A Mortality Enhancing Extract Isolated from Listeria Monocytogenes

Abstract

The injection of a crude extract (MEF) prepared from cells of Listeria monocytogenes reduced the resistance of mice, guinea pigs, rabbits and rhesus monkeys to infection with Listeria. The resistance of mice to a number of other species of bacteria, both Gram-positive and Gram-negative, was also impaired by the cell material. The extract was heat stable when held at temperatures up to 70°C for 30 min. It was effective when administered prior or subsequent to infection or when injected by a route other than that used for challenge. Injection of MEF into guinea pigs caused (a) a loss of weight, (b) changes in body temperature, (c) qualitative and quantitative alteration of the white blood cells, including monocytosis and (d) changes in serum lysozyme, properdin and complement.