Bovine mastitis has a high morbidity rate and causes significant economic losses due to milk wastage and antimicrobial use. Mastitis is treated with antimicrobial agents, but criteria for disk diffusion tests for pathogens that cause bovine mastitis in Japan are lacking. In this study, we used a simplified agar disk diffusion (ADD) method that is easy to implement in clinical practice to develop breakpoints for bovine mastitis–associated organisms and generate a corresponding antibiogram. We established new breakpoints for a simplified ADD method for Staphylococcus aureus, coagulase-negative Staphylococcus (CNS), Streptococcus uberis, Streptococcus spp. (except for S. uberis), and Klebsiella spp. We also revalidated previously reported breakpoints against Streptococcus spp. and E. coli. The antibiogram showed that the susceptibility rates of Streptococcus spp. (excluding S. uberis) to marbofloxacin in eastern Japan were significantly lower than those in Hokkaido and western Japan (P < 0.01). The susceptibility rate of E. coli to oxytetracycline (OTC) in eastern Japan was significantly lower than that in Hokkaido (P < 0.01). Low susceptibility rates were observed for ampicillin (ABPC) and erythromycin among CNS strains, OTC among S. uberis strains, and cefazolin, cefuroxime, and ABPC among Klebsiella spp. strains. The use of breakpoints in the simplified ADD method in clinical practice should promote the prudent use of antimicrobial agents. In cases of acute mastitis with systemic symptoms in which antimicrobial agents must be administered prior to susceptibility testing, the antibiogram can be used as a criterion for determining the drug of choice.

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Classical swine fever (CSF) is an important viral disease of pigs caused by classical swine fever virus (CSFV), with major impacts on animal health and the livestock industry. This study aimed to estimate the seroprevalence of CSFV antibodies in pigs in Bali, assess potential risk factors associated with seropositivity, and describe pathological changes in clinically suspected cases confirmed by rRT-PCR. From September to December 2023, 470 blood samples from pigs with no available vaccination records were collected across Bali and tested using C-ELISA. In addition, 15 pigs showing CSF signs were necropsied for pathological and rRT-PCR evaluation. Six were confirmed CSFV-positive. The overall seroprevalence was 40.8% (192/470, 95% CI: 36.4–45.4). The highest prevalence occurred in Klungkung regency (65.4%, 17/26). Pigs from urban areas were 1.76 times more likely to be seropositive (OR: 1.76, 95% CI: 1.18–2.64) than those from rural areas. By age, pigs under two years were 1.21 times more likely to be seropositive (OR: 1.21, 95% CI: 0.65–2.23), while crossbred pigs were 1.27 times more likely (OR: 1.27, 95% CI: 0.85–1.88) compared to purebreds; however, these differences were not statistically significant. Only location (urban vs. rural) showed a significant association. Pathological changes were observed in the skin, brain, trachea, lungs, kidney, spleen, and intestines. This study demonstrates a relatively high seroprevalence of CSFV in Bali. The limited vaccination records suggests minimal vaccine coverage, indicating that the high seroprevalence most likely reflects natural infection.

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As Johne's disease progresses, clumps of Mycobacterium avium subsp. paratuberculosis (MAP) are identified in the feces. MAP shows resistance to disinfectants, and effective disinfection methods for MAP cells excreted in feces have not been verified. Furthermore, given that biofilm-like vesicles and spore-like morphotypes were observed in feces from infected cattle, we aimed to compare reduction rates between cultured and naturally infected MAP cells after disinfectant treatment. Although the logarithmic reduction value for all cultured MAP cells was > 3.0, four of 10 infected MAP cells showed values < 2.0 after dichloroisocyanuric acid treatment. Our findings suggest that materials contaminated with infected cattle feces should be exposed to higher concentrations of disinfectants than those reported to be effective based on cultured cells.

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