Evaluation of accuracy and cost of four different methods for
detection of methicillin resistance in Staphylococcus
aureus isolates from pediatric patients hospitalized in Brazil
Affiliations: Department of Pediatrics, Santa Casa University
Hospital, Sao Paulo, SP, Brazil | Department of Pathology, Santa Casa University
Hospital , Sao Paulo, SP, Brazil | Laboratory of Medical Investigation, LIM 03, Hospital
das Clinicas-FMUSP, Sao Paulo, SP, Brazil
Note: [] Correspondence: Marcelo Jenne Mimica, M.D., Rua Doutor
Cesário Motta Júnior, 112, Departamento de Pediatria, Santa Casa de Sao
Paulo. Santa Cecília 01221-020, Sao Paulo, SP, Brazil. Tel.: +55 11
81752258; Fax: +55 11 3361 7333; E-mail: [email protected]
Abstract: We studied 70 pediatric clinical isolates of Staphylococcus
aureus to perform a comparison of different methods for detection of
methicillin-resistant S. aureus (MRSA) using polymerase chain reaction
for mecA as the "gold standard" assay. The isolates were tested with
oxacillin and cefoxitin discs, oxacillin agar screening plate and E-test. Of
the 70 strains, 43 were mecA-positive and 27 mecA-negative.
Oxacillin agar screening plate and E-test had 100% sensitivity and
specificity for the presence of mecA gene. We found a specificity of
96% for both disc-diffusion methods, and sensitivities of 95% (oxacillin
disc) and 93% (cefoxitin disc). However, with the new Clinical and
Laboratory Standards Institute 2007 cefoxitin breakpoints the sensitivity of
this method would be increased to 100%, without any decrease in specificity.
These results show how important is the evaluation of the available
microbiological methods by different laboratories in different settings.
