Oxacillin-hydrolyzing beta-lactamase involved in resistance to imipenem in Acinetobacter baumannii.
Acinetobacter baumannii strain A148, a clinical isolate resistant to imipenem (MIC = 32 mg l-1), synthesized two beta-lactamases with pIs 6.3 and > 9.2. The pI 6.3 enzyme hydrolyzed the penicillins, including isoxazoylpenicillins, first-, second- and, to a lesser extent, third-generation cephalosporins. It was inhibited by chloride ions and by the penem beta-lactamase inhibitor BRL 42715. Clavulanate was a weak inhibitor and EDTA did not affect the beta-lactamase activity. This enzyme also hydrolyzed imipenem with a catalytic efficiency (Kcat/Km) of 1500 mM-1 s-1. Moreover, this purified beta-lactamase produced a positive microbiological clover-leaf test with imipenem. Therefore, the pI 6.3 beta-lactamase was considered to be involved in the imipenem resistance of A. baumannii strain A148.
Hornstein
M
M
Service de Bactériologie-Virologie, Centre Hospitalier Universitaire Avicenne, Université Paris Nord, Bobigny, France.
Sautjeau-Rostoker
C
C
Péduzzi
J
J
Vessières
A
A
Hong
L T
LT
Barthélémy
M
M
Scavizzi
M
M
Labia
R
R
D000150:Acinetobacter / Q000187:drug effects* / Q000201:enzymology; D000900:Anti-Bacterial Agents / Q000494:pharmacology; D002511:Cephalosporins / Q000378:metabolism; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006868:Hydrolysis; D015378:Imipenem / Q000494:pharmacology*; D007526:Isoelectric Point; D007700:Kinetics; D007769:Lactams; D008970:Molecular Weight; D010068:Oxacillin / Q000378:metabolism*; D010406:Penicillins / Q000378:metabolism; D012965:Sodium Chloride / Q000494:pharmacology; D013379:Substrate Specificity; D013845:Thienamycins / Q000494:pharmacology*; D018440:beta-Lactam Resistance / Q000502:physiology*; D065093:beta-Lactamase Inhibitors; D001618:beta-Lactamases / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism*; D047090:beta-Lactams
D000900:Anti-Bacterial Agents; D002511:Cephalosporins; D004791:Enzyme Inhibitors; D007769:Lactams; D010406:Penicillins; D013845:Thienamycins; D065093:beta-Lactamase Inhibitors; D047090:beta-Lactams; C061593:C6-(N1-methyl-1,2,3-trazolylmethylene)penem; D012965:Sodium Chloride; D015378:Imipenem; D001618:beta-Lactamases; D010068:Oxacillin