Virulence factor that promotes intracellular proliferation by mediating the disruption of the phagocytic vacuole and the release of bacteria into the host cell cytosol. May act in concert with the phospholipases PlcA and PlcB and the hemolysin hly to mediate efficient escape from the vacuole. a sphingomyelin + H2O = an N-acylsphing-4-enine + H(+) + phosphocholine A knockout mutant was shown to be weakly hemolytic on sheep blood agar, does not produce the external halo of incomplete hemolysis characteristic of L.ivanovii and does not give the typical shovel-shaped cooperative hemolytic 'CAMP-like' reaction that happens with Rhodococcus equi. Is also much less virulent for mice infected intravenously. Complementation with SmcL of a mutant lacking the membrane-damaging determinants hly, PlcA and PlcB (thus unable to grow intracellularly) was sufficient to promote bacterial intracellular proliferation. Belongs to the neutral sphingomyelinase family.