The Mce proteins do not seem to be involved in cell invasion in the saprophytic strain Mycobacterium smegmatis.

LAURA KLEPP; FEDERICO BLANCO; MARÍA VERÓNICA BIANCO; MARÍA DE LA PAZ SANTANGELO; ANGEL CATALDI; FABIANA BIGI

Rosario, Santa Fe.

Congreso; IVta Reunión de la Sociedad Latinoamericana de Tuberculosis y otras Micobacterias (SLAMTB).; 2009

SLAMTB

Entry into the host cells is one of the primary steps in pathogenesis and mce operons have been reported to participate in the entry of Mycobacterium tuberculosis into mammalian cells (Arruda et al. 1993). However, the presence of these operons was reported not only in pathogenic mycobacteria, but also in Mycobacterium smegmatis, which is generally a saprophyte (Haile et al. 2002). Thus, it is reasonable to think that these operons are implicated in the capacity of this strain to enter mammalian cells, as well. To test this hypothesis we first constructed an M. smegmatis mutant strain with its six mce operons deleted. Then Hella cells were infected at a multiplicity of infection of 10 with the wild type strain and the sextuple mutant. At 1 hour post-infection, the cells were scraped and lysed. Finally, serial dilutions in PBS of the recovered intracellular-bacteria were plated to count colony-forming units (CFUs). No significant differences were observed in the CFUs between the wild type and the sextuple mce mutant strain. From these results we can conclude that the mce operons are not implicated in invasion in the non- pathogenic strain M. smegmatis, at least in the conditions tested here.