CONFLICTING reports have been published concerning the ability of chlortetracycline and oxytetracycline to reduce the bacterial population of the human intestinal tract. Some investigators consider these drugs useful for this purpose.* In contrast, other workers believe that administration of these antibiotics has only a minor effect on the intestinal flora.f Many of the published studies are concerned with a few fecal cultures on many patients or detailed cultural studies of only a few types of intestinal micro-organisms. The purpose of the present investigation is to make a detailed study of the effect of chlortetracycline and oxytetracycline on the intestinal flora of a few persons in the hope that some of the conflicting opinions may be resolved.
Sixteen normal healthy adult subjects of both sexes were given chlortetracycline orally for a period of five days in a daily dose of 1 gm. (250 mg. four times per day). Three