Journal of Antimicrobial Chemotherapy, Vol 40, 659-666, Copyright © 1997 by The British Society for Antimicrobial Chemotherapy
J Greenman, C McKenzie and DG Nelson
Dental plaque species, Streptococcus sanguis and Capnocytophaga gingivalis,
were grown in continuous culture with progressively increasing
concentrations 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 until 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 remained approximately
constant or, in some cases, increased slightly at low levels of triclosan
or TMP. However, biomass levels then decreased significantly as the
triclosan or TMP concentrations approached lethal levels. For S. sanguis,
levels of hydrolytic enzymes (acid phosphatase, leucine aminopeptidase and
esterase) generally remained approximately constant or increased with
increasing concentrations of triclosan or TMP until close to inhibitory
levels where enzyme levels were reduced. The ratio of extracellular soluble
enzymes to cell-bound enzymes remained constant or increased slightly with
increasing levels of triclosan or TMP. For C. gingivalis, production of
hydrolytic enzymes (neutral phosphatase, leucine aminopeptidase and
trypsin-like protease) remained constant or were reduced when grown with
low levels of triclosan and TMP but in some cases increased with higher
levels of agents. The proportion of extracellular soluble activity
increased significantly when concentrations of agent neared inhibitory
levels. The results taken together show that the physiology of cells is
significantly altered 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.
gingivalis and indicates that triclosan or TMP can cause membrane
perturbation with subsequent release of membrane-located (S. sanguis) or
periplasmic (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
wall more easily than triclosan and then be converted to triclosan by
phosphatase activity within the cell wall complex, where it may give rise
to high localized concentrations and subsequent cell damage.
ORIGINAL ARTICLES
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
Faculty of Applied Sciences, University of the West England, Frenchat Campus, Bristol, UK.
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