17) | 24 | 49.4 | 21.6-74.6 |
| Peptoniphilus asaccharolyticus | 100.0(18/18) | 7 | 33.1 | 27.8-39.3 | 100.0(18/18) | 7 | 42.5 | 36.2-58.3 |
| Staphylococcus aureus | 100.0(18/18) | 14 | 10.3 | 9.9-11.1 | 100.0(18/18) | 15 | 13.3 | 12.7-13.9 |
| Streptococcus pneumoniae | 100.0(18/18) | 22 | 11.9 | 11.3-12.6 | 100.0(18/18) | 22 | 15.1 | 14.4-15.8 |
| Streptococcus pyogenes | 100.0(18/18) | 16 | 9.7 | 9.1-10.3 | 100.0(18/18) | 16 | 12.2 | 11.3-12.7 |
* Percent Recovery = #detected/#tested
**Three SN bottles spiked with Eggerthella lenta were called negative by VIRTUO (2 bottles) and BTA 3D (1 bottle). Growth was observed upon subculture of all bottles; therefore these three bottles were considered false negatives.
21
{21}
Table 18. SN Bottles: Growth Performance on BacT/ALERT VIRTUO and on BacT/ALERT 3D in Bottles Tested with No Blood
| Organism | SN BacT/ALERT VIRTUO No Blood | | | | SN BacT/ALERT 3D No Blood | | | |
| --- | --- | --- | --- | --- | --- | --- | --- | --- |
| | % Recovery* (n) | Average CFU/Bottle | Mean TTD | Range TTD | % Recovery* (n) | Average CFU/bottle | Mean TTD | Range TTD |
| Bacteroides fragilis | 100.0(9/9) | 3 | 25.0 | 23.3-28.5 | 100.0(8/8) | 3 | 29.5 | 28.8-30.0 |
| Bacteroides thetaiotaomicron | 100.0(9/9) | 21 | 25.5 | 23.7-27.3 | 100.0(9/9) | 21 | 29.5 | 28.3-31.7 |
| Bacteroides vulgatus | 100.0(9/9) | 14 | 27.2 | 25.6-28.3 | 100.0(9/9) | 14 | 31.4 | 31.0-32.4 |
| Clostridium perfringens | 100.0(9/9) | 27 | 8.0 | 7.7-8.5 | 100.0(9/9) | 27 | 10.9 | 10.6-11.3 |
| Clostridium septicum | 100.0(9/9) | 21 | 12.0 | 10.4-15.1 | 100.0(9/9) | 21 | 16.5 | 15.1-18.2 |
| Eggerthella lenta | 100.0(8/8) | 18 | 24.5 | 23.2-25.7 | 100.0(9/9) | 18 | 27.5 | 27.1-28.3 |
| Enterococcus faecalis | 100.0(9/9) | 11 | 9.4 | 8.9-10.2 | 100.0(9/9) | 11 | 12.6 | 12.2-13.0 |
| Escherichia coli | 100.0(9/9) | 9 | 8.3 | 7.9-9.0 | 100.0(9/9) | 9 | 11.0 | 10.6-11.8 |
| Fusobacterium nucleatum | 100.0(8/8) | 13 | 28.3 | 24.9-31.5 | 100.0(9/9) | 13 | 42.0 | 34.8-49.2 |
| Parvimonas micra | 100.0(8/8) | 24 | 38.0 | 36.3-40.2 | 100.0(9/9) | 24 | 43.8 | 42.0-45.1 |
| Peptoniphilus asaccharolyticus | 100.0(9/9) | 7 | 29.2 | 28.1-31.5 | 100.0(9/9) | 7 | 37.1 | 35.5-38.9 |
| Staphylococcus aureus | 100.0(9/9) | 14 | 11.4 | 11.0-12.0 | 100.0(9/9) | 15 | 15.2 | 14.9-15.6 |
| Streptococcus pneumoniae | 100.0(9/9) | 22 | 14.3 | 13.3-15.4 | 100.0(9/9) | 22 | 17.2 | 16.3-17.8 |
| Streptococcus pyogenes | 100.0(9/9) | 16 | 10.4 | 9.5-11.7 | 100.0(9/9) | 16 | 13.5 | 13.0-14.4 |
*Percent Recovery = #detected/#tested
In summary, results of the Growth Performance study demonstrated equivalent performance for VIRTUO and BTA 3D systems for detection and recovery of representative organisms in FA Plus, FN Plus, SA and SN bottles. The study demonstrated 100% detection for the majority of organisms evaluated in each bottle type. The following differences in detection were observed between instruments:
- FA Plus bottles, Cardiobacterium hominis (without blood): 0/9 detected on BTA 3D, 9/9 detected on VIRTUO
- FN Plus bottles, Eggerthella lenta (with blood): 16/18 bottles detected on BTA 3D, 18/18 detected on VIRTUO
- FN Plus bottles, Fusobacterium nucleatum (with blood): 6/13 bottles detected on BTA 3D, 18/18 detected on VIRTUO.
