Phagocytic and serum killing of capsulate and non-capsulate Bacteroides fragilis

Abstract
SUMMARY. The relative susceptibilities of capsulate and non-capsulate variants of Bacteroides fragilis to serum and phagocytic killing were investigated. The capsule of B. fragilis did not confer resistance to serum killing. Phagocytic killing of non-capsulate B. fragilis occurred at bacterial concentrations of 1 x 106 and 1 x 107 cfu/ml. Capsulate B. fragilis organisms were also phagocytosed and killed at a concentration of 1 x 106 cfu/ml, but phagocytosis and killing were impaired at a concentration of 1 x 107 cfu/ml.