Phenotypic and genotypic characterization of antimicrobial resistance in Escherichia coli O111 isolates

Phenotypic and genotypic characterization of antimicrobial resistance in Escherichia coli O111 isolates

Author Guerra, B. Google Scholar
Junker, E. Google Scholar
Schroeter, A. Google Scholar
Helmuth, R. Google Scholar
Guth, Beatriz E. C Autor UNIFESP Google Scholar
Beutin, L. Google Scholar
Institution Fed Inst Risk Assessment
Universidade Federal de São Paulo (UNIFESP)
Abstract Objectives: the aim of this study was to generate baseline data on the prevalence and molecular basis of antimicrobial resistance in Escherichia coli O111 isolates.Methods: A total of 105 epidemiologically unrelated E. coli O111 isolates from humans and cattle (isolated between 1983 and 2003) were tested for susceptibility to 17 antimicrobial agents by broth microdilution. Resistant isolates were screened by molecular methods for resistance genes, class 1 and 2 integrons and mutations in the quinolone-resistance determining regions.Results: Resistance was found in 76% of the isolates, with a prevalence of 72% for multi resistance. the most prevalent resistances were to streptomycin, sulfamethoxazole and tetracycline (72-68%), followed by spectinomycin, ampicillin and kanamycin/neomycin (39-25%). for each antimicrobial agent, the predominant resistance genes were ampicillin, bla(TEM) (94%); chloramphenicol, catA1(100%); gentamicin, aac(3)-IV and aac(3)-II (50% each); kanamycin, aphA 1 (100%); streptomycin, aadA1-like (66%); sulfamethoxazole, sul1 (59%); tetracycline, tegA) (86%); and trimethoprim, dfrA1-like (83%). Class 1 integrons were found in 41% of the isolates. They carried aadA1, dfrA1-aadA1 and dfrA15-aadA1. A class 2 integron (dfrA1-sat1-aadA1) was found in one isolate. Only three isolates (3%) were resistant to nalidixic acid (reduced susceptibility to ciprofloxacin), with a single mutation in the gyrA gene.Conclusions: E. coli O111 strains exhibit a wide repertoire of genetic elements to sustain antimicrobial pressure. Two specific antimicrobial resistance pheno/genotypes, [STR-SPT]-SUL-TET/aadA1-sul1-tet(A) and STR-SUL-TET-AMP-[KAN-NEO]/strA/B-sul2-tet(A)-bla(TEM)-aphA1, are predominant.
Keywords STEC
molecular epidemiology
resistance genes
resistance determinants
Language English
Date 2006-06-01
Published in Journal of Antimicrobial Chemotherapy. Oxford: Oxford Univ Press, v. 57, n. 6, p. 1210-1214, 2006.
ISSN 0305-7453 (Sherpa/Romeo, impact factor)
Publisher Oxford Univ Press
Extent 1210-1214
Access rights Open access Open Access
Type Article
Web of Science ID WOS:000238257900029

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