[Identification of a cephalosporinase susceptible to clavulanic acid in a clinical strain of Serratia fonticola].
We analyzed the beta-lactamase production of a Serratia fonticola isolated for its resistance to cefuroxime (Minimum Inhibitory Concentration > 256 mg/l) in December 1993 from a patient hospitalized in Meaux. The wild strain was resistant to amoxycillin but sensitive to augmentin, that suggested the production of a beta-lactamase susceptible to clavulanic acid. For the wild strain, beta-lactamase production was inducible and only one enzyme with an isoelectric point of 8.12 was detected. beta-lactamase production was 16 mU/mg for non-induced extracts and ranged from 100 to 230 mU/mg in the presence of inducing beta-lactams (enzyme activity was measured with penicillin G as substrate). On a Szybalski gradient a constitutive strain was obtained. Its enzyme production was 13,000 mU/mg. The kinetics and isoelectric points of the enzymes produced by the two strains were identical. This beta-lactamase hydrolyzes penicillins (amoxycillin: Vm = 60 relative to penicillin G = 100, ticarcillin: 15), first generation cephalosporins (cephalothin Vm = 930). However, this enzyme hydrolyzes efficiently oxyimino-cephalosporins: cefuroxime (Vm = 70) and cefotaxime (Vm = 120), but cephamycins are not substrates. Clavulanic acid has a very good affinity for this beta-lactamase (Ki = 0.09 microM) which is inactivated progressively (I50 = 0.045 microgram/ml). These properties shows some similarities with those of the class A beta-lactamases of P. vulgaris RO104 (pI = 8.3), P. penneri 14HBC (pI = 6.65) and the plasmid-mediated extended-spectrum MEN-1 (pI = 8.4).
Farzaneh
S
S
Muséum National d'Histoire Naturelle, URA 401, CNRS, Paris, France.
Péduzzi
J
J
Demachy
M C
MC
Barthélémy
M
M
Labia
R
R
D000368:Aged; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D002510:Cephalosporinase / Q000737:chemistry / Q000302:isolation & purification* / Q000493:pharmacokinetics; D019818:Clavulanic Acid; D002969:Clavulanic Acids / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005260:Female; D006801:Humans; D066298:In Vitro Techniques; D007525:Isoelectric Focusing; D012705:Serratia / Q000187:drug effects / Q000201:enzymology* / Q000302:isolation & purification
D000900:Anti-Bacterial Agents; D002969:Clavulanic Acids; D004791:Enzyme Inhibitors; D019818:Clavulanic Acid; D002510:Cephalosporinase
Identification dans une souche clinique de Serratia fonticola d'une céphalosporinase sensible à l'acide clavulanique.