title: Biochemical characteristics of a carbapenemase from an Acinetobacter baumannii isolate collected in Buenos Aires, Argentina.
abstract: Three carbapenem-resistant Acinetobacter baumannii isolates were collected at a hospital in Buenos Aires, Argentina. Isoelectric focusing revealed multiple beta-lactamases, with two of the isolates showing identical profiles. A pI 6.9 carbapenemase with a molecular weight of 30 kDa was purified from one of these two isolates. The enzyme was predominantly a penicillinase, with its highest Vmax for oxacillin but highest Vmax/Km for benzylpenicillin. First-generation cephalosporins and imipenem were weaker substrates than penicillins, and oxyimino-aminothiazolyl cephalosporins were essentially stable. Meropenem-hydrolysing activity was not detected, despite resistance. The carbapenemase was inhibited by clavulanic acid and tazobactam, but not by EDTA. These kinetics place the enzyme into functional group 2; as an oxacillinase it could be placed in sub-group 2d or, as a zinc-independent carbapenemase, in sub-group 2f.
authors.affiliation: Antibiotic Reference Unit, Central Public Health Laboratory, London, UK.
authors.forename: M
authors.initials: M
authors.lastname: Afzal-Shah
authors.forename: H E
authors.initials: HE
authors.lastname: Villar
authors.forename: D M
authors.initials: DM
authors.lastname: Livermore
mesh_terms: D000150:Acinetobacter / Q000187:drug effects / Q000201:enzymology* / Q000302:isolation & purification; D001118:Argentina; D001426:Bacterial Proteins; D015780:Carbapenems; D006801:Humans; D015378:Imipenem / Q000378:metabolism / Q000494:pharmacology; D007525:Isoelectric Focusing; D000077731:Meropenem; D008826:Microbial Sensitivity Tests; D008970:Molecular Weight; D013045:Species Specificity; D013183:Sputum / Q000382:microbiology; D013845:Thienamycins / Q000378:metabolism / Q000494:pharmacology; D014556:Urine / Q000382:microbiology; D018440:beta-Lactam Resistance / Q000235:genetics; D001618:beta-Lactamases / Q000737:chemistry* / Q000187:drug effects / Q000378:metabolism*
chemical_list: D001426:Bacterial Proteins; D015780:Carbapenems; D013845:Thienamycins; D015378:Imipenem; D001618:beta-Lactamases; C063912:carbapenemase; D000077731:Meropenem