Effect of Bacterial Endotoxin on Experimental Fungal Infections

Summary Escherichia coli endotoxin was administered to mice prior to challenge with 5 × 10 6 Candida albicans , 5 × 10 6 Rhizopus arrhizus or 1 × 10 6 Blastomyces dermatitidis organisms. When 100 or 400 µg endotoxin was given 1 hr prior to challenge with C. albicans , significant acceleration in mortality occurred, while the same doses of endotoxin given 24 hr before challenge delayed lethality. Similar protection but no enhancement of lethality was noted for R. arrhizus , while reproducible alterations in lethality were not demonstrable with B. dermatitidis . Protection against C. albicans appeared to have a bimodal character, being maximal at 24 hr and 6 days following endotoxin administration. Sterile sera were passively administered in amounts of 1.0 ml to normal mice, which were then challenged 1 hr later with C. albicans . Lethality was significantly delayed only in the animals receiving sera collected 24 hr after endotoxin but not in the groups receiving saline, normal sera or sera obtained 6 days following endotoxin. These studies demonstrate that serum factors are important in the initial phase of increased resistance against C. albicans induced by endotoxin.