RELATION OF CHOLESTEROL-STIMULATED STAPHYLOCOCCUS-AUREUS GROWTH TO CHRONIC BLEPHARITIS

Purpose. Many types of chronic blepharitis have been believed to be pr imarily microbial in origin; however, it was proposed that differences and changes in lipid composition of meibomian secretion may be the in itiating factor in some of these. It was recently reported that there are two subgroups of normals, those whose meibomian secretions contain high levels of cholesterol esters and those whose secretions contain very low levels of these esters. Thus, these subgroups of normals were defined on the basis of detailed lipid analyses of meibomian secretio ns from individuals showing no clinical signs of chronic blepharitis. All secretions from patients in the various disease groups contain hig h levels of these esters. Based on previous observations that in some chronic blepharitis disease groups certain Staphylococcus species were capable of hydrolyzing cholesterol esters, the authors tested the hyp othesis that the resulting cholesterol might affect growth of Staphylo coccus aureus. Methods. Staphylococcus aureus growth stimulation in Mu eller-Hinton broth by cholesterol was determined by colony forming uni ts. Growth stimulation by cholesterol and other additives was also det ermined by the optical density 650 nm method. Statistical analyses inc luded analysis of variance and the Student's t test. Results. Choleste rol stimulated Staphylococcus aureus growth was significant during the first 24 hr period (20% increase at 25 muM cholesterol, P < 0.02), an d for the total 48 hr period (40% increase at 400 muM cholesterol, P < 0.005) when compared to the respective control. Growth stimulation, d etermined by OD at 650 nm, in the presence of cholesterol was signific antly greater (P < 0.02) than that in the presence of either sitostero l or cholestanol when the sterol concentration was 190 muM. Conclusion . These results suggest that the presence and hydrolysis of cholestero l esters of meibomian secretions may contribute to the proliferation o f Staphylococcus spp, especially Staphylococcus aureus, observed in so me chronic blepharitis disease groups.