COMBINATION-DRUG TESTING OF MYCOBACTERIUM-CHELONAE

Purpose. Medical therapy of Mycobacterium chelonae keratitis is diffic ult because there are so few effective antimicrobial agents and single agent therapy frequently fails clinically. To identify more effective medical treatment regimens, the in vitro antimicrobial efficacy of am ikacin, the most frequently used single agent, was investigated in com bination with four antibiotics previously reported to have activity ag ainst M. chelonae: erythromycin, imipenem, ciprofloxacin, and vancomyc in. Methods. The drug combinations were tested by the checkerboard met hod against seven corneal isolates of M. chelonae. Results. The combin ation of amikacin with erythromycin or vancomycin consistently led to synergistic or additive effect, however the minimum inhibitory concent rations for vancomycin were very high. The combination of amikacin wit h imipenem or ciprofloxacin led to results ranging from antagonism to additive effects. Conclusions. Of the antibiotics tested, erythromycin showed the most activity against M. chelonae in combination with amik acin. In vitro combination drug testing of M. chelonae by the checkerb oard method should be further evaluated for clinical relevance in micr obial keratitis.