- SA bottles, Fusarium solani complex (with blood): 17/18 bottles detected on BTA 3D, 18/18 detected on VIRTUO.
22
{22}
- SN bottles, Eggerthella lenta (without blood): 17/18 bottles detected on BTA 3D, 15/17 bottles detected on VIRTUO.
# e. Evaluation of Delay in Bottle Entry
As stated in the labeling for FA Plus, FN Plus, PF Plus, SA and SN bottles, it is recommended that bottles are loaded onto the instrument as soon as possible. If a delay is inevitable, it is recommend that bottles should be held at room temperature for no longer than 24 hours. The following statement is also included in each bottle package insert:
* CAUTION: Culture bottles held at room temperature for longer than 24 hours before loading may not detect microorganisms and should be subcultured.
An analytical study was performed to evaluate potential effects on bottle/instrument performance for bottles that are delayed between specimen collection and loading onto the VIRTUO system. The following delay conditions were evaluated:
- 2-8°C for 48 hours
- 20-25°C for 24 hours
- 20-25°C for 36 hours
- 35- 37°C for 8 hours
Testing was conducted using bottles containing 0, 4 and/or 10 mL pooled fresh human blood at target organism concentrations of ≤100 CFU/bottle. The study included three lots for each bottle type and a minimum of nine bottles for each combination of bottle type, organism, hold time, temperature condition and blood volume. Percent recovery reflects bottles flagged positive by the instrument and subculture with colony morphology consistent with the seeded organism.
# FA Plus Bottles/Delayed Entry (VIRTUO):
For FA Plus bottles tested on VIRTUO, 9 species were evaluated (Staphylococcus aureus, Candida albicans, Escherichia coli, Acinetobacter baumannii, Pseudomonas aeruginosa, Haemophilus influenzae, Neisseria meningitidis, Streptococcus pneumoniae, and Enterococcus faecium) at target concentrations of ≤100 CFU/bottle. Actual inoculum levels ranged from 5-84 CFU/bottle. The study demonstrated >99% recovery with the exception of culture bottles held at 2-8°C for 48 hours for which 12 of 13 bottles spiked with N. meningitidis were negative. The study results are shown in Table 19 below.
23
{23}
Table 19. FA Plus Bottles: Delayed Entry (VIRTUO)
| Sample Input | Incubation Temperature (°C) | Hold Time (hours) | % Recovery (# detected/# tested) | Time to Detection from Sample Inoculation (Hold Time + Instrument TTD in hours) | |
| --- | --- | --- | --- | --- | --- |
| | | | | Mean | Range |
| Inoculated Test Bottles | Control | No delay | 100 (539/539) | 14.0 | 8.5-40.5 |
| | 35-37 | 8 | 99.8 (538/539) | 17.0 | 10.7-37.4 |
| | 20-25 | 24 | 100 (539/539) | 33.3 | 27.4-78.8 |
| | 20-25 | 36 | 99.8 (535/536) | 43.7 | 37.5-130.1 |
| | 2-8 | 48 | 97.6 (519/532)* | 62.5 | 56.9-87.5 |
| Negative Controls | All conditions | | 0 (0/64)^{†} | - | - |
*12 Negative bottles out of 13 were observed when tested with N. meningitidis
† Negative controls tested with 10 mL human blood
# FN Plus/Delayed Entry (VIRTUO):
For FN Plus bottles tested on VIRTUO, 6 species were evaluated (Staphylococcus aureus, Escherichia coli, Streptococcus pneumoniae, Enterococcus faecium, Bacteroides fragilis, and Clostridium perfringens) at target concentrations of ≤100 CFU/bottle. Actual inoculum levels ranged from 9-84 CFU/bottle. For all organisms and delay conditions evaluated, study results demonstrated 100% recovery. The study results are shown in Table 20 below.
24
{24}
**Table 20. FN Plus Bottles: Delayed Entry (VIRTUO)**
| Sample Input | Incubation Temperature (°C) | Hold Time (hours) | % Recovery (# detected/ # tested) | Time to Detection from Sample Inoculation (Hold Time + Instrument TTD in hours) | |
| --- | --- | --- | --- | --- | --- |
| | | | | Mean | Range |
| Inoculated Test Bottles | Control | No delay | 100.0 (144/144) | 16.0 | 9.1-40.5 |
| | 2-8 | 48 | 100.0 (141/141) | 65.1 | 56.9-87.5 |
| | 20-25 | 24 | 100.0 (143/143) | 37.0 | 27.5-78.8 |
| | 20-25 | 36 | 100.0 (141/141) | 48.1 | 37.9-130.1 |
| | 35-37 | 8 | 100.0 (143/143) | 18.9 | 10.8-37.4 |
| Negative Controls | All conditions | | 0.0 (0/30) | - | - |
### SA Bottles/Delayed Entry (VIRTUO)
For SA bottles tested on VIRTUO, 11 species (*Staphylococcus aureus*, *Candida albicans*, *Candida krusei*, *Escherichia coli*, *Klebsiella pneumoniae*, *Acinetobacter baumannii*, *Pseudomonas aeruginosa*, *Haemophilus influenzae*, *Neisseria meningitidis*, *Streptococcus pneumoniae*, and *Enterococcus faecium*) were evaluated at target concentrations of ≤100 CFU/bottle. Actual inoculum levels ranged from 4-51 CFU/bottle. The study results support the bottle performance for the recommended delay conditions of 24 hours at room temperature with the exception of bottles seeded with *N. meningitidis*. For this condition, 17/18 bottles spiked with *N. meningitidis* were unexpectedly negative. It was noted however that 18/18 SA bottles with *N. meningitidis* were positive when tested after a 36 hour delay at room temperature. It was thought that the unexpected negative results for the 24 hour/room temperature condition were due to inoculation errors and it was determined that repeat testing would not be necessary. The study results are shown in Table 21 below.
