Pulsed-field gel electrophoresis genomic fingerprinting of hospital Escherichia coli bacteraemia isolates

Pulsed-field gel electrophoresis (PFGE), because of the increased sensitivity it affords over other methods of bacterial genotyping, represents a potentially powerful tool for the characterisation of isolates from 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 Michigan Medical Center. The rare-restriction patterns of these isolates, in contrast to those of isolates from the E. coli reference collection (ECOR), were not randomly distributed through the E. coli species. Four related clusters, which represented c. 21% of the blood isolates, were identified, Two of these genotypic clusters were also clustered temporally, their members all being isolated within the same 2-week period, while the other two clusters spanned the study period. These observations indicate in-hospital endemic vectors or the occurrence of specialised E. coli lineages that are capable of invading the bloodstream and exploiting in-hospital vectors, or both.