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Incidence and characterization of integrons, genetic elements mediating multiple-drug resistance, in avian Escherichia coli.

ABSTRACT: Antibiotic resistance among avian bacterial isolates is common and is of great concern to the poultry industry. Approximately 36% (n = 100) of avian, pathogenic Escherichia coli isolates obtained from diseased poultry exhibited multiple-antibiotic resistance to tetracycline, oxytetracycline, streptomycin, sulfonamides, and gentamicin. Clinical avian E. coli isolates were further screened for the presence of markers for class 1 integrons, the integron recombinase intI1 and the quaternary ammonium resistance gene qacEDelta1, in order to determine the contribution of integrons to the observed multiple-antibiotic resistance phenotypes. Sixty-three percent of the clinical isolates were positive for the class 1 integron markers intI1 and qacEDelta1. PCR analysis with the conserved class 1 integron primers yielded amplicons of approximately 1 kb from E. coli isolates positive for intI1 and qacEDelta1. These PCR amplicons contained the spectinomycin-streptomycin resistance gene aadA1. Further characterization of the identified integrons revealed that many were part of the transposon Tn21, a genetic element that encodes both antibiotic resistance and heavy-metal resistance to mercuric compounds. Fifty percent of the clinical isolates positive for the integron marker gene intI1 as well as for the qacEDelta1 and aadA1 cassettes also contained the mercury reductase gene merA. The correlation between the presence of the merA gene with that of the integrase and antibiotic resistance genes suggests that these integrons are located in Tn21. The presence of these elements among avian E. coli isolates of diverse genetic makeup as well as in Salmonella suggests the mobility of Tn21 among pathogens in humans as well as poultry.

SUBMITTER: Bass L

PROVIDER: S-EPMC89589 | biostudies-literature | 1999 Dec

REPOSITORIES: biostudies-literature

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Incidence and characterization of integrons, genetic elements mediating multiple-drug resistance, in avian Escherichia coli.

Bass L L Liebert C A CA Lee M D MD Summers A O AO White D G DG Thayer S G SG Maurer J J JJ

Antimicrobial agents and chemotherapy 19991201 12

Antibiotic resistance among avian bacterial isolates is common and is of great concern to the poultry industry. Approximately 36% (n = 100) of avian, pathogenic Escherichia coli isolates obtained from diseased poultry exhibited multiple-antibiotic resistance to tetracycline, oxytetracycline, streptomycin, sulfonamides, and gentamicin. Clinical avian E. coli isolates were further screened for the presence of markers for class 1 integrons, the integron recombinase intI1 and the quaternary ammonium ...[more]

PMID: 10582884

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Project description:Globally, urban water bodies have emerged as an environmental reservoir of antimicrobial resistance (AMR) genes because resistant bacteria residing here might easily disseminate these traits to other waterborne pathogens. In the present study, we have investigated the AMR phenotypes, prevalent plasmid-mediated AMR genes, and integrons in commensal strains of Escherichia coli, the predominant fecal indicator bacteria isolated from a major urban river of northern India Yamuna. The genetic environment of bla CTX-M-15 was also investigated. Our results indicated that 57.5% of the E. coli strains were resistant to at least two antibiotic classes and 20% strains were multidrug resistant, i.e., resistant to three or more antibiotic classes. The multiple antibiotic resistance index of about one-third of the E. coli strains was quite high (>0.2), reflecting high contamination of river Yamuna with antibiotics. With regard to plasmid-mediated AMR genes, bla TEM-1 was present in 95% of the strains, followed by qnrS1 and armA (17% each), bla CTX-M-15 (15%), strA-strB (12%), and tetA (7%). Contrary to the earlier reports where bla CTX-M-15 was mostly associated with pathogenic phylogroup B2, our study revealed that the CTX-M-15 type extended-spectrum ?-lactamases (ESBLs) were present in the commensal phylogroups A and B1, also. The genetic organization of bla CTX-M-15 was similar to that reported for E. coli, isolated from other parts of the world; and ISEcp1 was present upstream of bla CTX-M-15. The integrons of classes 2 and 3 were absent, but class 1 integron gene intI1 was present in 75% of the isolates, denoting its high prevalence in E. coli of river Yamuna. These evidences indicate that due to high prevalence of plasmid-mediated AMR genes and intI1, commensal E. coli can become vehicles for widespread dissemination of AMR in the environment. Thus, regular surveillance and management of urban rivers is necessary to curtail the spread of AMR and associated health risks.

Dataset Information

Incidence and characterization of integrons, genetic elements mediating multiple-drug resistance, in avian Escherichia coli.

Publications

Incidence and characterization of integrons, genetic elements mediating multiple-drug resistance, in avian Escherichia coli.

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