Increased susceptibility to pulmonary infection in alloxan diabetic mice

Pulmonary infections in diabetics have received little attention clinically or experimentally despite an impression that diabetics are more prone to pulmonary infections and do poorly with these and all infections. In a mouse model, aerosolized pneumococci were used in order to mimic the natural portal of entry of pneumococci, to investigate susceptibility to pneumococcal infection in alloxan diabetic and normal mice, and to test the hypothesis that insulin therapy would have a protective effect. When exposed to an aerosol created from 10⁸ type III Streptococcus pneumoniae (PnIII)/ml, nondiabetic mice had a higher survival rate than uncontrolled diabetic mice (P < 0.001) and insulin-treated diabetic mice (P < 0.001). Insulin-treated diabetic mice had a significantly decreased death rate compared to untreated diabetic mice (P < 0.05). The data show that alloxan diabetic mice are more likely to succumb to infection from aerosolized pneumococci than are normal mice. Insulin therapy appeared to decrease this susceptibility. A possible clinical inference is that insulin therapy is beneficial in diabetic patients with pulmonary infections.