Accuracy of cefoxitin in detection of oxacillin resistance mediated by PBP2a in coagulase-negative staphylococci

BEATRIZ PERAZZI; MARCELO RODRIGUEZ FERMEPIN; ALICIA MALIMOVKA; SUSANA GARCÍA; MAURICIO ORGAMBIDE; CARLOS VAY; RAMÓN DE TORRES; ANGELA FAMIGLIETTI

JOURNAL OF CLINICAL MICROBIOLOGY

Publicación Oficial de la Sociedad Americana de Microbiología.

Lugar: Washington DC; Año: 2006 vol. 44 p. 3634 - 3639

0095-1137

The Clinical and Laboratory Standards Institute (CLSI) proposed, beginning in 2004, the use of cefoxitindisks to predict resistance mediated by the mecA gene in all species of coagulase-negative staphylococci(CoNS). The aim of this work was to evaluate the efficiency of the cefoxitin disk and of oxacillin-salt agarscreening (MHOX) to characterize the oxacillin resistance mediated by the mecA gene in CoNS. One hundredseven CoNS isolates from different clinical samples were studied. Detection of the mecA gene by PCR wasconsidered the ?gold standard.? The susceptibility to oxacillin and cefoxitin was detected by the disk diffusionand agar dilution tests, as described by the CLSI. MHOX was also performed with 6 g/ml of oxacillin and 4%NaCl. The sensitivities of the oxacillin and cefoxitin disks for all CoNS species were 88% and 80%, respectively,whereas the specificities were 63% and 100%, respectively. The sensitivities of the agar dilution test for oxacillinand cefoxitin (for proposed breakpoints of >4 g/ml for resistance and