Domestic and game pigeons as reservoirs for Escherichia coli harboring antimicrobial resistance genes

Abstract Objectives In Iran, pigeons are kept and bred on the roofs of houses which indicate the potential significance of pigeons in the dispersal of antimicrobial resistant E. coli strains. Here we characterized antimicrobial resistance genotypes in relation with phenotypic presentations and phylogenetic backgrounds of the E. coli isolates from household pigeons in Kerman in southeast of Iran. Methods Totally, 152 fecal E. coli isolates from domestic and household pigeons were subjected to screen thirteen antimicrobial resistance genes including blaTEM, blaSHV, blaCTX-M, sulI, sulII, dhfrI, dhfrV, aadA, aac(3)-I, tetA, tetB, floR and qnrA by conventional PCR technique. Clermont phylogenetic background of E. coli strains was studied and antibiotic resistance of all strains was assessed for seven antibiotics. Results The antimicrobial resistance genes including blaTEM, tetA, tetB and aadA were detected in 52.6%, 6.5%, 6.5% and 5.9% of the isolates, respectively. PCR phylo-typing revealed that a significant number of isolates within A0 (54%), A1 (70%), B1 (57.6%), B22 (75%) and D1 (87.5%) phylo-groups were positive for the studied resistance genes. One phenotypic resistance pattern (trimethoprim-sulphamethoxazole) was associated with the presence of the corresponding gene sul2. Conclusions An alarming rate of phenotypic resistance was observed in this study. Many isolates were positive for the screened resistance genes. According to the phylogenetic background, most resistant isolates belonged to the commensal phylo-types, representing significant role of commensal strains as a source of resistance genes. These findings highlight the role of pigeon as disseminator of resistant E. coli strains.