[Salivary microbial flora of mentally retarded persons with rumination]

The salivary microflora of institutionalized mentally retarded persons with chronic rumination was investigated, especially emphasizing the occurrence of the aciduric microorganisms such as mutans streptococci, lactobacilli and yeasts. 10 of those subjects together with 10 control subjects resident in the same institution were selected at random. The control subjects were mentally retarded but without rumination. Samples of saliva were collected about 2 hours after lunch. The results obtained were as follows: 1. Dental caries was more prevalent and advanced in those ruminating than the control subjects. 2. The mean salivary pH-value in the ruminating subjects was significantly lower than the control subjects. 3. The proportional distribution of the genera or species of salivary microorganisms cultivated on the blood agar plates was similar for both the ruminating and non-ruminating subjects. The only difference was observed in the genus of Actinomyces, which was less frequently isolated from the ruminating subjects. 4. Mutans streptococci, lactobacilli and yeasts recovered from their respective selective media were significantly predominant in those ruminating compared with control subjects. 5. Positive correlations among the cell count of mutans streptococci, lactobacilli and yeasts were found in the ruminating subjects. The yeasts isolated were classified exclusively into Candida albicans. 6. The results described above suggest that long-lasting acidic milieu in the oral cavities of the ruminating subjects favors the proliferation of mutans streptococci, lactobacilli and yeasts, resulting in the prevalence of dental caries in those subjects.