Real-time PCR法を用いた血液培養からのMRSA迅速診断法の検討

Abstract

Methicillin-resistant Staphylococcus aureus (MRSA), a well-known causative multidrug-resistant pathogen responsible for nosocomial and community-acquired infections, particularly in blood stream infection, often proves difficult and expensive to treat. Despite the need for rapid, accurate MRSA detection for treatment and infection control, conventional testing including culture, have sensitivity and turn-around time (TAT) problems. We evaluated BD GeneOhm MRSA Detection Kit rapid detection performance directly from positive blood culture using real-time PCR. The kit recognizes, a specific part of the staphylococcal cassette chromosome mec (SCCmec) gene, not a mecA gene. Compared to conventional culture in 138 samples with gram stains showing gram-positive cocci (GPC) clusters, the kit's sensitivity was 100%, specificity 97.3%, positive predictive value 90% and negative predictive value 100%. Three of the 27 MSSA isolates found was false-positive, indicating that the kit detected SCCmec/orfX region sequences lacking mecA. Coupled with direct tube coagulase testing to rapidly differentiate MRSA from methicillin-susceptible S. aureus (MSSA) could provide optimum treatment through appropriate antibiotic use. The kit thus appears to be useful in rapidly diagnosing MRSA from blood culture, improving the prognosis and reducing medical cost.