Multiplicity of TEM-derived beta-lactamases from Klebsiella pneumoniae strains isolated at the same hospital and relationships between the responsible plasmids.
Five plasmid-mediated beta-lactamases conferring high-level resistance to ceftazidime were isolated from Klebsiella pneumoniae strains in the same hospital. These enzymes had isoelectric points ranging from 5.3 to 6.5 (CAZ-1, 5.55; CAZ-2, 6.0; CAZ-3, 5.3; CAZ-6, 6.5; and CAZ-7, 6.3). All isolates and their Escherichia coli transconjugants were highly resistant to amoxicillin (MICs, greater than 4,096 micrograms/ml), piperacillin (64 to 256 micrograms/ml), cephalothin (32 to 256 micrograms/ml), and ceftazidime (32 to 512 micrograms/ml) but remained moderately susceptible to cefotaxime (0.5 to 8 micrograms/ml). Only CAZ-6- and CAZ-7-producing strains were highly resistant to aztreonam (64 to 128 micrograms/ml). All the isolates remained susceptible to moxalactam and imipenem. The reduced activity of piperacillin, cefotaxime, ceftazidime, or aztreonam was restored by 2 micrograms of clavulanate, sulbactam, tazobactam, or brobactam per ml for E. coli producing CAZ-2, CAZ-3, and CAZ-7. Sulbactam had a lower protective effect than other inhibitors for E. coli harboring CAZ-1 and especially CAZ-6. Except for CAZ-1, which was mediated by a 150-kilobase (kb) plasmid (pCFF14), the other ceftazidimases were mediated by plasmids of 85 kb with EcoRI digestion patterns similar to that of pCFF04 encoding CTX-1 beta-lactamase. A TEM probe hybridized with a 19-kb EcoRI fragment of all these closely related plasmids.
Chanal
C M
CM
Service de Bactériologie, Faculté de Médecine et Pharmacie, Clermont-Ferrand, France.
Sirot
D L
DL
Petit
A
A
Labia
R
R
Morand
A
A
Sirot
J L
JL
Cluzel
R A
RA
D003227:Conjugation, Genetic; D004262:DNA Restriction Enzymes; D004269:DNA, Bacterial / Q000235:genetics; D004352:Drug Resistance, Microbial / Q000235:genetics*; D007525:Isoelectric Focusing; D007700:Kinetics; D007711:Klebsiella pneumoniae / Q000187:drug effects / Q000201:enzymology* / Q000235:genetics; D008826:Microbial Sensitivity Tests; D009693:Nucleic Acid Hybridization; D010957:Plasmids; D001618:beta-Lactamases / Q000302:isolation & purification / Q000378:metabolism*
D004269:DNA, Bacterial; D004262:DNA Restriction Enzymes; D001618:beta-Lactamases