Characterization of extended-spectrum beta-lactamase-producing Salmonella typhimurium by phenotypic and genotypic typing methods

During 1994, 10 isolates of extended-spectrum beta-lactamase-producing Salm onella typhimurium were recovered from children transferred to our hospital from two different centers. Two additional isolates were recovered from tw o nurses from one of these centers. The aim of this study was to determine if there is any relationship between these isolates. The characterization w as done by phenotypic and genotypic methods: biotyping, phage typing, antib iotic susceptibility pattern determination, plasmid analysis, ribotyping (b y the four endonucleases EcoRI, SmaI, BglII and PvuII), pulsed-field gel el ectrophoresis (PFGE) of genome macrorestriction patterns with XbaI, and ran domly amplified polymorphic DNA (RAPD) pattern determination (with the thre e primers 217 d2, B1, and A3). The same biotype, the same serotype, and an identical antibiotype were found. All isolates were resistant to oxyimino-b eta-lactams, gentamicin, tobramycin, and sulfamethoxazole-trimethoprim. All isolates showed an indistinguishable pattern by ribotyping and very simila r patterns by PFGE and RAPD. The overall results indicated! the spread of:a closely related strain of S. typhimurium in children and nurses.