[Antimicrobial sensitivity profile of Staphylococcus aureus at a pediatric hospital: prevalence of resistance to methicillin].

Methicillin-resistant Staphylococcus aureus (MRSA) has become a significant cause of nosocomial infections. In efforts to delineate the magnitude of this problem, we determined the prevalence of MRSA in community acquired (n = 382) and nosocomial strains (n = 207) of S. aureus isolated between Jan 1986 and March 1989. Antimicrobial susceptibility was evaluated using an agar dilution method (Muller-Hinton agar supplemented with 4% NaCl incubated to 35 degrees C for 24 h) and MIC breakpoints were determined according to NCCLS standards. We detected (24.2%) MRSA in nosocomial strains and (5%) MRSA in community acquired strains (P less than 0.05), with a global prevalence of 11.7%. The susceptibility of community acquired S. aureus was 90% or higher for dicloxacillin, cephalothin, sulbactam/ampicillin (S/A), clindamycin, rifampicin and amikacin; 85% for cefotaxime and SMX/TMP and only 75% for erythromycin. The susceptibility pattern of the nosocomial strains was consistent with the prevalence of MRSA but the susceptibility for cephalothin, amikacin and sulbactam/ampicillin was 84.4%, 89.4% and 86.5% respectively, significantly higher than for methicillin (P less than 0.05). Although the increased susceptibility for cephalothin and amikacin has been reported for MRSA before, the published reports using these antibiotics in the treatment of MRSA infections are controversial. The increased susceptibility of MRSA to S/A could be explained in part if the MR was mediated by "acquired MR" attributable to B-lactamase production. Our data provide a perspective on the magnitude of MRSA as a problem in a pediatric teaching hospital in Mexico. Moreover, if taken at face value, the in vitro susceptibility data point to various potential treatment options which warrant clinical evaluation.