Characterisation of an unusual class 1 integron in Escherichia coli isolates of animal origin

Abstract number: P2018

Sáenz Y., Costa D., Vinué L., Somalo S., Ruiz E., Ruiz-Larrea F., Zarazaga M., Torres C.

Objective: To characterize the gene cassette arrangement inside an unusual class 1 integrons that lack the 3'-conserved region, detected in Escherichia coli isolates of animal origin.

Methods: In a prevalence study of class 1 integrons in cotrimoxazole-resistant E. coli isolates of animal origin, two strains (Co125 and C1188) harbouring an unusual class 1 integron that lacked the qacED1 and sul1 genes on the integron 3'-conserved region, were detected. The Co125 and C1188 strains were obtained from faecal samples of a pig and a dog, respectively. The antimicrobial resistance phenotypes were determined by disk diffusion method and the presence of antibiotic resistance genes was analysed by PCR, and sequencing. Based on the known integron sequences previously included in GenBank (accession numbers EF051037 and EF113389), a wide variety of primers were designed to determine the genetic structure of their class 1 integrons, using the PCR and sequencing primer-walking strategy, and the PCR-RFLP analysis with different restriction enzymes.

Results: The E. coli Co125 showed a multiple-antibiotic-resistant phenotype (resistant to nalidixic acid, ciprofloxacin, ampicillin, rifampin, tetracycline, chloramphenicol, sulfamethoxazole, trimethoprim, and streptomycin), and the E. coli C1188 was resistant to tetracycline, chloramphenicol, sulfamethoxazole, trimethoprim, and streptomycin. The tetA, cmlA, sul3, dfrA12, aadA1 and aadA2 genes were found in both strains, and additionally, the blaTEM1b and dfrA1-like genes were detected in the Co125 strain. The same gene cassette combination associated to the sul3-domain was observed in the unusual integron of both strains, which included in the 7.1 kb sequenced fragment downstream the intI1 gene, the following arrangement: dfrA12-orfF-aadA2-cmlA1-aadA1-qacH-IS440-sul3.

Conclusions: To our knowledge this is the first report of multiresistant unusual class 1 integron structure in E. coli isolates of animal origin. The inclusion of a variety of resistance genes inside integrons constitutes an effective means to spread multiple antibiotic resistance among bacteria from different ecosystems.

Session Details

Date: 19/04/2008
Time: 00:00-00:00
Session name: 18th European Congress of Clinical Microbiology and Infectious Diseases
Location: Barcelona, Spain
Presentation type:
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