Antimicrobial use and its association with the presence of methicillin-resistant staphylococci (MRS) and extended-spectrum beta-lactamases (ESBL)-producing coliforms in mastitic milk on dairy farms in the Chiba Prefecture, Japan.

Food-producing animals, including dairy cattle, are potential reservoirs of antimicrobial resistance. However, there is limited data on antimicrobial use and the selection of resistant bacteria. Therefore, we investigated the association between antimicrobial use and resistance to mastitis pathogens using 2016 data from milk samples collected from cows with mastitis in 134 dairy farms in Chiba Prefecture, one of the principal dairy production prefectures in Japan. We recorded the antimicrobial use and isolation of methicillin-resistant staphylococci (MRS) and extended-spectrum beta-lactamase (ESBL)-producing coliforms (E. coli and Klebsiella spp.), and used the antimicrobial treatment incidence (ATI; the theoretical number of animals per 1000 animal-days subjected to antimicrobial treatment) to indicate antimicrobial use on each farm. The farms in which MRS or ESBL-producing coliforms were isolated from at least one mastitic milk sample were classified as antimicrobial resistance (AMR)-positive, and those in which neither MRS nor ESBL-producing coliforms were isolated were classified as AMR-negative. The AMR-positive farms showed a significantly higher ATI (median 45.17) than AMR-negative farms (median 38.40). The results indicate that high antimicrobial usage is associated with AMR in staphylococci and coliforms isolated from mastitic milk on dairy farms in Chiba Prefecture.

Changes in the C-reactive protein and 13,14-dihydro-15-keto-prostaglandin F2α concentrations of uterine lavage samples after the administration of povidone-iodine in cows.

Changes in the C-reactive protein (CRP) and 13,14-dihydro-15-keto-prostaglandin F2α (PGFM) concentrations of uterine lavage fluid were examined in cows given an intrauterine povidone-iodine (PI) infusion. The mean polymorphonuclear leukocyte (PMN) ratios (the ratio of PMN to total cells) and CRP concentration of uterine lavage fluid on the day after the treatment were significantly (P<0.05) greater in the PI infusion group (PMN: 53.0 ± 32.7%, CRP: 50.2 ± 32.3 ng/mL) than in the non-treatment control group (PMN: 7.9 ± 21.9%, CRP: 17.2 ± 5.9 ng/mL), whereas there was no significant difference in the mean PGFM concentration between the two groups. The present findings suggest that the uterine CRP level is a useful biomarker of local uterine inflammation in cows.

Evaluating the antimicrobial use on dairy farms in Chiba Prefecture in Japan using the antimicrobial treatment incidence, an indicator based on Japanese defined daily doses from 2014-2016.

The use of antimicrobial agents in food-producing animals may lead to the emergence and spread of antimicrobial resistance in bacteria of animal origin. However, there is a paucity of data on the quantity of antimicrobials use on dairy farms in Japan. This study describes antimicrobial use on dairy farms from 1 January 2014 to 31 December 2016 in five administrative districts (central, eastern, western, southern and northern) of Chiba Prefecture. The use of antimicrobial agents in dairy cattle over these three years was evaluated in terms of the antimicrobial treatment incidence (ATI; theoretical number of animals per 1,000 animal-days subjected to antimicrobial treatment) using data collected from a total of 442 dairy farms in that prefecture. Our results revealed that the average ATI on these farms for these years ranged from 38.7 to 39.4 with no significant difference between years and that the average ATI for these administrative districts varied between 32.9 and 43.2 with a significant variation between some of the districts. Approximately 84% of antimicrobials were administered intramammarily, 13-14% by injection and 1-2% orally. Scenario analyses were performed to assess the effect of changes in some of the defined daily dose (DDDjp) values used to calculate the ATI. Our results revealed that the calculated ATI is considerably affected by the changes in the long-acting factor used for assigning the DDDjp values of intramammary products for dry cows and the way in which DDD values are assigned for combination products.