Dissemination of CTX-M-Type Extended-Spectrum -Lactamase Genes to Unusual Hosts (original) (raw)
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Antimicrobial Agents and Chemotherapy, 2007
Of the 181 unduplicated Escherichia coli strains isolated in nine different hospitals in three Portuguese regions, 119 were extended-spectrum -lactamase (ESBL)-CTX-M producers and were selected for phenotype and genotype characterization. CTX-M producer strains were prevalent among community-acquired infections (56%), urinary tract infections (76%), and patients >60 years old (76%). In MIC tests, all strains were resistant to cefotaxime, 92% were resistant to ceftazidime, 93% were resistant to quinolones, 89% were resistant to aminoglycoside, and 26% were resistant to trimethoprim-sulfamethoxazole; all strains were sensitive to carbapenems, and 92% of the strains had a multidrug resistance phenotype. Molecular methods identified 109 isolates harboring a bla CTX-M-15 gene, 1 harboring the bla CTX-M-32 gene (first identification in the country), and 9 harboring the bla CTX-M-14 gene. All isolates presented the ISEcp1 element upstream from the bla CTX-M genes; one presented the IS903 element (downstream of bla CTX-M-14 gene), and none had the IS26 element; 85% carried bla TEM-1B , and 84% also carried a bla OXA-30 . Genetic relatedness analysis based on pulsed-field gel electrophoresis defined five clusters and indicated that 76% of all isolates (from cluster IV) corresponded to a single epidemic strain. Of the 47 strains from one hospital, 41 belonged to cluster IV and were disseminated in three main wards. CTX-M-producing E. coli strains are currently a problem in Portugal, with CTX-M-15 particularly common. This study suggests that the horizontal transfer of bla CTX-M genes, mediated by plasmids and/or mobile elements, contributes to the dissemination of CTX-M enzymes to community and hospital environments. The use of extended-spectrum cephalosporins, quinolones, and aminoglycosides is compromised, leaving carbapenems as the therapeutic option for severe infections caused by ESBL producers.
Occurrence of CTX-M-I Type β-lactamases Gene in Certain Gram Negative Bacteria
ABSTRACT: BACKGROUND: The CTX-M-type β-lactamases represent a group with a typical extended-spectrum β-lactamase (ESBL)-resistance phenotype. These enzymes, encoded by transferable plasmids. They have a preferential hydrolysis of Cefotaxime over Ceftazidime. The CTX-M-type β-lactamases have been described in species of Enterobacteriaceae and Pseudomonas aeruginosa. OBJECTIVE : This study was designed to investigate of the occurrence of CTX-M-I type in some Gram negative bacteria species isolated from clinical cases of in Iraq. METHODS: A group of Gram negative bacteria were isolated from different sources.Plasmid DNA extraction, and electrophoresis were performed. Using specific primers, CTX-M-I enzyme genes were amplified by PCR. RESULTS: Plasmid profile of the tested isolates reveals the presence of relatively large plasmids, their Wight was more than 10 kb some isolates posses’ 3-4 kb plasmids. The results of PCR amplification showed the presence of CTX-I genes. All isolates of Salmonella enterica serovar Typhimurium (100%) are negative for CTX-M-I gene as well as most of P. aeruginosa isolates (86.7%). In contrast, all of E. coli (100%) and most of Proteus Spp isolates were positive for CTX-M-I gene. CONCLUSION: CTX-M genes are predominant in E.coli followed by Proteus Spp. while Salmonella enterica serovar Typhimurium and P. aeruginosa isolates showed low incidence of blaCTX-M genes occurrence. The alarming situation with dissemination of CTX-M producing isolates highlights the need for their epidemiological monitoring and prudent use of antimicrobial agents.
