An Evaluation of the AdvanDx Staphylococcus aureus/CNS PNA FISH™ Assay

Donna M Hensley; Rachel Tapia; Yadira Encina

doi:10.29074/ascls.22.1.30

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Donna M Hensley, MT(ASCP)⇑
1. is research medical technologist; of 59th Medical Wing, Lackland AFB TX
Rachel Tapia, MLT(ASCP)
1. is microbiology medical technologist; of 59th Medical Wing, Lackland AFB TX
Yadira Encina, MT(ASCP)
1. is microbiology technical supervisor; of 59th Medical Wing, Lackland AFB TX

Address for correspondence: Donna M Hensley MT(ASCP), research medical technologist, 59^th MDW/SGVUL, 59^th Clinical Research Division, 2200 Bergquist Dr., Bldg 4430, Lackland AFB TX 78236-9908. (210) 292-6690, (210) 292-6053 (fax). donna.hensley{at}lackland.af.mil.

Abstract

PURPOSE: A study was conducted to compare the S. aureus/CNS PNA FISH™ Culture Identification Kit (AdvanDx, Woburn MA) to standard microbiology identification methods for presumptive identification of S. aureus and coagulase-negative staphylococcus (CNS) in positive blood cultures.

MATERIALS AND METHODS: Blood cultures (n=301) that signaled positive on the BacT/Alert™ 3D (bioMerieux, Durham NC) automated blood culture system and had gram-positive cocci in clusters on Gram stain were processed using standard microbiology methods and were analyzed with the S. aureus/CNS PNA FISH™ assay. The S. aureus/CNS PNA FISH™ assay was performed in accordance with the manufacturer's instructions.

RESULTS: Overall agreement was 96.7%. Sensitivity for S. aureus was 96.5% (83/86). Specificity for S. aureus was 100% (215/215). Sensitivity for CNS was 96.6% (201/208). Specificity for CNS was 96.8% (90/93). Three cultures reported as S. aureus were identified as CNS by S. aureus/CNS PNA FISH™. Three cultures that reported only S. aureus were positive for both S. aureus and CNS by S. aureus/CNS PNA FISH™. One S. viridans was identified as CNS by S. aureus/CNS PNA FISH™. Seven cultures that reported CNS were negative by S. aureus/CNS PNA FISH™.

CONCLUSION: When used in conjunction with Gram stain and culture the S.aureus/CNS PNA FISH™ assay may be beneficial in terms of reducing time to correct therapy, thereby decreasing mortality and costs associated with S. aureus bacteremia.

ABBREVIATIONS: CNS = coagulase negative staphylococci; FISH = fluorescent in situ hybridization; PNA = peptide nucleic acid.