**Table 21. SA Bottles: Delayed Entry VIRTUO**
| Sample Input | Incubation Temperature (°C) | Hold Time (hours) | % Recovery (# detected/ # tested) | Time to Detection from Sample Inoculation (Hold Time + Instrument TTD in hours) | |
| --- | --- | --- | --- | --- | --- |
| | | | | Mean | Range |
| Inoculated Test Bottles | Control | No delay | 99.4 (307/309) | 15.7 | 9.4 - 36.4 |
| | 35-37 | 8 | 99.7 (306/307) | 17.5 | 11.2 – 79.3 |
| | 20-25 | 24 | 94.4 (289/306)* | 33.2 | 27.1 – 55.4 |
| | 20-25 | 36 | 99.3 (303/305) | 44.0 | 37.5 – 88.8 |
| | 2-8 | 48 | 87.5 (266/304)** | 63.8 | 56.3 – 85.8 |
| Negative Controls | All conditions | | 0/50 | - | - |
*17/18 bottles with *N. meningitidis* were negative for the 24 hour room temperature delay condition. 18/18 bottles with *N. meningitidis* were recovered at 36 hour room temperature delay condition. Therefore, results at 24 hours are likely due to issues with bottle inoculation.
** 17/18 bottles with *N. meningitidis* were negative for the 48 hour 2-8°C delay condition
25
{25}
SN Bottles/Delayed Entry (VIRTUO): For SN bottles tested on VIRTUO, 6 species were evaluated (Staphylococcus aureus, Escherichia coli, Streptococcus pneumoniae, Enterococcus faecium, Bacteroides fragilis, and Clostridium perfringens) at target concentrations of ≤100 CFU/bottle. Actual inoculum levels ranged from 9-84 CFU/bottle. For all organisms and delay conditions evaluated, study results demonstrated 100% recovery. The study results are shown in Table 22 below.
Table 22. SN Bottles, Delayed Entry
| Sample Input | Incubation Temperature (°C) | Hold Time (hours) | % Recovery (# detected/# tested) | Time to Detection from Sample Inoculation (Hold Time + Instrument TTD in hours) | |
| --- | --- | --- | --- | --- | --- |
| | | | | Mean | Range |
| Inoculated Test Bottles | Control | No delay | 100.0 (144/144) | 16.0 | 9.1-40.5 |
| | 2-8 | 48 | 100.0 (141/141) | 65.1 | 56.9-87.5 |
| | 20-25 | 24 | 100.0 (143/143) | 37.0 | 27.5-78.8 |
| | 20-25 | 36 | 100.0 (141/141) | 48.1 | 37.9-130.1 |
| | 35-37 | 8 | 100.0 (143/143) | 18.9 | 10.8-37.4 |
| Negative Controls | All conditions | | 0.0 (0/30) | - | - |
# f. Interfering Substances
An in-house study was conducted to evaluate FA Plus and FN Plus bottles on VIRTUO for the effect of potentially interfering substance. Seeded studies were conducted with CSF, pleural fluid, synovial fluid, plasma, and blood. Potential interferents included WBC at ~1 x 10⁷/mL as well as blood clots. Testing included bottles without organism as well as bottles seeded with organism concentrations between 65 and 120 CFU/bottle. A total of five bottles were evaluated for each bottle type, microorganism, specimen type, and interfering substance combination shown in Table 23 below.
