Class 1 integrons and their conjugal transfer with and without virulence-associated genes in extra-intestinal and intestinalEscherichia coliof poultry

Abstract

Multiple-drug resistance in enteric bacteria is frequently associated with integrons. To determine whether integrons may play a role in avian pathogenic Escherichia coli, isolates of extra-intestinal (n 0/27) and intestinal (n0/40) E. coli from dead chicks and turkey poults were analysed for the presence of class 1 integrons and of the virulence-associated genes iss, tsh and colV. Eleven extra-intestinal strains possessed a 1.0 kb class 1 integron with a variable region of aadA1 and were resistant to tetracycline. These traits were indicative of the presence of the Tn21 transposon, which was confirmed by polymerase chain reaction. All extra-intestinal strains had the colV, iss and tsh genes, but none of these genes were cotransferred with the 1.0 kb integron when conjugal transferability was tested. The integron content of the intestinal strains showed considerable variability: one or two of four different class 1 integrons, which varied from 1.0 to 2.4 kb in size, were detected in the 11 strains. The aadA7 gene of the 1.0 kb integron, the dfrA1-aadA1 genes of the 1.6 kb integron and the folA-catB3-aadA5 genes of the 2.4 kb integron were identical to those described by other workers. However, the orfIN682-dhfrV-orfD gene cassette arrangement of the 1.5 kb integron of an intestinal strain of serogroup O5 had no similarity to any previously reported integrons. Conjugal transfer of the 1.6 and 2.4 kb integrons was successful, and in a serogroup O33 intestinal E. coli strain the iss gene was apparently cotransferred with a 1.6 kb integron. The 1.0 and 1.5 kb integrons were not transferable. Our data suggest that intestinal E. coli strains of poultry may be a reservoir for emerging multiresistant strains of avian pathogenic E. coli.

Impact of Feed Supplementation with Antimicrobial Agents on Growth Performance of Broiler Chickens,Clostridium perfringensandEnterococcusCounts, and Antibiotic Resistance Phenotypes and Distribution of Antimicrobial Resistance Determinants inEscherichia coliIsolates

“…Integrons are gene expression elements that contribute to the spread of antimicrobial resistance by gene transfer in a variety of enteric bacteria (6,35,42). The presence of integrons in enteric bacteria from poultry has been previously reported (17,37,41). The 41 integron-positive isolates found in our study were all multiresistant.…”

Chronological Study of Antibiotic Resistances and Their Relevant Genes in Korean Avian Pathogenic Escherichia coli Isolates

“…Therefore, the structures and prevalences of gene cassettes differed substantially among E. coli isolates. However, the structures and frequencies of the gene cassettes of APEC isolates from different countries were similar to each other (30,35). The high frequencies of aadA and dfr can be attributed to selection pressures exerted by streptomycin and trimethoprim, and this observation may be attributed to the frequent prophylactic use of streptomycin and trimethoprim in poultry farms.…”

Antimicrobial resistance and class 1 and 2 integrons inEscherichia colifrom meat turkeys in Northern Italy

“…Moreover, a high percentage of isolates was found positive for class 1 and 2 integrons. Although some data on the presence and characterization of integrons in turkey E. coli are available in the literature (Bass et al, 1999;Singh et al, 2005;Nógrády et al, 2006), none of these studies was targeted to ascertain the distribution of these genetic elements in turkey flocks. Therefore, with this study we provide the first data on the presence and the gene cassette content of class 1 and 2 integrons in E. coli isolated from commercial meat turkey flocks.…”