EFFECTS OF TRICLOSAN AND TRICLOSAN MONOPHOSPHATE ON MAXIMUM SPECIFIC GROWTH-RATES, BIOMASS AND HYDROLYTIC ENZYME-PRODUCTION OF STREPTOCOCCUS-SANGUIS AND CAPNOCYTOPHAGA-GINGIVALIS IN CONTINUOUS-CULTURE

Dental plaque species, Streptococcus sanguis and Capnocytophaga gingiv alis, were grown in continuous culture with progressively increasing c oncentrations of triclosan or its phosphorylated derivative, triclosan monophosphate (TMP). For both organisms, the maximum specific growth rates decreased with increasing concentrations of triclosan or TMP unt il complete inhibition of growth occurred, which for S. sanguis was at 20 mg/L and 50 mg/L, and for C. gingivalis was at 10 mg/L and 5 mg/L for triclosan and TMP respectively. For both species, biomass levels r emained approximately constant or, in some cases, increased slightly a t low levels of triclosan or TMP. However, biomass levels then decreas ed significantly as the triclosan or TMP concentrations approached let hal levels. For S. sanguis, levels of hydrolytic enzymes (acid phospha tase, leucine aminopeptidase and esterase) generally remained approxim ately constant or increased with increasing concentrations of triclosa n or TMP until close to inhibitory Bevels where enzyme levels were red uced. The ratio of extracellular soluble enzmyes to cell-bound enzymes remained constant or increased slightly with increasing levels of tri closan or TMP. For C. gingivalis, production of hydrolytic enzymes (ne utral phosphatase, leucine aminopeptidase and trypsin-like protease) r emained constant or were reduced when grown with low levels of triclos an and TMP but in some cases increased with higher levels of agents. T he proportion of extracellular soluble activity increased significantl y when concentrations of agent neared inhibitory levels. The results t aken together show that the physiology of cells is significantly alter ed and that hydrolytic enzymes are released from the cells when these are grown in the presence of increasing concentrations of triclosan or TMP. Enzyme release is more pronounced in the Gram-negative C. gingiv alis and indicates that triclosan or TMP can cause membrane perturbati on with subsequent release of membrane-located (S. sanguis) or peripla smic (C. gingivalis) hydrolytic enzymes. S. sanguis was more sensitive to triclosan than TMP while C. gingivalis was more sensitive to TMP. This suggests that, in C. gingivalis, TMP may diffuse into the cell wa il more easily than triclosan and then be converted to triclosan by ph osphatase activity within the cell wall complex, where it may give ris e to high localized concentrations and subsequent cell damage.