标题：Antimicrobial Susceptibility of 616 Rhodococcus equi Strains Isolated from Tracheobronchial Aspirates of Foals Suffering from Respiratory Disease in Japan
摘要：To obtain basic data for development of a new antimicrobial regimen against R. equi infection in foals, we performed two experiments using antimicrobial susceptibility tests that included disk diffusion tests and Etests. An initial examination of the susceptibility of 8 clinical R. equi isolates to 111 antimicrobial agents revealed that 18 agents in 6 groups performed effectively against all the isolates. We then examined the antimicrobial susceptibility to 6 representative agents of the 18 antimicrobials of 616 R. equi strains isolated from tracheobronchial aspirates of foals with respiratory disease in Japan. There were no resistant strains in these 616 R. equi isolates. However, antimicrobial-resistant mutants, which appeared in the inhibitory zone around antimicrobial disks, were also observed in ciprofloxacin, gentamicin, and rifampin. The minimum inhibitory concentrations of most of the ciprofloxacin-resistant mutants and all of the rifampin-resistant mutants exceeded the break points of both ciprofloxacin and rifampin. Our results suggest that in Japan, there are no strains resistant to the 6 antimicrobial agents, suggesting that the 18 agents in the 6 groups are potential therapeutic agents for new regimens against R. equi infection in foals. Our data also suggests a risk of the development of problematic antimicrobial resistance to ciprofloxacin and rifampin in R. equi .
