Skin and soft-tissue infections due to rapidly growing mycobacteria: An overview

Rapidly growing mycobacteria (RGM) are increasingly being recognized as potential pathogens. RGM, particularly Mycobacterium abscessus, Mycobacterium fortuitum, and Mycobacterium chelonae, have been observed in both pulmonary and extrapulmonary infections including cutaneous, soft-tissue, and wound infections. However, there are limited reports of these potential pathogens from skin and soft-tissue infections. Moreover, the drug susceptibility profile of RGM is largely unknown in several regions of the world.

We analyzed reports on RGM isolated from skin and soft-tissue infections globally for details of RGM species and drug susceptibility profile. We also analyzed the drug susceptibility profile of four RGM isolates, obtained from skin and soft-tissue infections in our laboratory, by broth microdilution method.

In the reports reviewed, the most common RGM isolated from skin and soft-tissue infections were M. abscessus (184/475, 38.7%), M. fortuitum (150/475, 31.5%), M. chelonae (72/475, 15%), and M. chelonae-M. abscessus complex (46/475, 9.6%). However, drug susceptibility was tested only in 26/39 (66.6%) reports. In our own laboratory, we obtained three isolates of M. abscessus and one isolate of M. fortuitum from one case of breast abscess and three cases of postsurgical wound infections. Maximum susceptibility of M. abscessus was observed to clarithromycin, amikacin, and linezolid. The M. fortuitum isolate was susceptible to clarithromycin, amikacin, clofazimine, and linezolid.

Paucity of information available on RGM isolated from skin and soft-tissue infections highlights the need to be aware of the pathogenic potential and the drug susceptibility profile of these organisms.