Objective: To investigate interstrain relatedness of TEM-24-producing Enterobacter aerogenes clinical strains isolated between 1993 and 1998 in 10 French hospitals from nine areas by pulsed-field gel electrophoresis (PFGE) and plasmid patterns.
Methods: Fifteen TEM-24-producing strains and a set of 16 control strains having various other antibiotic resistance phenotypes were genotyped by PFGE. Plasmid DNA from TEM-24-producing strains and transconjugants was analyzed.
Results: Analysis of XbaI macrorestriction patterns revealed only minor variations, and showed that all 15 TEM-24-producing strains were closely related. Some isolates originating from distant areas had indistinguishable patterns. According to their clustering correlation coefficients, they were also genomically distant from the control strains. Two plasmid patterns were observed in TEM-24-producing strains, one of them in 13 of the strains. Large plasmids of 85 kb encoding TEM-24 beta-lactamase were present in all isolates and, in all except one strain, could be transferred with high frequency by conjugation.
Conclusions: These results confirm that the spread of the TEM-24 extended-spectrum beta-lactamase in France was essentially due to the dissemination of a single clone.