Antibiotic resistance of Escherichia coli isolated from Norway rats (Rattus norvegicus) from farms of Northeast Buenos Aires

DOMÍNGUEZ JOHANA E.; REDONDO LEANDRO M.; LOVERA ROSARIO; BUCCI JESSICA S.; CAVIA REGINO; FERNÁNDEZ MIYAKAWA MARIANO E.

Capital Federal

Encuentro; Reunión Conjunta de Sociedades de Biociencias; 2017

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, Argentina. A selected group of 28 isolates of E. coli recovered from Norway rats caught during November-December 2016 were examined. Isolates were obtained from cultures of large intestine sampleson McConkey agar plates, incubated at 37 ° C for 18 hours. In all cases, the identity of the isolates obtained was confirmed by routine biochemical tests. To determinate the antimicrobial resistance of the isolates, the Kirby?Bauer disk diffusion susceptibility test was performed according to the CLSI using: ampicillin, amoxicillin-clavulanic acid, cephalotin, cefuroxime, ceftriaxone, ceftiofur, cefoxitin, aztreonam, kanamycin, gentamicin, streptomycin, amikacin, tetracycline, chloramphenicol, nalidixic acid, ciprofloxacin, enrofloxacin, imipenem, meropenem , colistin and fosfomycin. Eight of 28 (28.5%) E. coli isolates were resistant to multiple drugs (resistance to at least three 3 ormore antimicrobial classes). Resistance to ampicillin and cephalothin was higher (46.4% and 42.9%, respectively), while resistance to third generation cephalosporins (ceftriaxone) was low (14.3%). On the other hand, resistance to different antimicrobial families was observed such as tetracycline, nalidixic acid (32%) and streptomycin (28%). Only one isolate showed resistance tocolistin. 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 theproductive system to the human.