TEM-24 extended-spectrum β-lactamase-producing Enterobacter aerogenes: long-term clonal dissemination in French hospitals

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 Xba I 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 β-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 β-lactamase in France was essentially due to the dissemination of a single clone .