Rapid Identification ofStaphylococcus aureus: FISH Versus PCR Methods

Abstract

Background: Staphylococcus aureus (S aureus) is the most important pathogen in the genus Staphylococcus. The ability to rapidly and accurately distinguish between S aureus and non–S aureus bacteria (coagulase-negative Staphylococcus species [CoNS]) is essential for the appropriate therapeutic use of antibiotics and timely intervention for infection control. Several methods have been reported as being effective in the rapid identification of S aureus, among which molecular biological methods have the most potential. Methods: In this study, 2 molecular techniques, fluorescence in situ hybridization (FISH) and polymerase chain reaction (PCR), were compared in 1300 clinical specimens. After smear testing, specimens containing gram-positive cocci in clusters were submitted for investigation. These specimens had been subjected to FISH analysis and PCR examination. Overall, we gathered statistics on 131 specimens that had been determined to be members of the Staphylococcus genus. We compared the effectiveness, efficiency, and costliness of the 2 methods. Results: Comparing the culture determination methods revealed that the identification sensitivity, specificity, and positive and negative predictive values were 100%, 100%, 100% and 100%, respectively, for the FISH method and 98.5%, 100%, 100% and 98.5%, respectively, for the PCR method. The FISH method took approximately 3 hours to complete per sample, whereas PCR took approximately 4 hours. S aureus was differentiated from CoNS via the FISH method 1 hour faster than via PCR identification. Conclusion: Although the FISH and PCR methods both allow for the rapid and reliable identification of S aureus in clinical specimens, FISH is more appropriate for testing a few specimens, whereas PCR is more appropriate for testing a large number of specimens at a lower cost.