EPIDEMIOLOGIC-STUDY BY PULSED-FIELD GEL-ELECTROPHORESIS OF AN OUTBREAK OF EXTENDED-SPECTRUM BETA-LACTAMASE-PRODUCING KLEBSIELLA-PNEUMONIAE IN A GERIATRIC HOSPITAL

Twelve cases of infections caused by extended-spectrum beta-lactamase (ESBla)-producing Klebsiella pneumoniae were reported between August 1 991 and March 1993 in the Geriatric Department of the Nimes University Hospital, where these bacteria had not been previously isolated. Rest riction profiles of total genomic DNAs cleaved by XbaI and SpeI were c ompared by pulsed-field gel electrophoresis. The strains that were tes ted included the 12 isolates from K. pneumoniae-infected patients, str ains recovered from rectal swabs of asymptomatic patients in the same ward, and strains isolated in other hospitals in Nimes at the same tim e. The restriction profiles of the 12 isolates and those recovered fro m asymptomatic patients in the same ward were very similar. Over a per iod of more than 1 year, extended-spectrum beta-lactamases were not de tected in K. pneumoniae isolates with restriction patterns different f rom that of the epidemic strain. It seems, therefore, that there was n o transfer of a plasmid or a gene coding for ESBla to strains of K. pn eumoniae that were different from the epidemic strain. At the same tim e, ESBla-producing K. pneumoniae isolates exhibiting restriction endon uclease profiles very different from that of the epidemic strain were isolated from other hospitals in Nimes. None of these strains caused a n outbreak. Pulsed-field gel electrophoresis, which allows precise cha racterization of strains beyond the species level, is a useful tool fo r studying the ESBla-producing K. pneumoniae strains involved in nosoc omial outbreaks.