In vitro efficacy of imipenem in combination with six antimicrobial agents against Mycobacterium abscessus

Antimicrobial therapy of Mycobacterium abscessus infection is difficult because there are relatively few effective treatment regimens and single-agent therapy frequently fails clinically. In light of the lack of data on the susceptibility profile of M. abscessus strains recovered from infections in Japan, the in vitro activity of imipenem in combination with clarithromycin, levofloxacin, moxifloxacin, minocycline, amikacin or tobramycin was investigated by the checkerboard method and compared with the combination amikacin and cefoxitin. The combination of imipenem with moxifloxacin, levofloxacin or clarithromycin had a higher synergistic and/or additive effect than amikacin and cefoxitin. A decrease in the MIC₉₀ value (minimum inhibitory concentration for 90% of the organisms) was observed in the presence of imipenem for clarithromycin, minocycline, levofloxacin and moxifloxacin. The data suggest that a combination regimen including imipenem may be a good choice in empirical treatment of M. abscessus infection.