Molecular characterization of a cephamycin-hydrolyzing and inhibitor-resistant class A beta-lactamase, GES-4, possessing a single G170S substitution in the omega-loop.

ABSTRACT: The nosocomial spread of six genetically related Klebsiella pneumoniae strains producing GES-type beta-lactamases was found in a neonatal intensive care unit, and we previously reported that one of the six strains, strain KG525, produced a new beta-lactamase, GES-3. In the present study, the molecular mechanism of cephamycin resistance observed in strain KG502, one of the six strains described above, was investigated. This strain was found to produce a variant of GES-3, namely, GES-4, which was responsible for resistance to both cephamycins (cefoxitin MIC, >128 microg/ml) and beta-lactamase inhibitors (50% inhibitory concentration of clavulanic acid, 15.2 +/- 1.7 microM). The GES-4 enzyme had a single G170S substitution in the Omega-loop region compared with the GES-3 sequence. This single

SUBMITTER: Wachino J 

PROVIDER: S-EPMC478515 | biostudies-literature | 2004 Aug

REPOSITORIES: biostudies-literature