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CTX-M-93, a CTX-M variant lacking penicillin hydrolytic activity.
- Source :
-
Antimicrobial agents and chemotherapy [Antimicrob Agents Chemother] 2011 May; Vol. 55 (5), pp. 1861-6. Date of Electronic Publication: 2011 Feb 22. - Publication Year :
- 2011
-
Abstract
- Extended-spectrum β-lactamases (ESBLs) of the CTX-M type are increasingly being reported worldwide, with more than 90 known variants. Clinical Escherichia coli isolate Bre-1 was isolated in 2009 and displayed an unusual ESBL phenotype, made of a synergy image between expanded cephalosporins and clavulanic acid discs and susceptibility to penicillins. E. coli Bre-1 harbored a novel CTX-M-encoding gene, designated bla(CTX-M-93). CTX-M-93 differed from CTX-M-27 by only a single L169Q substitution. Compared to CTX-M-27, CTX-M-93 conferred higher MICs of ceftazidime for E. coli (MIC of 8 versus 1.5 μg/ml) and decreased MICs of other expanded-cephalosporins (MIC of cefotaxime of 1 versus 32 μg/ml) and penicillins (MIC of ticarcillin of 0.5 versus >256 μg/ml). A comparison of enzymatic properties revealed that the L169Q substitution led to a decreased Km for ceftazidime (25.5 versus 330 μM) but decreased hydrolytic activity against good substrates, such as cefotaxime (kcat of 0.6 versus 113 s(-1)), probably owing to the alteration of the omega loop positioning during the catalytic process. The blaCTX-M-93 gene was surrounded by the ISEcp1 and IS903 elements and inserted onto a 150-kb non-self-transferrable IncF-type plasmid. E. coli Bre-1 belongs to phylogroup D and is of multilocus sequence type (MLST) 624, a sequence type found only in rare Spanish CTX-M-14-producing E. coli isolates. We have characterized a novel CTX-M variant, CTX-M-93, lacking significant penicillin hydrolysis but with increased ceftazidime hydrolysis.
- Subjects :
- Anti-Bacterial Agents pharmacology
Ceftazidime pharmacology
Cephalosporins pharmacology
Escherichia coli drug effects
Escherichia coli genetics
Molecular Sequence Data
Mutagenesis, Site-Directed
Phylogeny
Polymerase Chain Reaction
beta-Lactamases genetics
Escherichia coli enzymology
Penicillins metabolism
beta-Lactamases metabolism
Subjects
Details
- Language :
- English
- ISSN :
- 1098-6596
- Volume :
- 55
- Issue :
- 5
- Database :
- MEDLINE
- Journal :
- Antimicrobial agents and chemotherapy
- Publication Type :
- Academic Journal
- Accession number :
- 21343457
- Full Text :
- https://doi.org/10.1128/AAC.01656-10