COMPARATIVE STUDIES ON LACTOBACILLI ISOLATED FROM THE MOUTH AND INTESTINE

¹ Walter G. Zoller Memorial Dental Clinics and the Department of Bacteriology and Parasitology, University of Chicago, Chicago, Ill.

Lactobacilli were isolated from saliva and stool specimens from a series of patients hospitalized in a children's hospital for various illnesses unrelated to dental conditions. Cultures were made at intervals over a period of about 6 weeks. At each examination period representatives of each recognizably different type of colony were chosen for subculture and further study. Independent clinical examination of the teeth was made before, during or after the period during which specimens were collected for culturing.

No lactobacilli were found in the stool recimens from 5 children whose teeth were caries free. Lactobacilli were recovered only occasionally and then in small numbers from saliva samples obtained during the same study periods from these 5 children.

Lactobacilli were found in 66% of the fecal specimens and 93% of the saliva samples from 11 individuals who had definite dental caries activity. There was a rough correlation between the number of lactobacilli in the saliva and the frequency of successful isolation of these organisms from the stools.

Approximately 100 cultures obtained from saliva and stool samples provided by 11 of the patients were maintained in laboratory culture media over a period of 16 to 22 months during which time repeated observations were made on gross and microscopic morphology, fermentation capacity and immunological reaction. None of the strains in either the oral or intestinal group exhibited characteristics not found among strains in the other group. Although there were some differences in the proportions of various colony types and fermentation groups at the time of isolation these differences disappeared after a period of laboratory cultivation. More than half of the cultures were tested immunologically in type specific antisera and the same types were found in about the same proportions in the two groups.

Paired, oral and intestinal cultures from 8 individuals, studied comparatively, were found to be identical in morphology, fermentative action and immunological reaction.

It is concluded that the cultures isolated from the intestine had their origin in the mouth and that the supply of these organisms is continually replenished by the swallowing of lactobacillus-contaminated saliva. The relationship of the oral lactobacillus with the intestinal Lactobacillus acidophilus is discussed.