Protective effect of acidic mannan fraction of bakers' yeast against Staphylococcus aureus infection in mice.

Protective activity of an acidic fraction of bakers' yeast mannan containing protein and phosphorus, designated as WAM025, against infection of Staphylococcus aureus beta H 248 strain in mice was investigated. WAM025 elicited a marked increase in the survival ratio of mice challenged with viable cells of the S. aureus strain, 5 X 10(8) cells per mouse, when the fraction was administered to mice 150 mg/kg/d, 5 times, intraperitoneally. This effect was stronger than that of WNM, a neutral fraction of mannan obtained from the same bakers' yeast. The difference seemed to correlate with the strength of activating effects of WAM025 and WNM on the reticuloendotherial system of the host animal. WAM025 induced higher activities of serum lysozyme and carbon clearance in mice than WNM. Also, mice treated with WAM025 showed a greater increase in number and activity of oxygen-generating blood polymorphonuclear leucocytes than mice treated with WNM.