A national surveillance of antimicrobial resistance in bacteria isolated from domestic animals in Japan

The Japanese Veterinary Antimicrobial Resistance Monitoring System (JVARM) was formed in 1999 in response to international concerns about the impact of antimicrobial resistance on public health. The aim of the present project was to provide insight into the occurrence of antimicrobial resistance among bacterial strains isolated from cattle, swine and poultry across Japan. In this report, we summarize a nationwide investigation (1999-2003) on antimicrobial susceptibility of the targeted bacterial species for the JVARM, namely Salmonella, Campylobacter, Enterococcus and Escherichia coli, isolated from the feces of healthy domestic animals. Minimum inhibitory concentrations (MICs) of 10-18 antimicrobial agents including the major generic groups were determined using an agar dilution method, and interpreted according to breakpoints obtained from the bimodal MIC distributions. The outline of the present results is as follows: (1) A total of 307 Salmonella, 1,120 Campylobacter, 2,822 Enterococcus and 3,225 E. coli were isolated from healthy domestic animals and examined for antimicrobial susceptibility. (2)The isolates of all targeted bacterial species showed high rates of antimicrobial resistance to both oxytetracycline (OTC) and dihydrostreptomycin (DSM). (3) Among the isolates of Campylobacter and E. coli, the frequency of isolation of resistance to fluoroquinolones ranged from 14 to 24% and 2 to 3%, respectively. (4) Resistance to fluoroquinolones was not observed among the isolates of Salmonella or Enterococcus. Continuous investigation at the nation level of antimicrobial resistance among the isolates from healthy domestic animals remains a high priority for the JVARM program. Furthermore, appropriate and prudent use of antimicrobials for diseased animals should be considered essential in the future.