In vivo bactericidal effect of 0.2% chlorhexidine but not 0.12% on salivary obligate anaerobes

ObjectivesTo evaluate the in vivo antimicrobial activity on the salivary flora of a single mouthrinse of chlorhexidine (CHX) digluconate, analysing the influence of its concentration (0.2% versus 0.12%).MethodsThe study group was formed of 20 adult volunteers with a good oral health status. Non-stimulated saliva samples were collected under basal conditions and at 30 s and 1 h after a single mouthrinse with sterile water, 0.2% or 0.12% CHX digluconate. Serial dilutions were then performed and the resulting samples were cultured on conventional culture media for aerobes/facultative anaerobes and obligate anaerobes. The number of colony forming units (CFU/ml) was then determined and the results expressed on a decimal log scale (log10 CFU/ml).ResultsA significant reduction in the total bacterial population was observed at 30 s and 1 h after the mouthrinse with both CHX concentrations; this antimicrobial activity was more pronounced on the obligate anaerobes. The antimicrobial activity of 0.2% CHX on the salivary flora at 30 s and 1 h after the mouthrinse was significantly greater than that of 0.12% CHX. Only 0.2% CHX showed bactericidal activity (differential factor ≥ 3 log10 CFU/ml) against salivary obligate anaerobes.ConclusionThe greater antimicrobial activity of 0.2% CHX confirms the influence of the concentration on its antibacterial activity. In consequence, the CHX concentration seems to be an important factor to guarantee a high antibacterial activity in those clinical situations where it is required.