Evaluation of the accuracy of various phenotypic tests to detect oxacillin resistance in coagulase-negative staphylococci.
In this study, we determined the accuracy of phenotypic tests (cefoxitin agar dilution, 30 microg-cefoxitin and 1 microg-oxacillin disks) to detect the oxacillin resistance/mecA gene among coagulase-negative staphylococci (CoNS) isolates. The presence of the mecA gene was detected by PCR technique (gold standard). A total of 176 CoNS isolates from blood of hospitalized patients were evaluated. Of these, 138 (78.4%) harbored the mecA gene. Using 30 microg-cefoxitin and 1 microg-oxacillin disks we obtained 100 and 98.3% accuracy, respectively. In addition, when cefoxitin was used as marker in an agar dilution method, the higher accuracy (99.4%) was established with 8 mg cefoxitin per mL breakpoint. Thus, despite of the agar dilution method using cefoxitin as a marker not being standard for this detection, our results suggested that it is an excellent alternative to detect the oxacillin resistance/mecA gene among CoNS isolates.
Perez
Leandro Reus Rodrigues
LR
Microbiology Unit, Mãe de Deus Hospital, 2Postgraduate Program in Pharmaceutical Sciences, Federal University of Rio Grande do Sul, PortoAlegre, RS, Brazil. leandro.reus@gmail.com
d'Azevedo
Pedro Alves
PA
D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D001426:Bacterial Proteins / Q000235:genetics*; D002440:Cefoxitin / Q000494:pharmacology*; D052978:Disk Diffusion Antimicrobial Tests / Q000379:methods; D006801:Humans; D016106:Methicillin Resistance / Q000235:genetics*; D010068:Oxacillin / Q000494:pharmacology*; D046915:Penicillin-Binding Proteins; D010641:Phenotype; D011237:Predictive Value of Tests; D012372:ROC Curve; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013210:Staphylococcus / Q000187:drug effects* / Q000235:genetics
D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins; D046915:Penicillin-Binding Proteins; C487789:mecA protein, Staphylococcus aureus; D002440:Cefoxitin; D010068:Oxacillin