Saliva-induced aggregation of micro-organisms from skin, tooth surfaces, oral mucosa, and rectum

A total of 57 bacterial strains were isolated from tooth surfaces, oral mucosa, skin of the upper lip, and rectum of 3 persons. Identification of the strains indicated that each type of surface had a characteristic microflora. Aggregation of bacterial suspensions, induced by salivary agglutinins, was measured spectrophotometrically as the decrease in optical density (OD) by time. The aggregation curves for the oral strains followed a sigmoid pattern. The aggregation rates varied between individuals and strains. Most fecal strains showed an aggregation pattern which differed from that of the oral strains and was characterized by only a small, initial decrease in OD. The few strains, mainly Propionibacterium strains, collected from the skin of the upper lip did not aggregate. It appears from the data that several mechanisms are involved in the retention of bacteria to surfaces.