ABSTRACT
Listeria monocytogenes is a model intracellular pathogen which escapes from a host cell vacuole, grows intracytoplasmically, and spreads cell to cell without an extracellular phase. A number of genes necessary for pathogenicity have been discovered, two of which encode phospholipases C, a PI-PLC and a broad-range PLC. Single and double mutants were constructed with in-frame deletions in one or both PLCs. Characterization of the strains indicated that the two PLCs may have overlapping functions as the double mutant was 500-fold less virulent while the single mutants had a negligible effect on virulence. The role of the PLCs appears to be multifactorial as PI-PLC has a role in escaping from the initial host vacuole and the broad-range PLC appears to have a role in cell to cell spreading