Characterization and biological activity of the monocytosis-producing agent of Listeria monocytogenes.

Experiments directed toward determining the lipids in extracts of Listeria monocytogenes containing monocytosis-producing agent (MPA) and the effect of these extracts on several biochemical parameters previously shown to change during experimental Listeria infection were conducted. MPA-containing extracts were found to be a complex of lipids with glycerides, glycolipids, and phospholipid being present. No common cell wall carbohydrates were found. A glyceride, designated glyceride A, was determined to cause the characteristic mononuclear response observed in mice injected with MPA-containing extracts. Fasted MPA-treated animals showed less gluconeogenesis than did controls. Blood glucose levels declined in MPA-treated animals. Increases observed in both blood urea nitrogen and plasma glutamic-pyruvic transaminase were greater in the control groups. Incorporation of (14)C-alanine into liver glycogen was depressed in MPA-treated animals. Liver steroid levels in the control groups increased during fasting and remained elevated for the duration of the experiments, while levels in the MPA-treated groups declined initially and showed no increase until 72 hr after injection. MPA appears to affect steroid metabolism and consequently the animals' homeostatic mechanisms seem to be impaired. Possibly as a consequence, carbohydrate metabolism is altered. The apparent effect of MPA on steroid metabolism and on the gluconeogenic process may indicate participation in the carbohydrate derangement observed in experimental Listeria infection.