Production of a New Extracellular Cytotoxin from Listeria monocytogenes Serotype 4b and ATCC 15313 Serotype 1/2a in Relation to Growth Stage and Growth Temperature

Abstract

Both virulent (4b) and avirulent (ATCC 15313:l/2a) strains of Listeria monocytogenes synthesize a previously unrecognized extracellular cytotoxin over a broad temperature range of 4–37°C. The highest level of cytotoxin production was observed during stationary phase; however, for all growth temperatures cytotoxin production was detected in early to mid-log phase. The cytotoxin was stable in the growth medium at both 37 and 4°C. Both strains synthesized the cytotoxin at 4 and 10°C in either whole or skim milk, at the same rate as in the semisynthetic growth medium.