Mutant prevention concentration: a new tool for choosing treatment in nontuberculous mycobacterial infections

The mutant prevention concentration (MPC) of fluoroquinolones, linezolid, rifabutin, rifampicin and macrolides was determined in 16 nontuberculous Mycobacterium species in order to compare the incidence of resistant mutant occurrence for different antibiotics. Linezolid showed good activity against Mycobacterium gordonae and Mycobacterium kansasii. Rifabutin had a lower MPC values than rifampicin. The fluoroquinolones were more active against M. gordonae and Mycobacterium chelonae. Clarithromycin had better MPC values than azithromycin but its intracellular concentration was high. Mutant prevention concentration may help to establish a better clinico-microbiological correlation, the sub-populations of drug-resistant micro-organisms may be detected by that method. It is still important to administer correct drug doses, to use combined therapies and to find new drugs that are useful in the treatment of these infections.