The BCG1619c gene of Mycobacterium bovis bacillus Calmette-Guérin (BCG) encodes for a 24 kDa invasin-like protein and is identical to the Rv1566c gene of Mycobacterium tuberculosis. To assess whether this protein was necessary for entry and (or) intracellular persistence in professional phagocytes and (or) in lung epithelial cells, a BCG1619c knockout mutant of M. bovis BCG was generated and compared with the parental BCG strain for its ability to infect and multiply in human monocyte derived THP-1 cells and in the lung epithelial cell line A549. No significant difference between the mutated and the parental BCG strain was observed in either of these in vitro infection systems, indicating that the BCG1619c gene is not essential for cell invasion and intracellular growth of BCG.