Non-pigmented rapidly growing mycobacteria (NPRGM) are widely distributed in water, soil and animals. It has been
observed an increasing importance of NPRGM related-infections, particularly due to the high antimicrobial resistance.
NPRGM have rough and smooth colony phenotypes, and several studies have showed that rough colony variants are more
virulent than smooth ones. However, other studies have failed to validate this observation. In this study, we have performed
two models, in vitro and in vivo, in order to assess the different pathogenicity of these two phenotypes. We used collection
and clinical strains of Mycobacterium abscessus, Mycobacterium fortuitum and Mycobacterium chelonae. On the in vitro model
(macrophages), phagocytosis was higher for M. abscessus and M. fortuitum rough colony variant strains when compared to
smooth colony variants. However, we did not find differences with colonial variants of M. chelonae. Survival of Galleria
mellonella larvae in the experimental model was lower for M. abscessus and M. fortuitum rough colony variants when
compared with larvae infected with smooth colony variants. We did not find differences in larvae infected with M. chelonae.
Results of our in vivo study correlated well with the experimental model. This fact could have implications on the
interpretation of the clinical significance of the NPRGM isolate colonial variants.