Determination of the in vitro susceptibility of 220 Mycobacterium fortuitum isolates to ten antimicrobial agents

The authors investigated the in vitro susceptibility to antimicrobial agents of 220 Mycobacterium fortuitum isolates originating from clinical samples (14) of patients attending the Hospital Universitario de Canarias and Hospital del Tórax, and from environmental sources (206): 3 from sea water, 10 from the water supply and 193 from sewage. The Minimum Inhibitory Concentration (MIC) was calculated using the broth microdilution method with Mueller-Hinton Broth without supplement. Amikacin was the most efficacious antimicrobial agent against all the isolates of M. fortuitum with an MIC which was considerably lower than its critical concentration. The good results achieved with amikacin in vitro are confirmed by those obtained in vivo, with patients infected with M. fortuitum. No significant difference was found in the efficacy of amikacin and ofloxacin against all the isolates assayed.