Comparison of macrorestriction analysis of genomic DNA by pulsed-field gel electrophoresis and ribotyping with conventional methods for differentiation of Escherichia coli 0124 isolates

ObjectiveTo evaluate the usefulness of different phenotypic and genotypic markers for epidemiological typing of enteroinvasive Escherichia coli 0124 (EIEC 0124).MethodsSeven sporadic EIEC 0124 isolates and 22 isolates from two different outbreaks were characterized. Chromosomal deoxyribonucleic acid (DNA) macrorestriction analysis with XbaI resolved by pulsed-field gel electrophoresis (PFGE) and ribotyping with each of the three restriction endonucleases BglII EcoRI, and ClaI were compared with biotyping, antimicrobial susceptibility patterns and plasmid profiles.ResultsBiotypes and antimicrobial resistance profiles of the outbreak-associated strains showed considerable variation, thereby limiting the usefulness of such phenotypic markers. Only 57% of the sporadic isolates harbored plasmids. Three different ribotypes based on 5 to 7 bands were recorded among sporadic isolates whereas all outbreak-associated strains showed the same ribotype. BglII appeared to give the best discrimination whereas EcoRI and ClaI provided no additional information. Sporadic EIEC 0124 isolates showed a marked diversity of macrorestriction patterns (similarity coefficient 58 to 93%) and five different patterns were detected. In contrast, the outbreak isolates were closely related (similarity coefficient 90 to 100%). Genomic DNA macrorestriction analysis correlated well with ribotyping, but PFGE was more discriminating.ConclusionsPFGE is a useful method for epidemiological comparison and differentiation of EIEC 0124 isolates