The significance of hospitals as reservoirs for endemic multiresistant Salmonella typhimurium causing infection in urban Brazilian children.

To identify possible sources of multiply drug-resistant Salmonella typhimurium among children in São Paulo, Brazil, we reviewed records of 470 children who had visited eight outpatient clinics from March 1981 to May 1982 and of 28 children who had been admitted to one referral hospital between June and November of 1982, and we examined plasmid profiles of the Salmonella isolates by agarose-gel electrophoresis. S. typhimurium was identified in 37 of these children. Case-control studies showed that children with S. typhimurium infections were more likely to have been hospitalized before onset of diarrhea than were either age-matched children without diarrhea (P = .031) or age-matched children with nonbacterial diarrhea (P = .035). Four distinct plasmid profiles, each of which was temporally clustered, were identified in 20 (67%) of 30 S. typhimurium strains isolated from previously hospitalized children and in two (28%) of seven strains from children not previously hospitalized. Each of three of these four profiles was associated with a different hospital, results suggesting that multiresistant-S. typhimurium infections in São Paulo are often nosocomially acquired.