Outbreak of infection with extended-spectrum beta-lactamase-producing Klebsiella pneumoniae in a Mexican hospital

Thirty-one strains of Klebsiella pneumoniae (including 10 duplicates) from 21 septicemic pediatric patients (age, <2 months) were studied during a 4-m onth period (June to October 1996) in which the fatality rate was 62% (13 o f 21). These isolates identified by the API 20E system yielded the same bio type. Pulsed-field gel electrophoresis experiments revealed the same clone in 31 strains. The isolates were multidrug-resistant but were still suscept ible to ciprofloxacin, imipenem, and cefoxitin. A 135-kb plasmid was harbor ed in all of the isolates. No transconjugants were obtained that were resis tant to ampicillin, cefotaxime, tetracycline, or gentamicin. Isoelectric fo cusing for <beta>-lactamases was performed on all strains, and three bands with pIs of 5.4, 7.6, and 8.2 were obtained. Of these, the pI 8.2 beta -lac tamase had an extended-spectrum beta -lactamase phenotype. PCR amplificatio n of both TEM- and SHV-type genes was obtained. The sequence analysis of th e SHV PCR product indicated a mutation corresponding to the SHV-5 beta -lac tamase.