Granulocytes of patients with diabetes mellitus have an impaired capability to engulf bacteria, but it is not clear whether subsequent intracellular killing, which has separate energy sources, is also defective.

We separately assayed engulfment and intracellular killing of Staphylococcus aureus 502a by granulocytes of 17 diabetic patients with fasting hyperglycemia to better characterize the phagocytic defect. Diabetic granulocytes engulfed a smaller proportion than controls of a 106 inoculum of bacteria after 20 minutes of incubation in vitro (56.8 ± 9.4 per cent versus 72.4 ± 3.6 per cent, mean ± S.E. of 10 patients and paired controls, p < 0.05), but after 60 minutes of incubation this defect had disappeared. Intracellular killing of staphylococci by granulocytes from seven diabetics (68.6 ± 8.9 per cent of a 106 inoculum) was less (p < 0.01) than that of paired controls (80.3 ± 4.5 per cent) after two hours of incubation. Seven patients were retested during a period of improved diabetes' control; intracellular killing of staphylococci by granulocytes of six of the seven increased considerably and either exceeded the paired control value or approached it to within 75 per cent.

These data suggest that a primary defect exists in intracellular killing of staphylococci by granulocytes from poorly controlled diabetics in addition to that previously shown in engulfment. This bactericidal activity becomes more efficient when the diabetes is brought under better control.

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