Mycoplasma bovis causes various bovine diseases such as mastitis, pneumonia, arthritis, and otitis media. In this study, to promote effective treatment and the prudent use of antimicrobials, we conducted an antimicrobial susceptibility survey and molecular epidemiological analysis of 37 M. bovis isolates collected from cattle in Niigata Prefecture. All isolates belonged to a genotype group characterized by low susceptibility to 16-membered macrolide and tetracycline-class antimicrobials. In antimicrobial susceptibility testing, all isolates showed low susceptibility to these antimicrobials, four isolates showed low susceptibility to tulathromycin, and nine isolates to fluoroquinolone (FQ) antimicrobials. These results were generally consistent with findings from single nucleotide polymorphism (SNP) analysis associated with reduced antimicrobial susceptibility. Based on these findings, it is conceivable that phenicol-class antimicrobials should be recommended as first-line treatment for beef cattle, and 15-membered macrolides or FQ antimicrobials should be second-line options. SNP analysis was considered to be a useful diagnostic method that makes it possible to rapidly and appropriately select antimicrobials.

At a dairy farm in Yamagata Prefecture, the mammary glands of nine dairy cows were infected with Mycoplasma bovis. The outbreak ended after cows were treated with a susceptible antimicrobial and the cows that continued to be infected with M. bovis after treatment without exhibiting clinical signs were culled. Approximately two years later, multiple cases of M. bovis mastitis occurred, and the results of pulsed-field gel electrophoresis, multilocus sequence typing, minimum inhibitory concentration, and single nucleotide polymorphisms involved in decreased antimicrobial susceptibility suggested that the strain was likely to be of the same origin. Subsequently, all cows newly affected by mastitis were tested for M. bovis, and the outbreak ended in February 2024 after cows were treated with a susceptible antimicrobial and asymptomatic cows were culled. During this period, the mammary glands of 63 dairy cows were infected with M. bovis, and 21 were culled. Furthermore, within 3 months of M. bovis treatment, mastitis caused by various pathogens recurred in 57.1％ of the cows. This was thought to be due to the exhaustion of the host immune response caused by the M. bovis mammary infection.

Antibiotics promote the selection of resistant bacteria and disrupt the gut microbiota. Probiotics may mitigate these effects, but the optimal timing of their use and the optimal combinations of them remain unclear. In this study, healthy suckling calves were administered cefalexin (CEX) and Clostridium butyricum at different time points. The selection of resistant bacteria and changes in the gut microbiota were evaluated using culture-based methods and 16S rRNA amplicon sequencing. The results indicated administration of C. butyricum prior to CEX reduced the isolation rate of cephalosporin-resistant Escherichia coli and alleviated disruptions of the gut microbiota compared to CEX alone. These findings indicate that the administration of probiotics before antimicrobial treatment may suppress the selection of resistant bacteria and help maintain the balance of the gut microbiota in suckling calves.

Authors investigated the improvement of the method for identifying ipomeamarone (IP) in feed, which is essential for the diagnosis of moldy sweet potato poisoning in cattle. The conventional method takes 2-3 days and requires a lot of extraction equipment and complicated procedures. In addition, the method uses chloroform as an extraction solvent, which is hazardous to both humans and the environment. In this study, several steps were eliminated, including feed freeze-drying and purification processes including the acid and alkaline washing of crude extracts. Furthermore, a modified ethyl acetate method (modified EA method) was evaluated, in which ethyl acetate was used instead of chloroform. It was demonstrated that this modified EA method is sufficiently capable of identifying IP and reduced the total processing time to a single day. The required amount of feed sample was reduced to one-fifth of what it had been, and it was possible to substantially reduce the volume of organic solvent used. The modified EA method represents a highly useful approach because it is simpler and faster than the conventional method, does not require special equipment, and contributes to improved safety through the reduction of exposure to organic solvents.

The emergence of antimicrobial-resistant bacteria has become a serious global concern, highlighting the importance of the appropriate and judicious use of antibiotics, even in companion animals. Although antibiotic prophylaxis is widely used to prevent surgical site infections (SSIs) in small animal surgery, evidence supporting its effectiveness, particularly in the postoperative period, remains limited for soft tissue surgery in dogs and cats. The goal of this retrospective study is to evaluate the incidence and risk factors associated with SSIs in dogs and cats that underwent soft tissue surgeries for wounds classified as clean or clean-contaminated at Azabu University Veterinary Teaching Hospital between January 2021 and November 2023 in which postoperative antibiotic prophylaxis was discontinued within 24 hours. A total of 291 cases were included in this study. Surgical site infections occurred in 20 cases (6.9%). Multivariable analysis identified anesthesia duration and intraoperative hypotension as significant contributors to the development of SSIs (GLM, P＝0.002 and 0.010, respectively). These findings suggest that the discontinuation of antibiotic prophylaxis within 24 hours after surgery does not increase the risk of SSIs in clean and clean-contaminated soft tissue surgeries.

Hemodialysis in dogs and cats presents unique technical challenges compared with human dialysis applications. Currently available systems include veterinary-specific dialysis machines and multipurpose blood purification devices originally designed for human use. However, both systems have significant limitations in the treatment of small-animal patients. For example, veterinary dialysis machines cannot achieve dialysate flow rates below 300 ml/min, which results in disproportionately high dialysate flow rates in small animals that may exceed their physiological tolerance. Conversely, multipurpose blood purification devices, while offering greater flow rate flexibility, have excessive priming volumes of 30‐50 ml, which can be excessive in patients with low body weight. In this study, we conducted a preliminary investigation to evaluate the feasibility of hemodialysis in dogs and cats using infusion pumps as an alternative system. The dialysis system was constructed using three infusion pumps, a syringe pump, and a blood and drug warmer. The priming volume of the blood circuit in this system was 19 ml, which was smaller than that of conventional devices, and the flow rate error was within ±5%. Although the return blood temperature fell below 30℃, a reduction in the dialysate flow rate resulted in a controlled decrease in the efficiency of dialysis.