Temporal evolution of the prevalence of methicillin-resistant Staphylococcus aureus in a tertiary hospital in Bahia, Brazil: a nine-year evaluation study.

Infections caused by methicillin-resistant Staphylococcus aureus (MRSA) have become an increasing problem in Brazilian hospitals within the last years. In Bahia, there is scarce information on the epidemiological characteristics of MRSA infections and their determinants. The objective of this study was to evaluate the temporal evolution of MRSA infections in a private, tertiary hospital, in Salvador, the capital of the state of Bahia. We reviewed the microbiological records of bacterial isolates from the Hospital Espanhol, a 300 bed, general hospital, in Salvador. We analyzed the frequency of positive cultures for S. aureus during the last nine years, the prevalence of MRSA, and the spatial distribution of the isolates in the hospital. We also evaluated the temporal evolution of MRSA during the study period. Seven-hundred-ten cultures were positive for S. aureus from 1996 through 2004. The prevalence of MRSA was 28%. The intensive care unit (59%), the hemodyalisis unit (43%), and the infectious diseases unit (34%) presented with significantly higher prevalence of MRSA, when compared to the remaining clinics of the hospital. We detected a significant increase of MRSA isolation among patients with nosocomial infections, over time (P<0.0001). MRSA isolates were highly resistant to alternative drugs (clyndamicin, erythromycin, co-trimexazole, levofloxacin), reinforcing the likelihood of nosocomial acquisition of the pathogen. The overall prevalence of MRSA in the hospital has remained relatively stable within the last nine years, but there was a significant trend forincreasing nosocomial acquisition of MRSA over time, which is even higher for patients attended in intensive care units, HDU, or IDU.