CONICET | Buscador de Institutos y Recursos Humanos

Norway rats (Rattus norvegicus) represent a public health problem, since they are reservoirs of several zoonotic pathogens. The presence of Norway rat populations in the study area is associated with animal breeding farms in which rats reproduce all year long because of the continuous availability of food and water. Given the increasing occurrence of Escherichia coli strains resistant to antimicrobials in the farms and the discussion about environmental reservoirs, the purpose of this study was to perform a preliminary screening to determine the dispersion of antibiotic resistance of E. coli isolates recovered from Norway rats on farms from two localities, Marcos Paz and San Andrés de Giles in the province of Buenos Aires.A selected group of 28 isolates of E. coli recovered from Norway rats were examined. Isolates were obtained from cultures of large intestine samples on McConkey agar plates. To determinate the antimicrobial resistance, the Kirby?Bauer disk diffusion susceptibility test was performed according to the CLSI.28.5% E. coli isolates were resistant to multiple drugs (resistance to at least three 3 or more antimicrobial classes). Resistance to ampicillin and cephalothin was higher (46.4% and 42.9%, respectively), while resistance to 3GCs (ceftriaxone) was low (14.3%). Resistance to different antimicrobial families was observed such as tetracycline, nalidixic acid (32%) and streptomycin (28%). Only one isolate showed resistance to colistin. None of the strains showed resistance to imipenem and fosfomycin. The ability of rats to be a potential source of environmental antibiotic resistant pathogens has received little consideration, and their importance of this host as dispersed of these organisms requires further investigation. Thus, the preliminary results of this study shows that rats may act as a source of the dissemination of multi-resistant bacteria and resistance genes from the productive system to the human.