title: High prevalence of stably derepressed class-I beta-lactamase expression in multiresistant clinical isolates of Enterobacter cloacae from Greek hospitals.
abstract: Susceptibilities to cefotaxime (Ctx) and ceftazidime (Caz) were examined for 90 recent clinical isolates of Enterobacter cloacae from Greek hospitals. Most (68%) of the isolates were resistant to both drugs, and all were resistant to cefoxitin. beta-Lactamase activities against cephaloridine in crude extracts from Ctx-Caz-resistant isolates were high, irrespective of whether or not the cells were grown with cefoxitin as an inducer of the chromosomal beta-lactamase, indicating stable derepression of the gene for the enzyme. On the other hand, double disk antagonism tests showed that all the Ctx-Caz-sensitive isolates possessed inducible expression of this beta-lactamase. Iso-electric focusing revealed the presence of five forms of the chromosomal beta-lactamase, randomly distributed amongst the Ctx-Caz-resistant and -sensitive isolates. Plasmid-mediated beta-lactamases of TEM and PSE types also were found in many isolates. These data indicate that the extremely high prevalence of Ctx-Caz-resistant E. cloacae isolates in Greek hospitals is attributed to the dissemination of mutants which constitutively overproduce the class-I chromosomal beta-lactamase. Over 90% of these isolates exhibited cross-resistance to aminoglycosides, suggesting the accumulation of unrelated antibiotic resistance mechanisms.
authors.affiliation: Department of Bacteriology, Hellenic Pasteur Institute, Athens, Greece.
authors.forename: E
authors.initials: E
authors.lastname: Tzelepi
authors.forename: L S
authors.initials: LS
authors.lastname: Tzouvelekis
authors.forename: A C
authors.initials: AC
authors.lastname: Vatopoulos
authors.forename: A F
authors.initials: AF
authors.lastname: Mentis
authors.forename: A
authors.initials: A
authors.lastname: Tsakris
authors.forename: N J
authors.initials: NJ
authors.lastname: Legakis
mesh_terms: D002439:Cefotaxime / Q000494:pharmacology*; D002442:Ceftazidime / Q000494:pharmacology*; D004352:Drug Resistance, Microbial; D016972:Enterobacter cloacae / Q000187:drug effects / Q000201:enzymology* / Q000235:genetics; D004756:Enterobacteriaceae Infections / Q000453:epidemiology; D004790:Enzyme Induction; D004794:Enzyme Repression; D006115:Greece / Q000453:epidemiology; D006801:Humans; D007525:Isoelectric Focusing; D008826:Microbial Sensitivity Tests; D010405:Penicillinase / Q000235:genetics*; D015995:Prevalence
chemical_list: D002442:Ceftazidime; D010405:Penicillinase; D002439:Cefotaxime