Extracellular and bacterial factors influencing staphylococcal phagocytosis and killing by human polymorphonuclear leukocytes

Abstract

Extracellular and bacterial factors that influence the phagocytosis and killing of staphylococci by human polymorphonuclear leukocytes were studied. Staphylococcus epidermidis strains were, in general, more rapidly phagocytized than were S. aureus strains. However, 2 strains of S. epidermidis had a very slow rate of ingestion. Although the rate of phagocytosis of S. aureus Wood 46 was greater than that of S. aureus 502A, the Wood 46 strain was more difficult to kill. Serum was essential for phagocytosis of both S. aureus and S. epidermidis. The opsonic titer of pool serum was similar for S. aureus and S. epidermidis. In normal pooled serum, heat labile factors were more important for effective phagocytosis than they were in immune serum. Although a saturation point for ingestion was reached, the percentage of ingested bacteria that remained alive within the leukocyte remained relatively fixed. Heat killed and live staphylococci were ingested in a similar fashion. The rate of phagocytosis was greatly reduced at 41°C.