Table 23: Interference Testing
| Sterile Body Fluid | Category per CLSI H56-A | Test Organism(s) | Supplements | Bottles Tested |
| --- | --- | --- | --- | --- |
| Peritoneal Fluid | Serous | Staphylococcus aureus and Streptococcus pneumoniae | WBC and Clots | FA Plus and FN Plus |
| Synovial (Joint) Fluid | Synovial | Staphylococcus aureus | WBC and Clots | FA Plus and FN Plus |
| Cerebrospinal Fluid | Cerebral spinal fluid and Ventricular shunt Fluids | Neisseria meningitidis* | WBC and Clots | FA Plus |
26
{26}
| Blood | N/A | Staphylococcus aureus | WBC and Clots | FA Plus and FN Plus |
| --- | --- | --- | --- | --- |
| Plasma | N/A | Staphylococcus aureus | None | FA Plus and FN Plus |
*Note: 4 mL blood added
Testing of each bottle type, specimen type, microorganism and potentially interfering substance generated 100% of the expected positive and negative results. In addition, the time to detection for each specimen type and bottle was not significantly impacted by the presence of WBC or blood clots.
g. Assay cut-off:
Not Applicable
#### 2. Comparison studies:
Method comparison with predicate device:
### Section M.2.1: Clinical Study to Evaluate Blood Cultures on VIRTUO and BTA 3D
A multi-center clinical study was conducted to compare the performance of the VIRTUO and BTA 3D Systems with blood cultures collected in FA Plus, FN Plus, PF Plus, SA, and SN culture bottles. The study included evaluation of matched pairs of the same bottle type with one bottle incubated on BTA 3D and the other incubated on VIRTUO. For each bottle type, the performance of VIRTUO was considered substantially equivalent to the BTA 3D if the upper limit of the 95% confidence interval for the ratio of system agreement with positive clinical determination (true positive rate) for the total compliant samples/isolates (significant, contaminated and unknown) contained a value of 1.
The target quantity for adult bottles (FA Plus, FN Plus, SA and SN) was 8-10 mL per bottle and overfilled bottle test pairs (either bottle) of an adult pair with a volume greater than the maximum 10ml blood fill were excluded from the analysis. For purposes of data analysis, the paired bottles for adult blood culture bottles were considered compliant if the blood volume of the bottle with the smallest volume was within 30% of the blood volume of the bottle with the largest volume.
The target quantity for pediatric bottles (PF Plus) was 4 mL per bottle. PF Plus blood culture bottle pairs were considered compliant if the following criteria were met:
(a) if the total volume of blood collected from a pediatric patient was greater than 5 mL, the blood volume of the bottle with the smallest volume is within 20% of the blood volume of the bottle with the larger volume or
27
{27}
(b) if the total volume of blood collected from a pediatric patient was equal to or less than 5 mL, the blood volume of the bottle with the smallest volume is within 50% of the blood volume of the bottle with the largest volume.
Overfilled bottle test pairs (either bottle) of a PF Plus bottle pair with a volume greater than the maximum 4ml blood fill were excluded from the analysis. All bottles that were flagged as positive by the instrument were subcultured and a minimum of 30% of all negative blood cultures were subcultured. A culture bottle was determined to be a “True Positive” if flagged positive by the instrument and if an isolate or isolates were recovered by subculture. True positive rates were calculated for each bottle and specimen type on BTA 3D and on VIRTUO, and the ratio of VIRTUO true positives to BTA 3D true positives was calculated to compare performance between instruments. Clinical isolates recovered from each subcultured bottle were classified as significant, contaminant, or unknown. Classification was performed by clinicians at each clinical site and was based on patient chart review in conjunction with predetermined criteria.
A culture bottle was determined to be false negative if the bottle result was negative by the instrument and resulted in growth upon subculture of the bottle.
A culture bottle was determined to be false positive if the instrument signaled the bottle as positive but no viable organisms were present in the bottle as confirmed by Gram stain and subculture.
Results are shown below for blood culture specimens collected in FA Plus, FN Plus, PF Plus, SA and SN bottle pairs of which one bottle was tested on VIRTUO and the other bottle was tested on BTA 3D.
### **Section M.2.1.a- FA Plus Bottles (Blood Cultures) Clinical Performance:**
A total of 1441 FA Plus bottle pairs obtained from 750 adult patients suspected of blood stream bacterial/yeast infections were tested on both VIRTUO and BTA 3D. Of these, 1053 bottle pairs from 637 patients were determined as compliant.
A total of 98 isolates were recovered from all compliant FA Plus bottle pairs with a positive status. At least one isolate was recovered by subculture from 94 FA Plus bottle pairs incubated on VIRTUO and/or BTA 3D. Two isolates were recovered from two bottle pairs and three isolates were recovered from one bottle pair. A total of 73 isolates were recovered from FA Plus bottles on VIRTUO and a total of 79 isolates were recovered from FA Plus bottles on BTA 3D. Of the significant isolates, a total of 64 isolates were recovered from FA Plus bottles on VIRTUO compared to a total of 66 isolates recovered from FA Plus bottles on BTA 3D.
No false positives FA Plus bottles were observed on VIRTUO (0/1057) or BTA 3D (0/1057).
Terminal subcultures were performed for 624 FA Plus bottle pairs that were negative on
28
{28}
both VIRTUO and BTA 3D. False negative results were observed for both bottles of one bottle pair. For negative bottle pairs for which both bottles were subcultured, the final false negative rate was 0.16% for both instruments.
