title: Evaluation of the accuracy of various phenotypic tests to detect oxacillin resistance in coagulase-negative staphylococci.
abstract: 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.
authors.affiliation: 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
authors.forename: Leandro Reus Rodrigues
authors.initials: LR
authors.lastname: Perez
authors.forename: Pedro Alves
authors.initials: PA
authors.lastname: d'Azevedo
mesh_terms: 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
chemical_list: D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins; D046915:Penicillin-Binding Proteins; C487789:mecA protein, Staphylococcus aureus; D002440:Cefoxitin; D010068:Oxacillin