Multiply resistant Klebsiella pneumoniae strains from two Chicago hospitals: identification of the extended-spectrum TEM-12 and TEM-10 ceftazidime-hydrolyzing beta-lactamases in a single isolate.
Ceftazidime-resistant Klebsiella pneumoniae strains began to appear when ceftazidime usage was increased in two unrelated Chicago hospitals. These strains produced a beta-lactamase with an isoelectric point of 5.6 (RP-5.6) and strong hydrolyzing activity against ceftazidime. Two different restriction digest profiles were associated with the ceftazidime resistance plasmids. A second beta-lactamase with a pI of 5.2 (RP-5.2) was coproduced in two representative strains. The second beta-lactamase hydrolyzed ceftazidime, cefotaxime, and aztreonam with relative hydrolysis rates of < 8% of that observed for benzylpenicillin. Both enzymes were inhibited by clavulanic acid and tazobactam. Nucleotide sequencing of the genes coding for RP-5.2 and RP-5.6 revealed sequences identical to those of the TEM-12 and TEM-10 beta-lactamase genes, respectively. Both genes were derived from a TEM-1 sequence related to that of the gene encoded on the Tn2 transposon. Single point mutations are required to progress from TEM-1 to TEM-12 and from TEM-12 to TEM-10. Extracts from broths grown from single cell isolates of the strain producing TEM-12 and TEM-10 were shown to contain both enzymes. Transconjugants producing either the TEM-12 or the TEM-10 beta-lactamase were obtained. A significant finding was that both enzymes were encoded by plasmids with identical restriction digest patterns. These studies show that mutations leading to extended-spectrum beta-lactamases can occur sequentially in the same organism, with the genes encoding both enzymes maintained stably.
Bradford
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PA
Medical Research Division, American Cyanamid Company, Pearl River, New York, 10965.
Cherubin
C E
CE
Idemyor
V
V
Rasmussen
B A
BA
Bush
K
K
D000900:Anti-Bacterial Agents / Q000494:pharmacology; D001483:Base Sequence; D002442:Ceftazidime / Q000378:metabolism*; D004269:DNA, Bacterial / Q000235:genetics; D004352:Drug Resistance, Microbial; D004926:Escherichia coli / Q000235:genetics; D006801:Humans; D007710:Klebsiella Infections / Q000382:microbiology*; D007711:Klebsiella pneumoniae / Q000187:drug effects* / Q000201:enzymology* / Q000235:genetics; D008826:Microbial Sensitivity Tests; D008969:Molecular Sequence Data; D010957:Plasmids; D017422:Sequence Analysis, DNA; D065093:beta-Lactamase Inhibitors; D001618:beta-Lactamases / Q000032:analysis / Q000235:genetics / Q000302:isolation & purification*
D000900:Anti-Bacterial Agents; D004269:DNA, Bacterial; D065093:beta-Lactamase Inhibitors; D002442:Ceftazidime; C084251:beta-lactamase TEM-10; C088328:beta-lactamase TEM-12; D001618:beta-Lactamases