Effect of clindamycin and lincomycin therapy on faecal flora.

Bacterial counts were carried out on the faeces of 160 patients receiving clindamycin or lincomycin treatment for bacterial infections. In all the patients the total bacteroides count was significantly reduced while strains of Enterobacteriaciae, yeasts, and streptococci were correspondingly increased. Severe diarrhoea developed in 25 (16%) patients, but this could not be related to a change in faecal flora. Diarrhoea was most common when clindamycin was given prophylactically, women were more affected than men, and the incidence was highest in those aged over 60 years. No cases of pseudomembranous colitis were seen. Although clindamycin is a valuable antibiotic for treating established severe anaerobic bacterial infections it should be used cautiously in elderly patients.