The association between dietary sucrose consumption and microbial population shifts at six oral sites in man.

Sucrose-related microbial population shifts were evaluated at 6 oral sites in 22 volunteers, who consumed high-sucrose diets for 21 days followed by low-sucrose diets for 21 days. Culturing was performed at 0, 12, 21, 33 and 42 days of the 6-week experiment. Over 50,000 microbial isolates were characterized and analysed. Analysis of initial cultures showed the following site-specific microbial characteristics of the 6 sites evaluated: (1) molar fissures harboured higher levels of Neisseria species and showed the highest facultative-to-anaerobic ratio; (2) molar fissures and cervical buccal sites showed high Streptococcus sanguis levels and total Gram-positive cocci and fewer Gram-negative bacilli; (3) the tongue and saliva gave high concentrations of Streptococcus salivarius and Veillonella sp. Sucrose intake was positively related to concentrations of yeasts and Streptococcus mutans in the molar fissures; Actinomyces viscosus in the mandibular approximal site; Strep. mutans, Veillonella sp. and Lactobacillus sp. in the maxillary approximal site and Strep. salivarius on the tongue and in saliva. Sucrose intake was negatively related to concentrations of Neisseria sp. on the tongue and total Gram-positive bacilli in saliva. A definite ecological effect of sucrose on the oral microflora was confirmed. The high inter-subject and site variations of target bacteria and the generally low magnitude of shifts, however, discourage implementation of microbiological criteria in dietary assessments.