title: Does high level production of SHV-type penicillinase confer resistance to ceftazidime in Enterobacteriaceae?
abstract: We report the isolation of a clinical isolate of Klebsiella pneumoniae that showed resistance to ceftazidime (MIC: 8 micrograms/ml), susceptibility to aztreonam (MIC: 2 micrograms/ml) and cefotaxime (MIC: 0.015 micrograms/ml). A synergistic effect between clavulanic acid and ceftazidime or aztreonam against this strain was also observed. The strain hyperproduced SHV-1 penicillinase (990 U/g) which is encoded by a self-transferrable plasmid of at least 150 kb. That the ceftazidime-resistance phenotype could be due to hyperproduction of SHV-1 penicillinase is supported by the study of a spontaneous ceftazidime-resistant mutant in vitro obtained from an Escherichia coli strain containing plasmid p453 encoding the SHV-1. Indeed, this mutant hyperproducing SHV-1 (2200 U/g) was resistant to ceftazidime (MIC: 16 micrograms/ml) and aztreonam (MIC: 8 micrograms/ml) but susceptible to cefotaxime (MIC: 0.03 ng/ml). Clavulanic acid showed a synergistic effect when associated with ceftazidime or aztreonam. In contrast, the hyperproduction of TEM-1 (790 U/g) did not confer a ceftazidime- and aztreonam-resistant phenotype while hyperproduction of both TEM-1 and SHV-1 increased the resistance to amoxycillin/clavulanic acid and to cephalothin.
authors.affiliation: Muséum National d'Histoire Naturelle, URA 401 CNRS, Paris, France.
authors.forename: A
authors.initials: A
authors.lastname: Petit
authors.forename: H
authors.initials: H
authors.lastname: Ben Yaghlane-Bouslama
authors.forename: L
authors.initials: L
authors.lastname: Sofer
authors.forename: R
authors.initials: R
authors.lastname: Labia
mesh_terms: D002442:Ceftazidime / Q000494:pharmacology*; D019818:Clavulanic Acid; D002969:Clavulanic Acids / Q000494:pharmacology; D004347:Drug Interactions; D004352:Drug Resistance, Microbial; D004359:Drug Therapy, Combination; D004755:Enterobacteriaceae / Q000187:drug effects; D007711:Klebsiella pneumoniae / Q000187:drug effects*; D001618:beta-Lactamases / Q000378:metabolism*
chemical_list: D002969:Clavulanic Acids; D019818:Clavulanic Acid; D002442:Ceftazidime; C054882:beta-lactamase PIT-2; D001618:beta-Lactamases