The following tables compare results of true positive blood cultures incubated on VIRTUO and BTA 3D for all compliant FA Plus culture bottles yielding any number of isolates on subculture (Table 24), a single isolate on subculture (Table 25), and multiple isolates on subculture (Table 26).
**Table 24. FA Plus - Blood – Compliant – Single and Multiple Isolates Combined**
| Clinical Determination | VIRTUO True Positives | % of VIRTUO True Positives in Population | BTA3D True Positives | % of BTA3D True Positives in Population | Ratio of True Positives (VIRTUO /BTA3D) | 95% CI (LCL, UCL) |
| --- | --- | --- | --- | --- | --- | --- |
| Significant | 64 | 6.1 (64/1057) | 66 | 6.2 (66/1057) | 0.970 | 0.821, 1.119 |
| Contaminant | 7 | 0.7 (7/1057) | 11 | 1.0 (11/1057) | 0.636 | * |
| Unknown | 2 | 0.2 (2/1057) | 2 | 0.2 (2/1057) | 1.000 | * |
| Total | 73 | 6.9 (73/1057) | 79 | 7.5 (79/1057) | 0.924 | 0.766, 1.082 |
* Confidence intervals not calculated due to small sample size.
**Table 25. FA Plus - Blood – Single Isolates**
| Clinical Determination | VIRTUO True Positives | % of VIRTUO True Positives in Population | BTA3D True Positives | % of BTA3D True Positives in Population | Ratio of True Positives (VIRTUO /BTA3D) | 95% CI (LCL, UCL) |
| --- | --- | --- | --- | --- | --- | --- |
| Significant | 57 | 5.4 (57/1050) | 60 | 5.7 (60/1050) | 0.950 | 0.791, 1.109 |
| Contaminant | 7 | 0.7 (7/1050) | 11 | 1.0 (11/1050) | 0.636 | * |
| Unknown | 2 | 0.2 (2/1050) | 2 | 0.2 (2/1050) | 1.000 | * |
| Total | 66 | 6.3 (66/1050) | 73 | 7.0 (73/1050) | 0.904 | 0.737, 1.071 |
* Confidence intervals not calculated due to small sample size.
29
{29}
Table 26. FA Plus - Blood – Multiple Isolates
| Clinical Determination | VIRTUO True Positives | % of VIRTUO True Positives in Population | BTA3D True Positives | % of BTA3D True Positives in Population | Ratio of True Positives (VIRTUO /BTA3D) | 95% CI (LCL, UCL) |
| --- | --- | --- | --- | --- | --- | --- |
| Significant | 7 | 100.0 (7/7) | 6 | 85.7 (6/7) | 1.167 | 0.814, 1.520 |
| Contaminant | 0 | 0.0 (0/7) | 0 | 0.0 (0/7) | - | * |
| Unknown | 0 | 0.0 (0/7) | 0 | 0.0 (0/7) | - | * |
| Total | 7 | 100.0 (7/7) | 6 | 85.7 (6/7) | 1.167 | 0.814, 1.520 |
* Confidence intervals not calculated due to small sample size.
Table 27 includes the comparative yield of microorganisms (number of isolates) recovered on subculture from FA Plus bottles incubated on VIRTUO and BTA 3D.
Table 27: FA Plus: Comparative Yield of Microorganisms (Number of Isolates) – Blood Cultures
| Group | BacT/ALERT VIRTUO | BacT/ALERT 3D |
| --- | --- | --- |
| Anaerobes | 2 | 0 |
| Enterobacteriaceae | 18 | 18 |
| Enterococcus spp. | 7 | 7 |
| Yeasts | 3 | 1 |
| Non-fermentative Gram-Negative Bacilli | 6 | 5 |
| Other Gram-Negative | 0 | 1 |
| Other Gram-Positive | 1 | 5 |
| Coagulase-Negative Staphylococcus | 12 | 16 |
| Staphylococcus aureus | 16 | 19 |
| Streptococcus spp. | 7 | 6 |
| Other | 1 | 1 |
| All | 73 | 79 |
Note: Table includes polymicrobic cultures
### Section M.21.b- FN Plus Bottles (Blood) Clinical Performance:
A total of 1181 FN Plus bottle pairs, obtained from 582 adult patients suspected of blood stream bacterial/yeast infections were tested on both VIRTUO and BTA 3D. Of these, 906 bottle pairs from 513 patients were determined as compliant.
A total of 73 isolates were recovered from all compliant FN Plus Culture Bottle pairs with a positive status. At least one isolate was recovered by subculture from 67 bottle pairs incubated on VIRTUO or BTA 3D respectively. A single isolate was recovered from 62 bottle pairs, two isolates were recovered from four bottle pairs, and three isolates were recovered from one bottle pair.
A total of 60 isolates were recovered from FN Plus bottles on VIRTUO and a total of 58 isolates were recovered from FN Plus bottles on BTA 3D. Of the significant isolates, the
30
{30}
VIRTUO FN Plus bottles detected a total of 47 isolates compared to the BTA 3D FN Plus bottles which detected 48 isolates.
