Rats as sources of multidrug-resistant Enterobacteriaceae in animal production environments

DOMINGUEZ, JOHANA ; LOVERA, ROSARIO; SANCHEZ, JULIANA P.; REDONDO, LEANDRO ; CHACANA, PABLO ANIBAL ; REGINO CAVIA; FERNÁNDEZ MIYAKAWA, MARIANO ENRIQUE

ZOONOSES AND PUBLIC HEALTH

WILEY-BLACKWELL PUBLISHING, INC

Lugar: Londres; Año: 2023

1863-1959

Rattus norvegicus and Rattus rattus are commensal pest rodents, considered reservoirsand vectors of zoonotic pathogens. In livestock farms, the wide use of antimicrobialsand their release into the environment lead to high long-termresidual concentrations,which may in turn lead to the occurrence of antimicrobial resistance (AMR). Farmenvironments serve as AMR sources, resulting in the transmission of antimicrobial-resistantbacteria and their AMR genes of livestock origin into wildlife. This studyaimed to analyse the profile of enterobacteria carrying AMR determinants in rats capturedin livestock farms to determine their potential vectors as for the spread of AMR.To this end, 56 rats (52 R. norvegicus and 4 R. rattus) were live-trappedon 11 farms(pig, dairy, poultry and mixed farms) located in central Argentina, from spring 2016to autumn 2017. From 50 of the R. norvegicus individuals and three of the R. rattusindividuals found in 10 of the farms, we isolated 53 Escherichia coli and five Salmonellastrains. Susceptibility to antimicrobials, genotypic profiles, minimal inhibitory concentrationof colistin and the presence of mcr-1and genes encoding extended-spectrumβ-lactamase(ESBL) were determined. Of the 58 isolates not susceptible to differentantimicrobial classes, 28 of the E. coli strains and two of the Salmonella strains weredefined as multi-drugresistant (MDR). S. Westhampton and S. Newport recoveredwere not susceptible to ampicillin or all the cephems tested. One of the E. coli obtainedshowed resistance to colistin and harboured the mcr-1gene, demonstratedby PCR and conjugation. In two ESBL-producingSalmonella isolated from rats, CTX-M-2genes were responsible for the observed resistance to third-generationcephalosporins.The MDR E. coli isolates showed several different resistance patterns (23),although some of them were the same in different individuals and different farms,with six resistance patterns, evidencing the dispersion of strains. These findings suggestthat rats play a role in the dissemination of AMR determinants between animal,humans and environmental reservoirs