Mutans streptococci에 대한 polyphosphate의 항균효과

ANTIBACTERIAL EFFECT OF POLYPHOSPHATES ON MUTANS STREPTOCOCCI

치아우식증의 원인균인 S. mutans GS5와 S. sobrinus 6715에 대한 polyP의 효과를 관찰하여 보다 안전하고 효과적인 치아우식증 예방을 위한 임상적용의 가능성을 고찰하고자 첫째, 다양한 사슬길이의 polyP를 첨가한 후 흡광도를 측정하여 MIC를 결정하고, 둘째, 실험균주를 흡광도 $0.3{\sim}0.5$까지 증식시킨 후 MIC 농도의 polyP를 첨가하여 흡광도의 변화를 측정함으로써 균주증식 후 성장 억제효과를 관찰하였으며, 셋째, 생균수 측정으로 polyP의 항균효과를 평가하였고, 넷째, 핵산유리의 정도로 polyP의 킬레이션 작용여부를 관찰하였으며, 다섯째, polyP의 비수용성 글루칸 합성능력을 관찰하였으며, 여섯째, 투과전자현미경으로 세포막과 세포질 내의 구조적 변화를 관찰하였다. 이상의 연구를 통하여, polyP의 살균작용이 S. mutans와 S. sobrinus에 대한 성장을 억제시키는 효과가 있는 것으로 가늠된다. 이와 같은 성장 억제효과는 polyP의 킬레이션에 의한 것이라기보다는 균주 세포의 구조적, 형태적 변화가 주된 요인이었던 것으로 판단된다.

Mutans streptococci, especially S. mutans and S. sobrinus strongly implicated in pathogenesis of dental caries, the major cause of tooth loss in children. Use of an antibacterial agent controlling dental caries has been rationalized. The present study was performed to observe the antibacterial effect of inorganic polyphosphates (polyP) on S. mutans and S. sobrinus. S. mutans GS5 and S. sobrinus 6715 were grown in brain-heart infusion broth with or without polyP. Minimal inhibitory concentration (MIC) of polyP for S. mutans GS5 was determined to be 0.08% and that for S. sobrius 6715 was 0.17%. PolyP 15 added to the growing culture of S. mutans GS5 and S. sobrinus 6715 at their exponential phase was as effective in inhibiting the growth of S. mutans GS5 and S. sobrinus 6715 as polyP added at the very beginning of the culture. More than 85% of the cells lost their viability determined by viable cell count when polyP 15 was added to the culture of growing S. mutans GS5 at MIC, suggesting that polyP 15 has bacterial effect on the bacterium. And more than 99.9% of the cells lost their viability determined by viable cell count when polyP 15 was added to the culture of growing S. sobrinus 6715 at MIC, suggesting that polyP 15 has bacterial effect on the bacterium. Intracellular nucleotide release from S. mutans CS5 and S. sobrinus 6715 was increased in the presence of polyP 15 for 5h but was not really reversed by the addition of divalent cations like $Ca^{++}\;and\;Mg^{++}$. The majority of the cells appeared to be atypical in their shape, demonstrating accumulation of highly electron-dense granules and ghost cells. The overall results suggest that polyP have a strong bactericidal activity against S. mutans and S. sobrinus in which lysis in relation to chelation may not play the major role but unknown mechanism that possibly affects the viability of the bacterium may be involved. PolyP may be used as an agent for prevention of dental caries.