title: Phenotypic and genotypic characterization of antimicrobial resistance in enterohemorrhagic Escherichia coli and atypical enteropathogenic E. coli strains from ruminants.
abstract: Two hundred and twenty-six attaching and effacing Escherichia coli (AEEC) strains (20 enterohemorrhagic E. coli and 206 atypical enteropathogenic E. coli) isolated from calves, lambs, and goat kids with diarrhea and from healthy cattle, sheep, and goats were tested for their resistance to 10 antimicrobial agents by the disc diffusion method. Resistant and intermediate strains were analyzed by polymerase chain reaction for the presence of the major resistance genes. The overall percentage of resistant strains to tetracycline, streptomycin, erythromycin, and sulfamethoxazole was very high (>65%). Moreover, a high level of resistance (approximately 30%) to ampicillin, chloramphenicol, trimethoprim, and trimethoprim-sulfamethoxazole was also detected. The AEEC strains were very susceptible (>90%) to gentamicin and colistin. Because AEEC from ruminants can cause diseases in human beings, the high frequency of antimicrobial resistance detected in the current study is a source of concern. For each antimicrobial agent, the predominant resistance genes in the resistant strains were ampicillin, bla(TEM) (97.1%); tetracycline, tetA (76.7%); gentamicin, aac(3)II (80%); streptomycin, strA/strB (76.7%) and aadA (71.7%); chloramphenicol, catI (85.1%); trimethoprim, dhfrI (76.3%); and sulfamethoxazole, sul1 (60%) and sul2 (63.3%). In the majority of cases, resistance to a given antimicrobial, except for streptomycin, was caused by a single gene. A negative association between tetA and tetB, between aac(3)II and aac(3)IV, and between dhfrI and dhfrV was observed. The present study gives baseline data on frequency and molecular basis of antimicrobial resistance in AEEC strains from ruminants.
authors.affiliation: Departamento de Sanidad Animal, Facultad de Veterinaria, Universidad Complutense, 28040 Madrid, Spain.
authors.forename: Alberto
authors.initials: A
authors.lastname: Medina
authors.forename: Pilar
authors.initials: P
authors.lastname: Horcajo
authors.forename: Sonia
authors.initials: S
authors.lastname: Jurado
authors.forename: Ricardo
authors.initials: R
authors.lastname: De la Fuente
authors.forename: José A
authors.initials: JA
authors.lastname: Ruiz-Santa-Quiteria
authors.forename: Gustavo
authors.initials: G
authors.lastname: Domínguez-Bernal
authors.forename: José A
authors.initials: JA
authors.lastname: Orden
mesh_terms: D000818:Animals; D000900:Anti-Bacterial Agents / Q000494:pharmacology / Q000627:therapeutic use; D002417:Cattle; D002418:Cattle Diseases / Q000188:drug therapy / Q000382:microbiology*; D004269:DNA, Bacterial / Q000737:chemistry / Q000235:genetics; D024901:Drug Resistance, Multiple, Bacterial; D054324:Enterohemorrhagic Escherichia coli / Q000187:drug effects* / Q000235:genetics / Q000378:metabolism; D054308:Enteropathogenic Escherichia coli / Q000187:drug effects* / Q000235:genetics / Q000378:metabolism; D004927:Escherichia coli Infections / Q000188:drug therapy / Q000382:microbiology / Q000662:veterinary*; D015511:Goat Diseases / Q000188:drug therapy / Q000382:microbiology*; D006041:Goats; D008826:Microbial Sensitivity Tests / Q000662:veterinary; D016133:Polymerase Chain Reaction / Q000662:veterinary; D012756:Sheep; D012757:Sheep Diseases / Q000188:drug therapy / Q000382:microbiology*
chemical_list: D000900:Anti-Bacterial Agents; D004269:DNA, Bacterial