The Graduate School of the University of Tokyo and the Chiba Agricultural Mutual Aid Association conducted research on multidrug resistance in the milk of mastitis-affected cows in dairy farms in Chiba Prefecture, with the aim of addressing drug resistance to antibacterial agents, which has become a global problem in recent years. We clarified the relationship between the occurrence of bacteria (MRS or ESBL-producing coliforms) and the amount of antimicrobial agents used.
Mastitis, also known as a dairy cow production disease, is the most frequent cause of antibiotic use in dairy farming.Staphylococci and coliforms, which are the main causative agents of bovine mastitis, have been reported to have antimicrobial resistance (AMR) in several countries. Some studies have also shown an association withHowever, there were no data indicating the relationship between the amount of antibiotics used and AMR in mastitis-affected milk in Japanese dairy farms.
In 2016, the research group investigated the relationship between antimicrobial resistance (AMR) in bacteria isolated and cultured from milk derived from mastitis-affected cows and the amount of antimicrobial agents used in 134 dairy farms in Chiba Prefecture.Farmers with one or more multidrug-resistant bacteria detected are AMR (+) farms, and farms with no multidrug-resistant bacteria detected are AMR (-) farms, and the amounts of antibacterial agents used (ATI: opportunities to use antibacterial agents per 1 head-days) are compared. As a result, it was found that AMR(+) farmers used more antibacterial agents.
In addition, by route of administration, intramammary injection drugs (for treatment during lactation) and injection drugs, and by antibiotic type, penicillin-, tetracycline-, and sulfonamide-type ATIs were higher in AMR (+) farms than in AMR (-) farms. was significantly higher.
The results of this study indicated the possibility that efforts to suppress the occurrence of mastitis and reduce the amount of antibacterial agents used through prevention and hygiene management could lead to countermeasures against AMR.In the future, we will proceed to identify detailed risk factors, including factors other than the amount of antibacterial agents used, regarding the impact of antibacterial agent use in dairy farming on AMR.
