Antimicrobial resistance of Salmonella isolates from cattle and horses with salmonellosis in Hokkaido, Japan.

In recent years, reported cases of salmonellosis in cattle and horses in Hokkaido, Japan, have increased. To optimize antimicrobial therapy, we assessed the antimicrobial susceptibility of Salmonella isolates from these animals. Among 112 bovine isolates, high resistance rates were observed for streptomycin (92.0%), ampicillin (88.4%), and tetracycline (79.5%), while resistance rates for kanamycin (8.9%), ciprofloxacin (1.8%), gentamicin (0.0%), and colistin (0.0%) were low. Additionally, 18.8% of the bovine isolates were resistant to cefotaxime, and all of these cefotaxime-resistant isolates carried blaCMY-2. Among 16 equine isolates, no resistance was observed to cefazolin, cefotaxime, gentamicin, nalidixic acid, ciprofloxacin, colistin, or chloramphenicol. Gentamicin and kanamycin are recommended as the first-line treatment for salmonellosis in cattle, with fluoroquinolones as the second choice.