Bactericidal action of an average dose of erythromycin in the bronchi.

A study was carried out to establish whether erythromycin stearate was bacteriostatic or bactericidal at the concentrations reached in the bronchial secretion. Twenty-two patients suffering from an acute attack of chronic bronchitis, sustained by streptococci, diplococci, staphylococci or H. influenzae sensitive to erythromycin, were treated with 1500 mg erythromycin per day until symptoms regressed, usually within 3 to 5 days. The results showed that after treatment there was a dramatic reduction in the number of bacterial colonies cultured from the bronchial secretion and marked changes in bacterial morphology were seen using electron microscopy. Further evidence of bactericidal activity was provided by the rapid clinical response of the patients.