Two false positive FN Plus bottles were observed on VIRTUO (2/912, 0.22%) and one false positive FN Plus Culture Bottle was observed on BTA 3D (1/912, 0.11%).
Terminal subcultures were performed for 593 FN Plus bottle pairs that were negative on both VIRTUO and BTA 3D. A total of six false negative bottles were observed for FN Plus bottles on both VIRTUO and BTA 3D. For negative bottle pairs for which both bottles were subcultured, the final false negative rate was 1.01% (6/593) for both instruments.
The following tables compare true positive results of blood cultures incubated on VIRTUO and BTA 3D for all compliant FN Plus blood culture bottles yielding any number of isolates on subculture (Table 28), a single isolate on subculture (Table 29), and multiple isolates on subculture (Table 30).
**Table 28. FN Plus – Blood – Compliant – Single and Multiple Isolates Combined**
| Clinical Determination | VIRTUO True Positives | % of VIRTUO True Positives in Population | BTA3D True Positives | % of BTA3D True Positives in Population | Ratio of True Positives (VIRTUO /BTA3D) | 95% CI (LCL, UCL) |
| --- | --- | --- | --- | --- | --- | --- |
| Significant | 47 | 5.2 (47/912) | 48 | 5.3 (48/912) | 0.979 | 0.823, 1.135 |
| Contaminant | 13 | 1.4 (13/912) | 10 | 1.1 (10/912) | 1.300 | * |
| Unknown | 0 | 0.0 (0/912) | 0 | 0.0 (0/912) | - | * |
| Total | 60 | 6.6 (60/912) | 58 | 6.4 (58/912) | 1.034 | 0.852, 1.216 |
* Confidence intervals not calculated due to small sample size.
**Table 29. FN Plus – Blood – Single Isolates**
| Clinical Determination | VIRTUO True Positives | % of VIRTUO True Positives in Population | BTA3D True Positives | % of BTA3D True Positives in Population | Ratio of True Positives (VIRTUO /BTA3D) | 95% CI (LCL, UCL) |
| --- | --- | --- | --- | --- | --- | --- |
| Significant | 39 | 4.3 (39/901) | 43 | 4.8 (43/901) | 0.907 | 0.757, 1.057 |
| Contaminant | 10 | 1.1 (10/901) | 7 | 0.8 (7/901) | 1.429 | * |
| Unknown | 0 | 0.0 (0/901) | 0 | 0.0 (0/901) | - | * |
| Total | 49 | 5.4 (49/901) | 50 | 5.5 (50/901) | 0.980 | 0.786, 1.174 |
* Confidence intervals not calculated due to small sample size.
31
{31}
Table 30. FN Plus – Blood – Multiple Isolates
| Clinical Determination | VIRTUO True Positives | % of VIRTUO True Positives in Population | BTA3D True Positives | % of BTA3D True Positives in Population | Ratio of True Positives (VIRTUO /BTA3D) | 95% CI (LCL, UCL) |
| --- | --- | --- | --- | --- | --- | --- |
| Significant | 8 | 72.7 (8/11) | 5 | 45.5 (5/11) | 1.600 | 0.741, 2.459 |
| Contaminant | 3 | 27.3 (3/11) | 3 | 27.3 (3/11) | 1.000 | * |
| Unknown | 0 | 0.0 (0/11) | 0 | 0.0 (0/11) | - | * |
| Total | 11 | 100.0 (11/11) | 8 | 72.7 (8/11) | 1.375 | 0.877, 1.873 |
* Confidence intervals not calculated due to small sample size.
Table 31 includes the comparative yield of microorganisms (number of isolates) recovered on subculture from FN Plus bottles incubated on VIRTUO and BTA3D.
Table 31. FN Plus: Comparative Yield of Microorganisms (Number of Isolates) – Blood Cultures
| Group | BacT/ALERT VIRTUO | BacT/ALERT 3D |
| --- | --- | --- |
| Anaerobes | 1 | 1 |
| Enterobacteriaceae | 22 | 19 |
| Enterococcus spp. | 6 | 6 |
| Yeasts | - | - |
| Non-fermentative Gram-Negative Bacilli | - | - |
| Other Gram-Positive | - | - |
| Coagulase-Negative Staphylococcus | 13 | 11 |
| Staphylococcus aureus | 12 | 13 |
| Streptococcus spp. | 6 | 8 |
| All | 60 | 58 |
NOTE: Isolate table includes polymicrobic cultures.
### Section M.2.1.c- PF Plus Bottles (Blood) Clinical Performance:
A total of 202 PF Plus bottle pairs, obtained from 73 pediatric patients suspected of blood stream bacterial/yeast infections were tested on both VIRTUO and BTA 3D instruments. Of these, 161 bottle pairs from 62 patients were determined as compliant. Two isolates were recovered from compliant positive bottle pairs with one isolate recovered on VIRTUO and another isolate recovered on BTA 3D. A total of 159 compliant bottle pairs were negative on both VIRTUO and BTA 3D.
