Assessing the Effect of Oxytetracycline on the Selection of Resistant <i>Escherichia coli</i> in Treated and Untreated Broiler Chickens
Ekaterina Pokrant,
María Belén Vargas,
María José Navarrete,
Karina Yévenes,
Lina Trincado,
Paula Cortés,
Aldo Maddaleno,
Lisette Lapierre,
Javiera Cornejo
Affiliations
Ekaterina Pokrant
Laboratory of Food Safety, Department of Preventive Animal Medicine, Faculty of Veterinary and Animal Sciences, University of Chile, Santiago 8820808, Chile
María Belén Vargas
Laboratory of Food Safety, Department of Preventive Animal Medicine, Faculty of Veterinary and Animal Sciences, University of Chile, Santiago 8820808, Chile
María José Navarrete
Laboratory of Food Safety, Department of Preventive Animal Medicine, Faculty of Veterinary and Animal Sciences, University of Chile, Santiago 8820808, Chile
Karina Yévenes
Laboratory of Food Safety, Department of Preventive Animal Medicine, Faculty of Veterinary and Animal Sciences, University of Chile, Santiago 8820808, Chile
Lina Trincado
Doctorate Program of Forestry, Agriculture, and Veterinary Sciences (DCSAV), University of Chile, Av. Santa Rosa 11315, La Pintana, Santiago 8820808, Chile
Paula Cortés
Laboratory of Veterinary Pharmacology (FARMAVET), Faculty of Veterinary and Animal Sciences, University of Chile, Santiago 8820808, Chile
Aldo Maddaleno
Laboratory of Veterinary Pharmacology (FARMAVET), Faculty of Veterinary and Animal Sciences, University of Chile, Santiago 8820808, Chile
Lisette Lapierre
Laboratory of Bacterial Pathogens Diagnostic and Antimicrobial Resistance, Department of Preventive Animal Medicine, Faculty of Veterinary and Animal Sciences, University of Chile, Santiago 8820808, Chile
Javiera Cornejo
Laboratory of Food Safety, Department of Preventive Animal Medicine, Faculty of Veterinary and Animal Sciences, University of Chile, Santiago 8820808, Chile
Oxytetracycline (OTC) is administered in the poultry industry for the treatment of digestive and respiratory diseases. The use of OTC may contribute to the selection of resistant bacteria in the gastrointestinal tract of birds or in the environment. To determine the effect of OTC on the selection of resistant Escherichia coli strains post-treatment, bacteria were isolated from droppings and litter sampled from untreated and treated birds. Bacterial susceptibility to tetracyclines was determined by the Kirby–Bauer test. A total of 187 resistant isolates were analyzed for the presence of tet(A), (B), (C), (D), (E), and (M) genes by PCR. Fifty-four strains were analyzed by PFGE for subtyping. The proportion of tetracycline-resistant E. coli strains isolated was 42.88%. The susceptibility of the strains was treatment-dependent. A high clonal diversity was observed, with the tet(A) gene being the most prevalent, followed by tet(C). Even at therapeutic doses, there is selection pressure on resistant E. coli strains. The most prevalent resistance genes were tet(A) and tet(C), which could suggest that one of the main mechanisms of resistance of E. coli to tetracyclines is through active efflux pumps.