Antimicrobial susceptibility of Salmonella isolated from cattle, swine and poultry (2001-2002): report from the Japanese Veterinary Antimicrobial Resistance Monitoring Program

Abstract

Objectives: The Japanese Veterinary Antimicrobial Resistance Monitoring (JVARM) Program was established in 1999 to examine the susceptibility of bacteria from food-producing animals to antimicrobial agents. This study tested the susceptibility of Salmonella isolates collected during 2001-2002 to 20 antimicrobials.

Materials and methods: MICs of antimicrobial agents were determined using the NCCLS agar dilution method, and interpreted according to breakpoints obtained from the bimodal MIC distributions.

Results: A total of 82 Salmonella were isolated from food-producing animals and tested for antimicrobial susceptibility. Isolates resistant to ampicillin, dihydrostreptomycin, kanamycin, oxytetracycline, chloramphenicol, bicozamycin, nalidixic acid, oxolinic acid and trimethoprim were obtained from healthy animals and diagnostic sample submissions. Salmonella Dublin was isolated only from cattle and showed resistance to older quinolones. Resistance to ampicillin, dihydrostreptomycin, kanamycin and oxytetracycline was common across all serotypes. Fluoroquinolone-resistant Salmonella Choleraesuis was isolated from swine and was the first Japanese report on this type of resistance in Salmonella from an animal origin. Most Salmonella Typhimurium isolates showed resistance to ampicillin, chloramphenicol, dihydrostreptomycin and oxytetracycline. S. Typhimurium DT104 accounted for 40.7% of S. Typhimurium isolates and was more often multi-drug resistant. Most Salmonella Infantis isolates from poultry showed resistance to dihydrostreptomycin, oxytetracycline, trimethoprim or kanamycin. In Salmonella Enteritidis, the major serotype isolated from food-poisoning in Japan, only resistance to dihydrostreptomycin was observed.

Conclusions: This is the first JVARM report of Salmonella isolates, and continuous investigations at the national level on antimicrobial resistance in Salmonella isolated from food-producing animals will be important in the JVARM Program.