Changes in udder health and antibiotic resistance of mastitis pathogens isolated from dairies upon conversion from conventional to organic management over a 3-year period was studied. Coagulase-negative staphylococci (CNS) were the most prevalent mastitis pathogens isolated. CNS were significantly less resistant to beta-lactam antibiotics when isolated from milk after the herd transitioned to organic management. Cessation of the use of antimicrobial therapies in dairies in combination with organic management could lead to a reduction in the antimicrobial resistance of mastitis pathogens.
Ampicillin/pharmacology ; Animals ; Anti-Bacterial Agents/pharmacology ; Cattle ; Cephalothin/pharmacology ; Cloxacillin/pharmacology ; Drug Resistance, Microbial ; Female ; Lactation ; Mastitis, Bovine/*microbiology ; Microbial Sensitivity Tests ; Organic Agriculture ; Penicillins/pharmacology ; Prevalence ; Staphylococcal Infections/microbiology/*veterinary ; Staphylococcus/*drug effects/*isolation & purification