Intra-individual variations of salivary microbial levels in young adults

The variations of salivary levels of total viable flora, oral streptococci, Streptococcus mutans, Lactobacillus and Candida in twenty-three subjects, over a 6-month period, trying to control many potential sources of variability, were investigated. Most subjects showed log count variations of the microbial parameters larger than 1. They were 95.6% (total flora), 91.2% (oral streptococci), 73.9% (lactobacilli), 60.8% (Strep. mutans) and 30.3% (Candida). The intra-individual fluctuations were larger than the fluctuations of the means of the counts between samples. This suggests that the shifts in levels of these micro-organisms were more frequent intra-individually than at a population level. Strep. mutans levels significantly explained Streptococcus-Oral (inverse correlation), Lactobacillus and Candida variability. The reported variations were due to technical and biological factors and suggest that, in order to assess the salivary level of some microbial parameters in an individual, the mean count and the range of counts, obtained by more than two samples taken under the same conditions, should be considered.