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

Objective To investigate interstrain relatedness of TEM-24 -producing Enter obacter aerogenes clinical strains isolated between 1993 and 1998 in 10 Fre nch hospitals From nine areas by pulsed-field gel electrophoresis (PFGE) an d plasmid patterns. Methods Fifteen TEM-24 -producing strains and a set of 16 control strains h aving various other antibiotic resistance phenotypes were genotyped by PFGE , Plasmid DNA from TEM-24-producing strains and tranconjugants was analyzed . Results Analysis of XbaI macrorestriction patterns revealed only minor vari ations, and showed that all 15 TEM-24 -producing strains were closely relat ed. Some isolates originating from distant areas had indistinguishable patt erns. According to their clustering correlation coefficients, they were als o genomically distant from the control strains. Two plasmid patterns were o bserved in TEM-24-producing strains, one of them in 13 of the strains. Larg e plasmids of 85 kb encoding TEM-24 beta-lactamase were present in all isol ates and, in all except one strain, could be transferred with high frequenc y by conjugation. Conclusions These results confirm that the spread of the TEM-24 extended-sp ectrum beta-lactamase in France was essentially due to the dissemination of a single done.