Class 1 and class 2 integrons in avian pathogenic Escherichia coli from poultry in Italy

Abstract

The aim of this study was to investigate the occurrence of class 1 and 2 integrons in avian pathogenic Escherichia coli (APEC) from poultry in northern Italy. Strains were tested for phenotypic resistance to aminoglycosides and sulphonamides, and the association between the presence of integrons and the resistance to these antimicrobials was evaluated. A total of 299 isolates (158 from turkeys, 110 from broilers, and 31 from layer hens) were collected from 200 industrial farms. Antimicrobial susceptibility test by the disk diffusion method was performed in accordance with the Clinical and Laboratory Standards Institute (CLSI) guidelines. All strains were screened for the presence of class 1 and 2 integrons by PCR and sequencing. About 55% of APEC contained integrons (class 1, 49.8%; class 2, 10.4%). Different variants of the aadA (5 variants) and the dfrA (4 variants) genes, encoding for streptomycin and trimethoprim resistance respectively, were detected in integron-positive isolates. Less common gene cassettes, such as sat, estX, and orfF, were also identified. Fifteen and 4 gene cassette arrays were found among class 1 and 2 integrons, respectively. High levels of resistance were observed for triple sulphonamides (79.3%), streptomycin (67.2%), and sulfamethoxazole combined with trimethoprim (62.2%), whereas resistance against gentamycin (16.7%), kanamycin (14.7%), and apramycin 3.0%) was low. Integron positivity was significantly higher in isolates phenotypically resistant to aminoglycosides (63.6% vs. 37.8%, P<0.001) and sulfonamides (64.1% vs. 21.1%, P<0.001) than in susceptible ones. Integron-borne aminoglycoside and sulfonamide resistance in APEC represents a concern for the poultry industry in Italy, since they are among the most commonly used antimicrobials in poultry therapy.

Antimicrobial resistance and integron gene cassette arrays in commensal Escherichia coli from human and animal sources in IRI

“…Our molecular results are also comparable to Cavicchio et al because as they reported, the most common gene cassette arrays identified in class I integron-positive isolates belonged to the aadA (90/149 isolates, 60.4 %) and the dfrA (50/149 isolates, 33.6 %) gene families, with 5 and 4 different variants, respectively. However, the prevalence of aadA and dfrA cassette arrays in class II integrons are incompatible to our results, because Cavicchio et al identified aadA and dfrA in 67.7 and 64.5 % of the class II integron positive isolates [23]. …”

“…However, it was also evident that some integron-carrying organisms had reduced susceptibility not only to antimicrobial agents for which the respective gene cassettes were contained in but also to other classes of agents for which no or very little number of genes were contained within the integrons [23]. …”

“…Cavicchio et al isolated 299 E. coli from avian source and found class I and II, in 49.8 and 10.4 % of the samples while thirteen strains (4.3 %) were positive for both classes [23]. Our molecular results are also comparable to Cavicchio et al because as they reported, the most common gene cassette arrays identified in class I integron-positive isolates belonged to the aadA (90/149 isolates, 60.4 %) and the dfrA (50/149 isolates, 33.6 %) gene families, with 5 and 4 different variants, respectively.…”

Studies on avian pathogenic Escherichia coli in commercial broiler chicken in South East Queensland

“…Class 3 integrons have also been reported in E. coli (Deng et al, 2015). Class 1 and 2 integrons have been identified in APEC in poultry worldwide (Awad et al, 2016;Cavicchio et al, 2015;Nogrady et al, 2006). …”

“…They have also been proven to play a role in distribution and spread of AMR (Deng et al, 2015). Several studies have reported a positive association between integrons and multidrug resistant E. coli isolates in food-producing animals (Cavicchio et al, 2015;Dou et al, 2016;Szmolka et al, 2015) as well as in humans (Lavakhamseh et al, 2016).…”