The effect of Enterococcus faecium M74 feed additive on the extended-spectrum beta-lactamases/AmpC-positive Escherichia coli faecal counts in pre-weaned dairy calves

The increasing occurrence of extended-spectrum beta-lactamases and/or AmpC-positive Escherichia coli among different species of food producing animals poses a threat to public health. The animal gut plays a key role in the development of antibiotic resistant bacteria, allowing the selection, multiplication and subsequent contamination of the farm environment. However, applicable procedures for reducing such bacteria on farms are currently unavailable. The present study was aimed to determine whether a probiotic administration to new-born dairy calves would reduce faecal shedding of extended-spectrum beta-lactamases and/or AmpC-positive Escherichia coli during the pre-weaning period. Ten randomly assigned new-born Holstein calves on a dairy farm with recent evidence of high occurrence of AmpC-positive Escherichia coli among calves were treated by a probiotic mix within 12 h after birth. Nine control calves were not treated. Faecal samples were collected from each calf daily on days 2 through 5, and then on days 7, 10, and 14. The faecal samples were cultured, and the mean numbers of cefotaxime-resistant Escherichia coli and confirmed enteroaggregative Escherichia coli were compared between the two groups. Results suggested that the Enterococcus faecium probiotic treatment (Enterococcus faecium M74, NCIMB 11181) of new-born calves did not reduce the enteroaggregative Escherichia coli counts in their faeces. There was no significant difference in the shedding of enteroaggregative Escherichia coli between the probiotic-treated and control calves throughout the two-week study period. Probiotic, antimicrobial resistance, cattle Continued increase in the incidence of antibiotic resistance among agents of infectious diseases of humans and animals represents a common threat to human and veterinary medicine. Along with pathogenic bacteria, antibiotic therapy also applies to commensal species of intestinal microflora, especially Escherichia coli, which can carry and then spread genes of resistance onto pathogenic species. That means that animal gut may play a key role in the development of antibiotic resistant bacteria, allowing the concealed selection, multiplication and subsequent contamination of the farm environment (Carlet 2012). The increasing incidence of extended-spectrum beta-lactamases (ESBL) and/or AmpC-positive Escherichia coli (enteroaggregative E. coli EAEC) in the community of the last decade is also connected with the findings of these bacteria in the food animals and their products (Seiffert et al. 2013). Therefore it seems reasonable to limit the use of antibiotics in farm animals to a minimum and look for procedures leading to the reduction of resistant bacteria on farms. The prevalence of ESBL in faecal swabs of healthy cattle in Europe is 5–13% (Geser et al. 2012; Hartmann et al. 2012). The lowest prevalence of ESBL/AmpC-producing Escherichia coli in Europe is reported in Finland, at 1.8% (Paivarinta et al. 2016). In the Czech Republic, data are available on the phenotypic resistance of Escherichia coli isolates in cattle for years 2015 – 10.7% and 2016 – 10.4% (SVA 2017). Results published so far show that in comparison to adult cattle, calves are relatively often colonized with resistant E. coli, including EAEC, although not treated with antibiotics (Khachatryan et al. 2004; Watson et al. 2012). During the first weeks of milk ACTA VET. BRNO 2017, 86: 333–338; https://doi.org/10.2754/avb201786040333 Address for correspondence: Jana Šmídková Ruminant and Swine Clinic, Faculty of Veterinary Medicine University of Veterinary and Pharmaceutical Sciences Palackého tř. 1946/1, 612 42 Brno, Czech Republic Phone: +420 777 624 044 E-mail: smidkovaj@vfu.cz http://actavet.vfu.cz/ nutrition, the excretion reaches maximum level, and then gradually decreases with age (Khachatryan et al. 2004; Berge et al. 2005; Watson et al. 2012). Influences/factors that are involved in the selection and maintenance of these bacteria on dairy farms were also identified (Gonggrijp et al. 2016). But it is still not clear which extra measures will be effective to further reduce the prevalence of EAEC on dairy farms (Reeves et al. 2013). One of the options how to reduce the incidence of these bacteria on farms could be the induction of intestinal colonization resistance of new-born calves by using probiotics from the group of lactic acid bacteria (Signorini et al. 2012; Pringsulaka et al. 2015) which could reduce the excretion of EAEC in the calves’ faeces. Only sporadic attempts to verify such procedures in order to reduce calf colonization by EAEC (Corbett et al. 2015) have been made so far. The present study was aimed to determine whether a single administration of lactic acid bacteria to new-born dairy calves would reduce the faecal shedding EAEC. Materials and Methods