One false positive PF Plus Culture Bottle was observed on VIRTUO (1/161, 0.62%). No false positive PF Plus Culture Bottles were observed on BTA 3D.
Terminal subcultures were performed for 50 PF Plus bottle pairs that were negative on both VIRTUO and BTA 3D and no false negative results were observed for VIRTUO or
32
{32}
BTA 3D.
Table 32 compares true positive results of compliant PF Plus blood cultures incubated on VIRTUO and BTA 3D that yielded any number of isolates on subculture.
Table 32: PF Plus - Blood - Compliant – Single and Multiple Isolates Combined
| Clinical Determination | VIRTUO True Positives | % of VIRTUO True Positives in Population | BTA3D True Positives | % of BTA3D True Positives in Population | Ratio of True Positives (VIRTUO /BTA3D) | 95% CI (LCL, UCL) |
| --- | --- | --- | --- | --- | --- | --- |
| Significant | 1 | 0.6 (1/161) | 1 | 0.6 (1/161) | 1.000 | -1.772, 3.772* |
| Contaminant | 0 | 0.0 (0/161) | 0 | 0.0 (0/161) | - | ** |
| Unknown | 0 | 0.0 (0/161) | 0 | 0.0 (0/161) | - | ** |
| Total | 1 | 0.6 (1/161) | 1 | 0.6 (1/161) | 1.000 | -1.772, 3.772* |
*not statistically relevant due to the small sample size
** Confidence intervals not calculated due to small sample size.
### Section M.2.I.d- Low-Fill FA Plus Bottles (Surrogate for PF Plus bottles) Clinical Performance:
PF Plus bottles contain the same media composition as FA Plus bottles with the only difference being the required blood volume described in labeling and use in the clinical setting. Due to the low numbers of positive PF Plus bottles observed in the clinical study and in order to further compare the performance of VIRTUO and BTA 3D instruments for low volumes that would typically be collected from pediatric patients using PF Plus Culture Bottles, an evaluation was performed with low-fill FA Plus Culture Bottles (from adult patients) inoculated with blood volumes of ≤4 mL.
A total of 550 FA Plus bottle pairs with <4 mL blood fill volumes were tested on VIRTUO and BTA 3D. Of these, 379 bottle pairs from 292 adult patients had compliant fill volumes. A total of 40 isolates were recovered from all compliant low-fill FA Plus blood culture pairs with a positive status. A total of 33 isolates were recovered from low-fill FA Plus Culture Bottles on VIRTUO and 32 isolates were recovered from low-fill FA Plus Culture Bottles on BTA 3D. Of the significant isolates, the VIRTUO FA Plus Culture Bottle detected a total of 28 isolates compared to the BTA 3D Culture Bottle which detected 29 isolates.
No false positive low-fill FA Plus bottles were observed for VIRTUO or BTA 3D.
Terminal subcultures were performed for 246 low-fill FA Plus bottle pairs that were negative on both VIRTUO and BTA 3D. No false negative results were observed for bottles incubated on either instrument.
33
{33}
Table 33 compares results for VIRTUO and BTA 3D for all compliant low-fill FA Plus blood culture bottle pairs. No compliant low-fill FA Plus bottle pairs with a positive status yielded multiple isolates on subculture.
Table 33 Low Fill FA Plus - Blood – Compliant –Single Isolates
| Clinical Determination | VIRTUO True Positives | % of VIRTUO True Positives in Population | BTA3D True Positives | % of BTA3D True Positives in Population | Ratio of True Positives (VIRTUO /BTA3D) | 95% CI (LCL, UCL) |
| --- | --- | --- | --- | --- | --- | --- |
| Significant | 28 | 7.4 (28/379) | 29 | 7.7 (29/379) | 0.966 | 0.790, 1.142 |
| Contaminant | 4 | 1.1 (4/379) | 3 | 0.8 (3/379) | 1.333 | * |
| Unknown | 1 | 0.3 (1/379) | 0 | 0.0 (0/379) | - | * |
| Total | 33 | 8.7 (33/379) | 32 | 8.4 (32/379) | 1.031 | 0.790, 1.272 |
* Confidence intervals not calculated due to small sample size.
Table 34 includes the comparative yield of microorganisms (number of isolates) recovered on subculture from compliant Low Fill FA Plus culture bottles.
Table 34. Low Fill FA Plus - Comparative Yield of Microorganisms (Number of Isolates)
| Group | BacT/ALERT VIRTUO | BacT/ALERT 3D |
| --- | --- | --- |
| Enterobacteriaceae | 8 | 9 |
| Enterococcus spp. | 3 | 2 |
| Yeasts | 2 | 1 |
| Non-fermentative Gram-Negative Bacilli | 2 | 1 |
| Other Gram-Positive | 0 | 1 |
| Coagulase-Negative Staphylococcus | 5 | 5 |
| Staphylococcus aureus | 6 | 7 |
| Streptococcus spp. | 6 | 5 |
| Other | 1 | 1 |
| All | 33 | 32 |
NOTE: Isolate table includes polymicrobic cultures.
