S. AUREUS PNA FISH

K091827 · Advandx, Inc. · NXX · Aug 18, 2009 · Microbiology

Device Facts

• Record ID: K091827
• Device Name: S. AUREUS PNA FISH
• Applicant: Advandx, Inc.
• Product Code: NXX · Microbiology
• Decision Date: Aug 18, 2009
• Decision: SESE
• Submission Type: Traditional
• Regulation: 21 CFR 866.3700
• Device Class: Class 1

Indications for Use

S. aureus PNA FISH is a qualitative nucleic acid hybridization assay intended for the identification of S. aureus on smears made from positive blood cultures containing Gram-positive cocci in clusters observed on Gram stain. Subculturing of positive blood cultures is necessary for susceptibility testing and/or differentiation of mixed growth. S. aureus PNA FISH is intended as an aid in the diagnosis of S. aureus bacteremia.

Device Story

In vitro diagnostic assay; utilizes peptide nucleic acid (PNA) fluorescence in situ hybridization (FISH) technology. Input: smears prepared from positive blood cultures containing Gram-positive cocci in clusters. Process: PNA probes hybridize to specific ribosomal RNA sequences within the organism; fluorescently labeled probes allow visualization. Output: fluorescent signal indicating presence or absence of S. aureus. Used in clinical microbiology laboratories by trained technicians. Results aid clinicians in rapid identification of S. aureus bacteremia, facilitating targeted antimicrobial therapy and potentially improving patient outcomes by reducing time to appropriate treatment.

Clinical Evidence

No clinical data provided in the summary document; substantial equivalence based on technological characteristics and performance comparison to predicate.

Technological Characteristics

Nucleic acid hybridization assay using PNA probes. Fluorescence microscopy detection. Qualitative result. Standalone diagnostic kit.

Indications for Use

Indicated for identification of Staphylococcus aureus in patients with positive blood cultures showing Gram-positive cocci in clusters on Gram stain. Used as an aid in diagnosing S. aureus bacteremia. Requires subculturing for susceptibility testing.

Regulatory Classification

Identification

Staphylococcus aureus serological reagents are devices that consist of antigens and antisera used in serological tests to identify enterotoxin (toxin affecting the intestine) producing staphylococci from cultured isolates. The identification aids in the diagnosis of disease caused by this bacterium belonging to the genus Staphylococcus and provides epidemiological information on these diseases. Certain strains of Staphylococcus aureus produce an enterotoxin while growing in meat, dairy, or bakery products. After ingestion, this enterotoxin is absorbed in the gut and causes destruction of the intestinal lining (gastroenteritis).

Predicate Devices

• S. aureus PNA FISH (K060099)

Submission Summary (Full Text)

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510(k) SUBSTANTIAL EQUIVALENCE DETERMINATION
DECISION SUMMARY
ASSAY ONLY TEMPLATE

A. 510(k) Number:
K091827

B. Purpose for Submission:
To obtain a SE determination for a modification of the assay procedure for S. aureus PNA FISH. The specific modifications are: elimination of the 5-10 minutes ethanol step in smear preparation; a reduction of the hybridization time from 90 minutes to 30 minutes

C. Measurand:
S. aureus specific ribosomal RNA sequences

D. Type of Test:
Fluorescence In Situ Hybridization (FISH) using protein nucleic acid (PNA) probes

E. Applicant:
AdvanDx, Inc

F. Proprietary and Established Names:
AdvanDx S. aureus PNA FISH Culture Identification Kit

G. Regulatory Information:
1. Regulation section:
866.3700
2. Classification:
Class I
3. Product code:
NXX

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4. Panel:

83 Microbiology

H. Intended Use:

1. Intended use(s):

S. aureus PNA FISH is a qualitative nucleic acid hybridization assay intended for the identification of S. aureus on smears made from positive blood cultures containing Gram-positive cocci in clusters observed on Gram stain. Subculturing of positive blood cultures is necessary for susceptibility testing and/or differentiation of mixed growth.

S. aureus PNA FISH is intended as an aid in the diagnosis of S. aureus bacteremia.

2. Indication(s) for use:

S. aureus PNA FISH is a qualitative nucleic acid hybridization assay intended for the identification of S. aureus on smears made from positive blood cultures containing Gram-positive cocci in clusters observed on Gram stain. Subculturing of positive blood cultures is necessary for susceptibility testing and/or differentiation of mixed growth.

S. aureus PNA FISH is intended as an aid in the diagnosis of S. aureus bacteremia.

3. Special conditions for use statement(s):

Prescription use only

4. Special instrument requirements:

Dual Band Filter (Cat. No. AC003)

Microscope Slides (Cat. No. AC001)

I. Device Description:

The S. aureus PNA FISH is a fluorescence *in situ* hybridization (FISH) method using PNA probes hybridizing to S. aureus-specific ribosomal RNA (rRNA) sequences to detect S. aureus. PNA FISH is performed directly on smears fixed onto microscope slides. The fluorescein-labeled PNA probes are added to a smear prepared from a positive blood culture. Hybridization is performed at 55°C for 30 minutes. The hybridization is followed by a post-hybridization wash at 55°C for 30 min with a stringent Wash Solution to remove unbound PNA probe. Finally, the smear is

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mounted with Mounting Medium and examined by fluorescence microscopy.

