Biological activity of Pityrosporum. I. Enhancement of resistance in mice stimulated by Pityrosporum against Salmonella typhimurium.

The effect of administration with Pityrosporum (P. orbiculare, P. ovale, P. pachydermatis and Pityrosporum sp.) on susceptibility of mice to Salmonella typhimurium infection was studied. Pretreatment of mice with 50 mg (wet weight) of killed Pityrosporum 4 days prior to the intraperitoneal (i.p.) challenge of 4 X 10(5) (10 LD50) S. typhimurium elicited resistance comparable to that induced by 500 micrograms (dry weight) of killed Propionibacterium acnes and over 30% of the infected mice survived. Among the species tested, P. pachydermatis was slightly less effective. The challenged organisms were not detected from the blood of mice treated with Pityrosporum but were present in the liver and spleen in approximately level amounts (10(4)-10(5)/organ) during the course of testing. These results suggest that the increased resistance in mice is the result of stimulation of the reticuloendothelial system by Pityrosporum.