Dataset Information

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 binding site, leading to a unique phenotype analogous to that of inhibitor-sensitive class A extended-spectrum beta-lactamases. The degree of inhibition was greater with sulbactam and tazobactam than with clavulanic acid. To our knowledge, this is the first report to have characterized an E. coli ampC that encodes chromosomal AmpC beta-lactamase sensitive to the available beta-lactamase inhibitors.

SUBMITTER: Doi Y

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

REPOSITORIES: biostudies-literature

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

Doi Yohei Y Wachino Jun-ichi J Ishiguro Masaji M Kurokawa Hiroshi H Yamane Kunikazu K Shibata Naohiro N Shibayama Keigo K Yokoyama Keiko K Kato Haru H Yagi Tetsuya T Arakawa Yoshichika Y

Antimicrobial agents and chemotherapy 20040701 7

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 ...[more]

PMID: 15215122

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Project description:A nationwide study on the occurrence of extended-spectrum ?-lactamase (ESBL)/AmpC in nonhospitalized horses in the Netherlands was performed. Molecular characterization was done, and questionnaires were analyzed to identify factors associated with carriage. In total, 796 horse owners were approached; 281 of these submitted a fecal sample from their horse(s), resulting in 362 samples. All samples were cultured qualitatively in Luria-Bertani (LB) broth and subsequently on MacConkey agar, both supplemented with 1?mg/liter cefotaxime (LB+ and MC+). Positive samples were subsequently cultured quantitatively on MC+. Initial extended-spectrum-?-lactamase (ESBL)/AmpC screening was performed by PCR, followed by whole-genome sequencing on selected strains. Associations between ESBL/AmpC carriage and questionnaire items were analyzed using a univariate generalized estimating equation (GEE) regression analysis, followed by a multiple GEE model for relevant factors. In total, 39 of 362 samples (11%) were determined to be positive for ESBL/AmpC. bla CTX-M-1-carrying isolates were obtained from 77% of positive samples (n?=?30). Other ESBL/AmpC genes observed included bla CTX-M-2, bla CTX-M-14, bla CTX-M-15, bla CTX-M-32, bla SHV-12, bla CMY-2, and bla ACT-10 A high association between the presence of bla CTX-M-1 and IncHI1 plasmids was observed (46% of samples; n?=?18). Based on core genome analysis (n?=?48 isolates), six Escherichia coli clusters were identified, three of which represented 80% of the isolates. A negative association between ESBL/AmpC carriage and horses being in contact with other horses at a different site was observed. The presence of a dog on the premises and housing in a more densely human-populated region were positively associated.IMPORTANCE Extended-spectrum ?-lactamases (ESBLs) are widespread in human and animal populations and in the environment. Many different ESBL variants exist. The dissemination of ESBLs within and between populations and the environment is also largely influenced by genetic mobile elements (e.g., plasmids) that facilitate spread of these ESBLs. In order to identify potential attributable ESBL sources for, e.g., the human population, it is important to identify the different ESBL variants, the bacteria carrying them, and the potential risk factors for ESBL carriage from other potential sources. This nationwide study focuses on ESBL carriage in the open horse population and investigated the molecular characteristics, geographical distribution throughout the Netherlands, and potential risk factors for fecal ESBL carriage in horses. These data can be used for future attribution studies in order to reduce potential transmission of ESBL-producing bacteria between sources.

Dataset Information

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

Publications

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

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