Penicillin-Resistant Mechanisms in Pseudomonas aeruginosa : Effects of Penicillin G and Carbenicillin on Transpeptidase and d -Alanine Carboxypeptidase Activities

Abstract
A membrane fraction from Pseudomonas aeruginosa KM 338 was shown to catalyze in vitro peptidoglycan synthesis from uridine 5′-diphosphate- N -acetylmuramyl- l -alanyl- d - glutamyl-meso-diaminopimelyl- d -alanyl- d -alanine and uridine 5′-diphosphate- N -acetylglucosamine. Synthesized peptidoglycan was partially cross-linked by transpeptidation, which was accompanied by the release of d -alanine. This reaction was strongly inhibited by 25 and 50 μg of penicillin G and carbenicillin per ml respectively, whereas the intact cells were relatively resistant to penicillins (minimal inhibitory concentration of penicillin G and carbenicillin, 30 and 0.125 mg/ml, respectively). Soluble d -alanine carboxypeptidase present in P. aeruginosa KM 338 was studied as well, which was found almost completely inhibited by penicillin G and carbenicillin (10 μg/ml).

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