Resistance profile and virulence characterization of Escherichia coli isolated from diarrheic neonatal farm animals

Abstract

Neonatal diarrhea is the main cause of early mortality and morbidity in farm animals and the source of huge, direct and indirect, economic husbandry losses. Escherichia coli, a common harmless commensal bacterium, can turn into a main diarrheal pathogen through antibiotic resistance and the expression of genetically acquired virulence factors. In this study, fecal samples obtained from eight farms of animals with clinical signs characteristic of diarrhea were subjected to culture and bacterial isolation. Colonies suggestive of E. coli were identified through morphological and biochemical characteristics. Susceptibility tests to the main veterinary antibacterial agents were conducted using agar disk diffusion followed by phenotypical detection of extended-spectrum ?-lactamase (ESBL). A total of 301 colonies were characterized as E. coli and, out of the 192 that were tested, 134 showed resistance to three or more classes of antimicrobial drugs and were classified as multidrug resistant (MDR), and 14 were ESBL positive. Bacterial DNA was extracted for multiplex PCR (mPCR) using primers to detect ten different genes of diarrheagenic E. coli (DEC). Thirty-six bacterial strains were positive in the mPCR assay, 28 of which were classified as enterotoxigenic E. coli (ETEC) and eight as enteropathogenic E. coli (EPEC). The high prevalence of MDR strains and the detection of ESBL denote the presence of resistance genes in animal husbandry; thus, it is important to isolate and characterize those pathogens and test antimicrobial sensitivity in vitro to avoid ineffective treatments and the spread of antimicrobial resistance, which are the major concerns of Public Health and One Health.