Identification of mecA-related oxacillin resistance in staphylococci by the E test and the broth microdilution method

The Journal of Antimicrobial Chemotherapy
A C PeterssonC Kamme

Abstract

A set of 165 strains of different staphylococcal species, 67 Staphylococcus aureus, 71 novobiocin-sensitive coagulase-negative staphylococci (CNS) and 27 novobiocin-resistant CNS was used. The oxacillin and methicillin MICs were recorded after 24 and 42 h of incubation at 35 degrees C and at 30 degrees C. Significantly higher MICs were recorded at 30 degrees C compared with 35 degrees C. While a poor discrimination between mecA-positive and mecA-negative strains was obtained with methicillin, the oxacillin MICs enabled identification of resistant strains under certain conditions. The distribution of MICs differed between the three groups of species. Separation of uninduced mecA-positive (> or = 4.0 mg oxacillin/L) and mecA-negative (< or = 2.0 mg oxacillin/L) strains of S. aureus was only achieved with the E test and after 42 h of incubation. Oxacillin-induction yielded higher MICs for mecA-positive strains of S. aureus, and a separation from mecA-negative strains was achieved with the E test after 24 h and with the broth microdilution method after 42 h. Separation of mecA-positive and mecA-negative strains of novobiocin-sensitive CNS required agar supplemented with 5% blood, incubation of MIC trays and E test for 42 h, and spe...Continue Reading

Citations

Jul 1, 1996·Diagnostic Microbiology and Infectious Disease·M G CormicanR N Jones
Jun 4, 1999·Diagnostic Microbiology and Infectious Disease·F BekkaouiR N Bryan
Oct 8, 1999·The Journal of Antimicrobial Chemotherapy·M De GiustiC Chiesa
Nov 19, 2005·The Journal of Antimicrobial Chemotherapy·Derek F J BrownUNKNOWN Infection Control Nurses Association
Jun 3, 2006·Archives of Pathology & Laboratory Medicine·Michael A PfallerUNKNOWN Microbiology Resource Committee, College of American Pathologists

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