Ecological effects of triclosan and triclosan monophosphate on defined mixed cultures of oral species grown in continuous culture.

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The effects of triclosan and its phosphorylated derivative, triclosan monophosphate were studied using a continuous culture microcosm model. Two conditions were simulated, a caries-like state (pH 5.5 with artificial saliva plus glucose as growth medium) and a periodontal disease-like state (pH 7.5 with BHI plus yeast extract, haemin and cysteine as growth medium). Both cultures were maintained anaerobically at 37 degrees C at a growth rate of 0.1/h. Steady-state chemostats were pulsed with triclosan or triclosan monophosphate (initial concentrations between 20 and 40 mg/L) and changes in the ecological composition noted after 6 h. The caries-like microcosm steady state was dominated by streptococci, Lactobacillus and Veillonella sp. with low but detectable levels of Neisseria, Actinomyces and Fusobacterium sp. No significant ecological shifts occurred following pulses of either antimicrobial agent; all species were affected to approximately the same degree. The periodontal disease-like microcosm steady state was dominated by streptococci, Fusobacterium, Veillonella, Actinomyces, Prevotella and Porphyromonas sp. with low numbers of Neisseria and Lactobacillus sp. Significant ecological shifts were apparent following pulses of triclosan. The streptococci became the dominant group followed by Fusobacterium sp. For triclosan monophosphate, the streptococci again became dominant although Lactobacillus and Actinomyces were now the main sub-dominant species and Gram-negative anaerobes including Fusobacterium sp. were markedly inhibited. It is concluded that in the periodontal disease state, both triclosan and triclosan monophosphate affected the Gram-negative anaerobes to a greater extent than the Gram-positive groups and that this effect was more marked for triclosan monophosphate.