Mycobacterium avium biofilms: mechanism of production, composition, and its role in pathogenesis and drug resistance.

The genus Mycobacterium contains over 180 species, and new species are added frequently. Among these are several obligate pathogens, namely Mycobacterium leprae and the species of the Mycobacterium tuberculosis complex; however, the vast majority are environmental bacteria that occupy numerous habitats and are collectively referred to as nontuberculous mycobacteria (NTM). Most NTM are harmless to humans, but the ability of some species to cause infections in people has been increasingly recognized over the past several decades. Mycobacterium avium subs. hominissuis has emerged as one of the most common opportunistic pathogens, usually causing pulmonary infections in susceptible people following environmental exposure. Mycobacterium avium's ability to form biofilms is key to its survival in environments that place it in close proximity to susceptible populations. Their capacity to form biofilms in vivo may also be an important aspect of their pathogenesis and known antibiotic resistance. In this review, we discuss the pathogenesis of this important mycobacterial species, what we know of its ability to form biofilms in vitro and in vivo, and gaps in our knowledge of these processes. We also discuss how we may leverage our understanding of molecules involved in biofilm formation and biofilm matrix composition to develop new therapeutics targeting biofilm formation.