ABSTRACT
Eight Staphylococcus aureus strains initially identified by Vitek GPS-BS or GPS-SA cards as resistant to oxacillin, but susceptible to most non-beta-lactam antibiotics, were found on further testing to be susceptible to oxacillin and ceftizoxime by disk diffusion tests. For all these strains, the MICs of oxacillin were =0.5 microg/ml by agar dilution tests, and the strains were oxacillin susceptible when tested by the BBL Crystal MRSA ID and a Vitek machine with GPS-101 cards. None grew on oxacillin-salt agar screening plates. None were positive for mecA gene sequences by PCR. When S. aureus strains tested by Vitek GPS-SA or GPS-BS cards appear resistant to only penicillin and oxacillin, a confirmatory test such as the oxacillin-salt agar screening method should be performed.
Subject(s)
Methicillin Resistance , Microbial Sensitivity Tests/methods , Staphylococcus aureus/drug effects , Oxacillin/pharmacologyABSTRACT
The RapID Yeast Plus system (Innovative Diagnostic Systems, Norcross, Ga.) is a qualitative micromethod employing conventional tests and single-substrate chromogenic tests and having a 4-h incubation period. This system was compared with the API20C (bioMerieux Vitek, Hazelwood, Mo.) system, a 24- to 72-h carbohydrate assimilation method. One hundred thirty-three clinical yeast isolates, including 57 of Candida albicans, 26 of Candida tropicalis, 23 of Candida glabrata, and 27 of other yeasts, were tested by both methods. When discrepancies occurred, isolates were further tested by the Automated Yeast Biochemical Card (bioMerieux Vitek). Germ tube production and microscopic morphology were used as needed to definitively identify yeast isolates. The RapID Yeast Plus system correctly identified 125 yeast isolates, with an overall accuracy of 94% (125 of 133). Excellent correlation was found in the recognition of the three yeasts most commonly isolated from human sources. The test was 99% (105 of 106 isolates) accurate with C. albicans, C. tropicalis, and C. glabrata. The RapID Yeast Plus system compares favorably with the API20C system and provides a simple, accurate alternative to conventional assimilation methods for the rapid identification of the most commonly encountered isolates of Candida species.