Inhibitor-sensitive AmpC beta-lactamase variant produced by an Escherichia coli clinical isolate resistant to oxyiminocephalosporins and cephamycins.

ABSTRACT: Escherichia coli HKY28, a ceftazidime-resistant strain isolated from a urine specimen in Japan, produced an inhibitor-sensitive AmpC beta-lactamase variant. The deduced amino acid sequence of the enzyme contained a number of substitutions and a tripeptide deletion (Gly286-Ser287-Asp288) compared with the sequence of native AmpC of E. coli. When the deletion was reverted by a 9-base insertion at the relevant site of ampC in the clone, the typical inhibitor-resistant phenotype of AmpC was restored, while at the same time the levels of resistance to ceftazidime, cefpirome, and cefepime were reduced eightfold or more. Molecular modeling studies indicated that a structural change took place in the H-10 helix as a result of the deletion, and this change caused an alteration of the substrate bind

SUBMITTER: Doi Y 

PROVIDER: S-EPMC434168 | biostudies-literature | 2004 Jul

REPOSITORIES: biostudies-literature