THE FREQUENCIES OF ORAL LACTOBACILLI IN THE HUNT-HOPPERT CARIES-RESISTANT AND CARIES-SUSCEPTIBLE RATS IN RELATION TO THE DEVELOPMENT OF CARIES

¹ Departments of Zoology and Chemistry, Michigan State University, East Lansing, Mich.

Oral lactobacilli were recovered more frequently and in greater numbers from caries-susceptible than from caries-resistant rats. Lactobacilli were recovered consistently from nearly all of the susceptible rats that were examined. The percentage of resistant animals from which lactobacilli were recovered was high when the rats were very young, but after the animals were 50 days old, lactobacilli were recovered from approximately 20 per cent of the examinations.

Lactobacilli were recovered from resistant rats which subsequently developed caries in only 36 per cent of the examinations as compared to 99 per cent in susceptible animals. This is an indication that lactobacilli may not be important etiologic agents of dental caries in resistant rats, whereas they may be the most important etiologic agent in susceptibles.