title: Evaluation of oxacillin and cefoxitin disks for detection of resistance in coagulase negative staphylococci.
abstract: Coagulase-negative Staphylococcus spp. was considered nonpathogenic until the emergence of multiresistance and the demonstration of their participation as infectious agents. In Brazil, oxacillin resistance may be present in over 80% of isolates, and the Clinical and Laboratory Standards Institute standardized a disk-diffusion method to predict this resistance in Staphylococcus. The aim of this study was to evaluate the variability among commercial disks of oxacillin (1 microg) and cefoxitin (30 microg) widely used in clinical laboratories of microbiology, compared with mecA gene and minimum inhibitory concentration (MIC) of oxacillin. The use of oxacillin and cefoxitin disks simultaneously allowed the detection of important differences, particularly, in less frequent species such as S. cohnii, S. haemolyticus, S. saprophyticus, and S. sciuri. Disks of cefoxitin of the brand 2 displayed good correlation with the mecA gene (98.7%) and oxacillin MIC (97.8%), while major discrepancies were observed using disks of brand 1. One of the critical points in the diffusion disk test is the quality of the disks: the use of better quality disks associated with molecular methods lead to better results to define the best antibiotic therapy.
authors.affiliation: Faculdade de Farmácia, Universidade Federal do Rio Grande do Sul, Porto Alegre, RS, 90610-000, Brasil.
authors.forename: Ana Lúcia
authors.initials: AL
authors.lastname: Souza Antunes
authors.forename: Carina
authors.initials: C
authors.lastname: Secchi
authors.forename: Keli Cristine
authors.initials: KC
authors.lastname: Reiter
authors.forename: Leandro Reus
authors.initials: LR
authors.lastname: Rodrigues Perez
authors.forename: Ana Lúcia
authors.initials: AL
authors.lastname: Peixoto de Freitas
authors.forename: Pedro
authors.initials: P
authors.lastname: Alves d'Azevedo
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D001426:Bacterial Proteins / Q000235:genetics; D002440:Cefoxitin / Q000494:pharmacology*; D003030:Coagulase; D006801:Humans; D016106:Methicillin Resistance / Q000235:genetics*; D008826:Microbial Sensitivity Tests; D010068:Oxacillin / Q000494:pharmacology*; D046915:Penicillin-Binding Proteins; D012680:Sensitivity and Specificity; D013210:Staphylococcus / Q000187:drug effects* / Q000201:enzymology / Q000235:genetics
chemical_list: D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins; D003030:Coagulase; D046915:Penicillin-Binding Proteins; C487789:mecA protein, Staphylococcus aureus; D002440:Cefoxitin; D010068:Oxacillin