Chlorhexidine Effect on Tongue Biofilms using a Perfusion Sobarod Model

OBJECTIVE: The aim of this work was to investigate the microbiological change of the microflora of a tongue biofilm after repeated exposure of Chlorhexidine(CHX). METHODS: The model that was used was a perfusion sobarod biofilm model, which could look at real time responses of certain physiological responses (e.g. volatile sulfur compounds -VSC's) of the biofilm by carbon veil electrode in contact with the sobarod and a Halimeter measuring the effluent gas. To determine the ecological shifts of the perfusate and the biofilm, traditional microbiological techniques (e.g. selective medium) and PCR coupled with microfluidic electrophoresis (Agilent 2100 bioanalyser) were utilized. RESULTS: Experiments where biofilms were treated with chlorhexidine (six treatments of a 1 ml pulse of 0.1% CHX over three days) showed (1) a large reduction in viable count (>90% kill) (2) a [slow] reduction in VSC production rate, consistent with the reduction in microbes rather than direct inhibitory effects on the biotransformation steps (3) a greater killing of the strict anaerobes. Treated biofilms that were allowed to recover over 5 days showed some degree of re-colonization by the survivors but the population numbers were still well below those found in untreated biofilms. The microbiological composition of biofilms treated but allowed to recover was markedly different from the control biofilms, in particular there was less strict anaerobes. The VSC generating capacity of treated and treated- but-recovered biofilms was very much reduced compared to controls. CONCLUSIONS: The bacterial configuration of the tongue biofilm after multi-dose (2x) 0.1% chlorhexidine a day for three days and the re-growth of the biofilm shows a marked difference in counts and variation of microbiological species to the controls.