Mycobacterium Abscessus Smooth and Rough Morphotypes Form Antimicrobial-Tolerant Biofilm Phenotypes but Are Killed by Acetic Acid

has emerged as an important pathogen in people with chronic inflammatory lung diseases such as cystic fibrosis, and recent reports suggest that it may be transmissible by fomites. exhibits two major colony morphology variants: a smooth morphotype ( ) and a rough morphotype ( ). Biofilm formation, prolonged intracellular survival, and colony variant diversity can each contribute to the persistence of and other bacterial pathogens in chronic pulmonary diseases. A prevailing paradigm of chronic infection is that is a noninvasive, biofilm-forming, persistent phenotype and an invasive phenotype that is unable to form biofilms. We show that is hyperaggregative and forms biofilm-like aggregates, which, like biofilm aggregates, are significantly more tolerant than planktonic variants to acidic pHs, hydrogen peroxide (HO), and treatment with amikacin or azithromycin. We further show that both variants are recalcitrant to antibiotic treatment inside human macrophage-like cells and that is more refractory than to azithromycin. Our results indicate that biofilm-like aggregation and protracted intracellular survival may each contribute to the persistence of this problematic pathogen in the face of antimicrobial agents regardless of morphotype. Biofilms of each variant are rapidly killed, however, by acetic acid, which may help to prevent local fomite transmission.