A Longitudinal Study of the Establishment and Proliferation ofEnterococcuson a Dairy Farm

Abstract

Enterococci are Gram-positive, facultative anaerobic cocci. They are found in many environments (including milk and dairy products, vegetables, plants, cereals, and meats). Enterococci are considered commensal organisms, but can also be opportunistic pathogens associated with morbidity and mortality of humans and animals. A longitudinal study of antibiotic resistance of Enterococcus to ampicillin, erythromycin, and tetracycline was conducted on an academic teaching farm. Environmental samples were collected by drag swabs at select locations prior to and after the introduction of livestock. All samples were initially processed and screened with specialized media, and then replica plated on tryptic soy agar containing a predetermined amount of antibiotic. There was some variation in the quantity of bacterial and antibiotic-resistant colonies; however, resistance to tetracycline was extremely high. The increases of too numerous to count populations were not time-dependent and appeared consistently after the placement of cows. There is little information on the prevalence and epidemiology of antibiotic resistance of Enterococci outside of the hospital setting, including on dairy farms. Longitudinal studies are important in providing insight into the dynamics of establishment and proliferation of bacteria and of antibiotic resistance.

Effects of age and pasture type on the concentration and prevalence of tetracycline and macrolide resistant Enterococcus species in beef cow-calf production system

“…(Lebreton et al, 2014;Cho et al, 2020;Agga et al, 2022a;Kaiser et al, 2022) Furthermore, enterococci have been reported from retail beef (Tyson et al, 2018), retail veal meat (Tate et al, 2021), and ground beef (Vikram et al, 2018;Schmidt et al, 2021) suggesting their foodborne implications. Antimicrobial resistance of enterococci have been extensively studied in feedlot cattle (Vikram et al, 2017;Davedow et al, 2020;Murray et al, 2022), dairy cows (Shipp and Dickson, 2012;Abdelfattah et al, 2021), and to a lesser extent in cull cows. (Pandit et al, 2021) However, such studies are rare in beef cow-calf (Agga et al, 2016) and backgrounding operations (Agga et al, 2019).…”