Novel transferable extended-spectrum beta-lactamase (SHV-6) from Klebsiella pneumoniae conferring selective resistance to ceftazidime.
A clinical isolate of Klebsiella pneumoniae sensu lato isolated from throat and a blood culture taken from a neutropenic patient treated for 2 weeks with ceftazidime and vancomycin was resistant to ceftazidime (MIC: 32 micrograms/ml) and moderately susceptible to aztreonam (MIC: 4 micrograms/ml). The isolate contained a plasmid of 180 kb which, when transferred to Escherichia coli by conjugation, conferred resistance to ceftazidime and tetracycline. The transconjugant had decreased susceptibility to ceftazidime (128-fold) and aztreonam (8-fold). Clavulanic acid and sulbactam each inhibited the resistance and clavulanic acid showed a synergistic effect when associated with ceftazidime and aztreonam. An extended-spectrum beta-lactamase with an isoelectric point of 7.6 was detected in the clinical isolates from blood and its transconjugant. This beta-lactamase showed similar substrate and inhibition profiles to SHV-1. In particular it did not hydrolyse ceftazidime. Hybridization with an intragenic probe for SHV-3 indicates that this beta-lactamase is an SHV-type enzyme. We propose that this novel CAZ-type extended-spectrum beta-lactamase be named SHV-6.
Arlet
G
G
Laboratoire de Microbiologie, Hôpital Saint-Louis, Paris, France.
Rouveau
M
M
Bengoufa
D
D
Nicolas
M H
MH
Philippon
A
A
D002442:Ceftazidime / Q000494:pharmacology*; D003227:Conjugation, Genetic; D004352:Drug Resistance, Microbial / Q000235:genetics; D007711:Klebsiella pneumoniae / Q000187:drug effects / Q000201:enzymology*; D008826:Microbial Sensitivity Tests; D009693:Nucleic Acid Hybridization; D010957:Plasmids; D001618:beta-Lactamases / Q000032:analysis*
D002442:Ceftazidime; D001618:beta-Lactamases