### Section M.2.1.e- SA Bottles (Blood) Clinical Performance:
A total of 1046 SA bottle pairs, obtained from 508 adult patients suspected of blood stream bacterial/yeast infections were tested on both VIRTUO and BTA 3D instruments. Of these, 776 bottle pairs from 440 adult patients were determined to be compliant.
A total of 60 isolates were recovered by subculture from all compliant SA Culture Bottle pairs with a positive status. At least one isolate was recovered from a total of 56 bottle pairs with a single isolate recovered from 52 bottle pairs and two isolates recovered from four bottle pairs.
A total of 46 isolates were recovered from SA Culture Bottles on VIRTUO and a total of
34
{34}
50 isolates were recovered from SA Culture Bottles on BTA 3D. Of the significant isolates, the VIRTUO SA Culture Bottles detected a total of 40 isolates compared to the BTA 3D SA Culture Bottles which detected 39 isolates.
Two false positive SA Culture Bottles were observed on VIRTUO (2/780, 0.26%) and three false positive SA Bottles were observed on BTA 3D (3/780, 0.38%).
Terminal subcultures were performed for 779 SA Culture Bottle pairs that were negative on both VIRTUO and BTA 3D. Five false negative bottles were observed for FN Plus Culture Bottles on both VIRTUO and BTA 3D. For negative bottle pairs that were subcultured, the final false negative rate was 0.64% (5/779) for both instruments.
The following tables compare results of true positive blood cultures incubated on VIRTUO and BTA 3D for all compliant SA Culture Bottles yielding any number of isolates on subculture (Table 35), a single isolate on subculture (Table 36), and multiple isolates on subculture (Table 37).
**Table 35. SA Bottles - Blood Culture – Compliant – Single and Multiple Isolates**
| Clinical Determination | VIRTUO True Positives | % of VIRTUO True Positives in Population | BTA3D True Positives | % of BTA3D True Positives in Population | Ratio of True Positives (VIRTUO/BTA3D) | 95% CI (LCL, UCL) |
| --- | --- | --- | --- | --- | --- | --- |
| Significant | 40 | 5.1 (40/780) | 39 | 5.0 (39/780) | 1.026 | 0.857, 1.195 |
| Contaminant | 4 | 0.5 (4/780) | 10 | 1.3 (10/780) | 0.400 | * |
| Unknown | 2 | 0.3 (2/780) | 1 | 0.1 (1/780) | 2.000 | * |
| Total | 46 | 5.9 (46/780) | 50 | 6.4 (50/780) | 0.920 | 0.736, 1.104 |
\* Confidence intervals not calculated due to small sample size.
**Table 36. SA Bottles– Blood Culture– Compliant - Single Isolates**
| Clinical Determination | VIRTUO True Positives | % of VIRTUO True Positives in Population | BTA3D True Positives | % of BTA3D True Positives in Population | Ratio of True Positives (VIRTUO/BTA3D) | 95% CI (LCL, UCL) |
| --- | --- | --- | --- | --- | --- | --- |
| Significant | 33 | 4.3 (33/772) | 32 | 4.1 (32/772) | 1.031 | 0.825, 1.237 |
| Contaminant | 4 | 0.5 (4/772) | 10 | 1.3 (10/772) | 0.400 | * |
| Unknown | 1 | 0.1 (1/772) | 0 | 0.0 (0/772) | - | * |
| Total | 38 | 4.9 (38/772) | 42 | 5.4 (42/772) | 0.905 | 0.688, 1.122 |
\* Confidence intervals not calculated due to small sample size.
35
{35}
Table 37. SA Bottles – Blood Culture – Compliant - Multiple Isolates
| Clinical Determination | VIRTUO True Positives | % of VIRTUO True Positives in Population | BTA3D True Positives | % of BTA3D True Positives in Population | Ratio of True Positives (VIRTUO/BTA3D) | 95% CI (LCL, UCL) |
| --- | --- | --- | --- | --- | --- | --- |
| Significant | 7 | 87.5 (7/8) | 7 | 87.5 (7/8) | 1.000 | 1.000, 1.000 |
| Contaminant | 0 | 0.0 (0/8) | 0 | 0.0 (0/8) | - | * |
| Unknown | 1 | 12.5 (1/8) | 1 | 12.5 (1/8) | 1.000 | * |
| Total | 8 | 100.0 (8/8) | 8 | 100.0 (8/8) | 1.000 | 1.000, 1.000 |
* Confidence intervals not calculated due to small sample size.
Table 38 includes the comparative yield of microorganisms (number of isolates) recovered on subculture from compliant SA Culture Bottles.
Table 38. SA Bottles - Comparative Yield of Microorganisms From VIRTUO…