## J. Substantial Equivalence Information:

1. Predicate device name(s):

*S. aureus* PNA FISH

2. Predicate 510(k) number(s):

K060099

3. Comparison with predicate:

| Similarities | | |
| --- | --- | --- |
| Item | Device | Predicate |
| Technology | Fluorescence In Situ Hybridization (FISH) using protein nucleic acid (PNA) probe | Same |
| Sample | Positive blood culture | Same |
| PNA Probes | Fluorescein-labeled S. aureus specific PNA probe | Same |
| Differences | | |
| --- | --- | --- |
| Item | Device | Predicate |
| Fixed smear treatment | None | Ethanol for 10 minutes and air dried |
| Hybridization at 55°C | 30 minutes | 90 minutes |

## K. Standard/Guidance Document Referenced (if applicable):

Non applicable

## L. Test Principle:

The PNA FISH technology uses species-specific peptide nucleic acid (PNA) probes in a fluorescence *in situ* hybridization format. rRNA sequencing is able to detect differences between closely related species. Each microorganism harbors several thousand rRNA molecules in sufficient concentration to allow individual cells to be detected and identified by fluorescent-labeled probes. The fluorescein-labeled PNA probes are added to a smear prepared from a blood culture. Hybridization is performed at 55°C for 30 minutes. The hybridization is followed by a post-hybridization wash at 55°C for 30 min with a stringent Wash Solution. Finally, the smear is mounted with Mounting Medium and examined by fluorescence microscopy.

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M. Performance Characteristics (if/when applicable):

1. Analytical performance:

a. Precision/Reproducibility:

A reproducibility study for *S. aureus* PNA FISH assay was performed by using ten reference Gram positive cocci, in triplicates with positive and negative controls, over a period of three days at three different sites, by at least two different operators at each site. Results showed 100% precision and reproducibility between and within sites.

b. Linearity/assay reportable range:

Not applicable

c. Traceability, Stability, Expected values (controls, calibrators, or methods):

Positive and negative control slides were performed at each testing site on each day of testing. All results were as expected.

d. Detection limit:

The detection limit was determined to be approximately 10⁵ CFU/mL by serial dilutions of *S. aureus* cultures. The average number of colonies per mL (CFU/mL) was calculated from three plates. The data sets showed a minimum of 10⁵ CFU/mL to produce a positive result for the *S. aureus* PNA FISH™ assay.

e. Analytical specificity:

The modified assay procedure was tested and compared to the original assay procedure. *S. aureus* PNA FISH was evaluated on (46) *S. aureus*, (66) other additional Gram positive organisms (i.e. 42 *Staphylococcus* spp); (32) Gram negative organisms, and (5) yeasts representing phylogenetically closely related organisms and a variety of clinically significant organisms. All (46) *S. aureus* showed green fluorescence in both procedures; (2) *S. schleiferi* showed weak positive results and all other (100) organisms were negative.

f. Assay cut-off:

Not applicable

2. Comparison studies:

a. Method comparison of device to conventional methods, as the reference method:

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The modified assay procedure was compared to the original assay procedure and the conventional culture methods.

# b. Matrix comparison:

Not applicable

# 3. Clinical studies:

The Clinical Study was conducted at three sites: the performance of S. aureus PNA FISH (New) was compared to S. aureus PNA FISH, and to conventional routine methods. A total of 208 blood culture bottles with Gram positive cocci in clusters (GPCC) were included in the studies.

Performance results of the modified, shortened assay procedure (i.e. 30 minutes hybridization, prepared smears not treated with ethanol) compared to the original assay procedure, and compared to the conventional methods are summarized below.

Performance Data for S. aureus PNA FISH (Shortened) vs. S. aureus PNA FISH (Original)

| Study | Positive Agreement | Negative Agreement | Blood Culture System |
| --- | --- | --- | --- |
| A | 100% (15/15) | 100% (35/35) | BacT/ALERT |
| | 95% CI (81.9-100) | 95% CI (91.8-100) | |
| B | 96.9% (32/33) | 100% (70/70) | VersaTREK |
| | 95% CI (84.2-99.9) | 95% CI (95.8-100) | |
| C | 100% (13/13) | 100% (42/42) | BACTEC |
| | 95% CI (79.4-100) | 95% CI (93.1-100) | |
| Total | 98.4% (60/61) | 100% (147/147) | |
| | 95% CI (91.2-100) | 95% CI (98.0-100) | |

Performance Data for S. aureus PNA FISH (New) vs. Conventional Methods

| Study | Sensitivity | Specificity | Blood Culture System |
| --- | --- | --- | --- |
| A | 100% (15/15) | 100% (35/35) | BacT/ALERT |
| | 95% CI (81.9-100) | 95% CI (91.8-100) | |
| B | 100% (32/32) | 100% (71/71) | VersaTREK |
| | 95% CI (84.2-99.9) | 95% CI (95.8-100) | |
| C | 100% (13/13) | 100% (42/42) | BACTEC |
| | 95% CI (79.4-100) | 95% CI (93.1-100) | |
| Total | 100% (60/60) | 100% (148/148) | |
| | 95% CI (95.1-100) | 95% CI (98-100) | |

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a. Clinical Sensitivity:
Not applicable

b. Clinical specificity:
Not applicable

c. Other clinical supportive data (when a. and b. are not applicable):
Not applicable

4. Clinical cut-off:
Not applicable

5. Expected values/Reference range:
S. aureus cells: bright green fluorescent cocci in multiple fields
The expected positive rate from positive blood culture bottles is 30%-43% for S. aureus

N. Proposed Labeling:
The labeling is sufficient and it satisfies the requirements of 21 CFR Part 809.10.

O. Conclusion:
The information submitted in this premarket notification is complete and supports a substantial equivalence decision.