2006
Replicon typing of plasmids carrying bla CTX-M or bla CMY -lactamase genes indicates a predominance of I1 and A/C replicons among bla CMY-carrying plasmids and five different plasmid scaffolds associated with the different types of bla CTX-M genes (I1, FII, HI2, K, and N). These results demonstrate the association of certain -lactamase genes with specific plasmid backbones. Understanding the molecular epidemiology of resistance plasmids has proven to be a complex task due to the diversity and promiscuity of these elements. The relatedness of plasmids can be demonstrated either by restriction fragment pattern analysis or by classification into incompatibility groups (Inc) and replicon (rep) typing (8). These analyses require laborious hands-on work, multiple conjugation or transformation assays, or hybridization experiments (8). A PCR-based replicon typing (PBRT) method has been recently developed and can be easily applied to a larger number of strains (6). The aim of this work was to investigate phylogenetic relatedness among plasmids carrying extended-spectrum cephalosporin (ESC) resistance that are emerging in the United Kingdom and tracing, by PBRT, the diffusion of prevalent plasmids in association with specific ESC resistance gene variants. The PBRT was applied to transformants or transconjugants obtained from 29 Salmonella enterica and 38 Escherichia coli isolates, representing a collection of plasmid-mediated CTX-M or AmpC producers isolated in the United Kingdom between 1995 and 2003. Strains were received from different laboratories in the country or were isolated at the Health Protection Agency Centre for Infections, London, United Kingdom, or at the Veterinary Laboratory Agency, Addlestone, Surrey, United Kingdom, and archived with antimicrobial susceptibility tests, -lactamase gene identification, pulsed-field gel electrophoresis (PFGE), and plasmid profiling, as previously described (1, 2, 3, 10, 11). These strains were not repetitive (one from each patient), and only one strain for each cluster (100% identity by PFGE) was included in the study. Sixty strains were isolated from human urine, blood, feces, sputum, and surgical wounds, and seven strains were from animals (poultry, turkey, horse, and cattle). The ESC resistance genes in this collection were the following: bla CTX-M-9 , bla CTX-M-15 , bla CTX-M-2 , bla CTX-M
Antimicrobial Agents and Chemotherapy, 2007
Of the 181 unduplicated Escherichia coli strains isolated in nine different hospitals in three Portuguese regions, 119 were extended-spectrum β-lactamase (ESBL)-CTX-M producers and were selected for phenotype and genotype characterization. CTX-M producer strains were prevalent among community-acquired infections (56%), urinary tract infections (76%), and patients ≥60 years old (76%). In MIC tests, all strains were resistant to cefotaxime, 92% were resistant to ceftazidime, 93% were resistant to quinolones, 89% were resistant to aminoglycoside, and 26% were resistant to trimethoprim-sulfamethoxazole; all strains were sensitive to carbapenems, and 92% of the strains had a multidrug resistance phenotype. Molecular methods identified 109 isolates harboring a bla CTX-M-15 gene, 1 harboring the bla CTX-M-32 gene (first identification in the country), and 9 harboring the bla CTX-M-14 gene. All isolates presented the IS Ecp1 element upstream from the bla CTX-M genes; one presented the IS 90...
Journal of Antimicrobial Chemotherapy, 2004
ence Laboratory began to receive isolates of Escherichia coli for confirmation of extended-spectrum b-lactamase production with a phenotype implying a CTX-M-type b-lactamase, i.e. MICs of cefotaxime > _ 8-fold higher than MICs of ceftazidime. Many were referred as being from community patients. We examined 291 CTX-M-producing isolates from the UK and investigated the genetic basis of their phenotype.
Journal of Clinical Microbiology, 2004
Organisms producing CTX-M--lactamases are emerging around the world as a source of resistance to oxyiminocephalosporins such as cefotaxime (CTX). However, the laboratory detection of these strains is not well defined. In this study, a molecular detection assay for the identification of CTX-M--lactamase genes was developed and used to investigate the prevalence of these enzymes among clinical isolates of Escherichia coli and Klebsiella species in the Calgary Health Region during 2000 to 2002. In addition, National Committee for Clinical Laboratory Standards (NCCLS) recommendations were evaluated for the ability to detect isolates with CTX-M extended-spectrum -lactamases (ESBLs). The PCR assay consisted of four primer sets and demonstrated 100% specificity and sensitivity for detecting different groups of CTX-M--lactamases in control strains producing well-characterized ESBLs. Using these primer sets, 175 clinical strains producing ESBLs were examined for the presence of CTX-M enzymes; 24 (14%) were positive for bla CTX-M-1-like genes, 95 (54%) were positive for bla CTX-M-14-like genes, and the remaining 56 (32%) were negative for bla CTX-M genes. Following the NCCLS recommendations for ESBL testing, all of the control and clinical strains were detected when screened with cefpodoxime and when both cefotaxime and ceftazidime with clavulanate were used as confirmation tests.