| Autor: |
Stepanova MN; Institute of Antimicrobial Chemotherapy, Krupskaya str. 28, PO Box 5, Smolensk, Russia., Pimkin M, Nikulin AA, Kozyreva VK, Agapova ED, Edelstein MV |
| Jazyk: |
angličtina |
| Zdroj: |
Antimicrobial agents and chemotherapy [Antimicrob Agents Chemother] 2008 Apr; Vol. 52 (4), pp. 1297-301. Date of Electronic Publication: 2008 Jan 22. |
| DOI: |
10.1128/AAC.01060-07 |
| Abstrakt: |
We report on a novel CTX-M extended-spectrum beta-lactamase (ESBL), designated CTX-M-42, with enhanced activity toward ceftazidime. CTX-M-42 was identified in a hypermutable Escherichia coli nosocomial isolate (isolate Irk2320) and is a Pro167Thr amino acid substitution variant of CTX-M-3. By molecular typing of ESBL-producing E. coli strains previously isolated in the same hospital ward, we were able to identify a putative progenitor (strain Irk1224) of Irk2320, which had a mutator phenotype and harbored the CTX-M-3 beta-lactamase. To reproduce the natural evolution of CTX-M-3, we selected for ceftazidime resistance mutations in bla CTX-M-3 gene in vitro both in clinical isolate Irk1224 and in laboratory-derived hypermutable (mutD5) strain GM2995. These experiments yielded CTX-M-3 Pro167Ser and CTX-M-3 Asn136Lys mutants which conferred higher levels of resistance to ceftazidime than to cefotaxime. CTX-M-3 Asn136Lys had a level of low activity toward ampicillin, which may explain its absence from clinical isolates. We conclude that the selection of CTX-M-42 could have occurred in vivo following treatment with ceftazidime and was likely facilitated by the hypermutable background. |
| Databáze: |
MEDLINE |
| Externí odkaz: |
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