CELL WALL-DEFICIENT FORMS (L-FORMS) OF LISTERIA-MONOCYTOGENES IN EXPERIMENTALLY INFECTED-RATS

Experimental infections were induced with different bacterial forms of Listeria monocytogenes: parental (S-forms), protoplastic ii-forms) an d combined inoculum of both forms by i. p. injection of rats. The pare ntal bacterial forms (S-forms) were isolated up to 7 days after challe nge from the peritoneal cavity and the liver, while the L-forms were i solated up to 60 days from the peritoneal cavity. Continuous adhesion of L-forms on the peritoneal macrophage surface was found by scanning- electron microscopy. Erythrocyte and leucocyte count as well as some c linical chemistry parameters were measured during infections. They sho wed different dynamics in the three experimental groups. Histomorpholo gical changes in the liver (microabscesses and mononuclear cellular gr anulomas) of infected animals were observed. They were less intensive and appeared later in rats infected with L-forms. The experiments demo nstrated that infections caused by parental bacterial forms and by com bined inoculum took an acute course, while the infection caused by L-f orms could be distinguished as a prolonged and persistent one.