The role of glycocalyx in surface phagocytosis of Bacteroides spp., in the presence and absence of clindamycin.

The influence of isolated glycocalyx from Bacteroides thetaiotaomicron and B. fragilis on surface phagocytosis of clindamycin-treated and -untreated homologous and heterologous species was studied. When homologous or heterologous isolated glycocalyx was added to clindamycin-treated B. thetaiotaomicron or B. fragilis before incubation with PMNL, phagocytosis was reduced to levels observed in the untreated control bacteria, but addition of glycocalyx to untreated control strains showed no reduction of phagocytosis. When isolated bacteroides-glycocalyx was added to Staphylococcus aureus or S. epidermidis, phagocytosis of both clindamycin-treated and -untreated bacteria was significantly reduced. The isolated glycocalyx preparations were analysed by thin layer and gas-liquid chromatography; these preparations were free of lipopolysaccharides. The isolated glycocalyx did not affect PMNL viability. Our findings suggest that the glycocalyx is an important virulence factor because it impairs phagocytosis of Bacteroides spp. by PMNL. Clindamycin may enhance opsonophagocytosis of bacteroides by altering the glycocalyx.