Increased energy expenditure by granulocytes during phagocytosis of Staphylococcus aureus compared with other staphylococci.

The heat produced by human neutrophils during phagocytosis of different strains of Staphylococcus was analyzed by a flow calorimetric technique. At the same bacteria/leukocyte ratio Staphylococcus aureus yielded heat effects about twice that of other saprophytic staphylococci tested. In parallel experiments the degree of phagocytosis of radiolabeled bacteria was evaluated: S. aureus strains were the least phagocytosed. These data indicate that, for a single phagocytosed bacterium, S. aureus strains yield heat effects three to four times greater than do the saprophytic staphylococci tested (P less than .001). Previous studies have shown that the heat produced by activated neutrophils derives essentially from the aerobic catabolism of glucose involved in the production of bactericidal O2 metabolites and is directly proportional to O2 consumption. The results reported here indicate that less efficient internalization of a staphylococcal strain is correlated with a greater energy expenditure for O2 metabolite formation during the metabolic burst.