Evaluation of Hemofast MRSA for identification of Staphylococcus aureus and detection of methicillin-resistance staphylococci, directly in blood culture broths
Langlet, S.; Scheftel, J.M.; Monteil, H.; Ghnassia, J.C.
Pathologie-Biologie 47(5): 497-500
1999
ISSN/ISBN: 0369-8114 PMID: 10418027 Document Number: 507517
The newly developed Hemofast MRSA system for Staphylococcus aureus identification and methicillin-resistant staphylococci (MRS) detection in blood culture broths was evaluated in 106 Bactec broths containing grapelike clusters of Gram-positive cocci. All 26 S. aureus positive broths were correctly identified by Hemofast MRSA within two hours, and 81% were identified within one hour. Sensitivity and specificity were both 100%. Accuracy of MRS detection was 100%, i.e., no discrepancies versus the agar diffusion method were found. When the 28 broths containing coagulase negative staphylococci (CNS) were tested using an inoculum ten fold larger than for S. aureus testing, a number of discrepancy were recorded. For 49 other broths containing CNS, accuracy was 98.5% when the test was interpreted based on the growth rate of the strain, according to the manufacturer's instructions. One broth containing S. epidermidis strain susceptible yielded a false result with Hemofast MRSA, indicating that it probably contained a contaminant. The other discrepancies occurred with specimens containing mixed populations with CNS or a Micrococcus strain. Most (85%) results were available within 4 hrs 30 min, irrespective of the S. aureus or CNS strains. Avoiding the isolation step on agar, Hemofast MRSA saves 24 to 48 hours, thus allowing earlier antistaphylococcal treatment.