PULSED-FIELD GEL-ELECTROPHORESIS GENOMIC FINGERPRINTING OF HOSPITAL ESCHERICHIA-COLI BACTEREMIA ISOLATES

Pulsed-field gel electrophoresis (PFGE), because of the increased sens itivity it affords over other methods of bacterial genotyping, represe nts a potentially powerful tool for the characterisation of isolates f rom hospital infections, Genomic fingerprinting by PFGE was applied to all clinical isolates of Escherichia coli obtained from blood during a 6-month period (78 isolates, 58 patients) at the University of Michi gan Medical Center. The rare-restriction patterns of these isolates, i n contrast to those of isolates from the E. coli reference collection (ECOR), were not randomly distributed through the E. coli species. Fou r related clusters, which represented c. 21% of the blood isolates, we re identified, Two of these genotypic clusters were also clustered tem porally, their members all being isolated within the same 2-week perio d, while the other two clusters spanned the study period. These observ ations indicate in-hospital endemic vectors or the occurrence of speci alised E. coli lineages that are capable of invading the bloodstream a nd exploiting in-hospital vectors, or both.