Prevalence and Antimicrobial Resistance of Escherichia coli, Enterococcus spp. and the Major Foodborne Pathogens in Calves in Latvia.

The aim of the present study was to detect the prevalence and antimicrobial resistance of fecal indicators and major foodborne pathogens in feces of calves and to identify the factors associated with increased prevalence of resistant bacteria on farms. Altogether, 180 rectal swabs were collected from 18 farms in Latvia. Samples were investigated to detect the prevalence and antimicrobial resistance of Escherichia coli, Enterococcus spp., Listeria monocytogenes, Yersinia enterocolitica, Salmonella spp., Staphylococcus aureus, and Campylobacter spp. Among all, 64% (74/110) of commensal E. coli, 100% (78/78) Enterococcus faecalis and 96% (22/23) Enterococcus faecium isolates were resistant at least to one antibiotic. The prevalence of extended-spectrum β-lactamase (ESBL)/AmpC-producing E. coli were 11.1% (20/180) with blaCTX-M, blaTEM, and blaCMY genes identified. Campylobacter jejuni (12.8%, 23/180) and Campylobacter coli (2.8%, 5/180) were the most resistant to tetracycline (61%, 14/23; 100%, 5/5) and fluoroquinolones (61%, 14/23; 100%, 5/5). Prevalence of L. monocytogenes was 0.6% (1/180) and S. aureus 1.7% (3/180). All samples were Salmonella and Y. enterocolitica negative. Farm size, bought calves, contact with other calves, and antimicrobial treatment of cows were associated with increased prevalence of resistant E. coli and Enterococcus spp. Despite the low overall usage of antimicrobials in Latvia, the high rates of antimicrobial resistance in fecal indicators and Campylobacter, in addition to the high prevalence of ESBL-producing E. coli, highlights the necessity for the prudent use of antimicrobials in dairy farms in Latvia.