对氨基苯甲酸对变形链球菌生长影响的体外实验

目的:探讨不同浓度的对氨基苯甲酸(PABA)对变链菌生长的影响。方法:将变形链球菌ATCC25175(血清c 型)在改良Carlsson培养基中厌氧培养,实验组在其中加入不同浓度(10-10~10-3gPL)的PABA液厌氧培养48 h后采用紫外可见分光光度仪测定细菌浓度OD值(K=550 nm),并在琼脂平板上培养观察细菌生长情况,进行菌落计数。结果:菌液比浊及菌落计数结果均表明PABA确有促进变链菌生长的能力,当PABA的浓度从10-10~10-4gPL增大时,其促进变链菌生长的能力增强,但当PABA浓度增大到10-3gPL,则促进变链菌生长的能力开始下降。当PABA 浓度为10-9~10-3gPL时,实验组的细菌生长明显高于对照组(P<0105)。结论:当PABA的浓度为10-4gPL时,其促进变链菌生长的能力达最强,高于或低于此浓度,这种促生长作用均下降。     

对氨基苯甲酸对变形链球菌表面疏水性的影响

目的　研究血链球菌合成的生态调节因子---对氨基苯甲酸(PABA)对变形链球菌细胞表面疏水性的影响,从而进一步了解PABA影响细菌粘附的机制。方法　在不同PABA浓度(10-9g/L、10-7g/L、10-4g/L)的改良Carls- son液体培养基中厌氧培养变形链球菌,并采用微生物粘着碳氢化合物法测试细胞表面疏水性。结果　低浓度的 PABA可增强变形链球菌细胞表面疏水性,当浓度增加到一定范围则可降低其细胞表面疏水性。结论　PABA可能通过降低细菌非特异性疏水作用而抑制变形链球菌的粘附。     

血液链球菌产生对氨基苯甲酸的实验研究：Ⅱ.对氨基苯甲酸的定 …

运用已建立的反相高效液相色谱分析法，对血链菌Ｓ３４产生的ＰＡＢＡ进行定性定量研究。结果显示；１．血链菌Ｓ３４确能产生ＰＡＢＡ，其平均量为１．２３６μｇ／ｍｌ；２．ＰＡＢＡ的平均回收率为８０％左右，线性相关性好，本文结果为进一步研究血链菌产生ＰＡＢＡ的影响因素以及ＰＡＢＡ在牙菌斑微生态中的作用奠定了实验基础。     

壳寡聚糖抑制变形链球菌的致龋能力

目的研究壳寡聚糖(chitooligosaccharide,COS)对变形链球菌生长、产酸及粘附能力的影响。方法选用变形链球菌标准株ATCC 25175,采用对倍稀释法测定COS对变形链球菌的最低抑菌浓度(minimum inhibitory concentration,MIC)和最低杀菌浓度(minimum bactericidal concentration,MBC);采用菌落计数法,通过时间—杀菌曲线的变化,分析COS对细菌生长速度的影响;将COS及变形链球菌菌悬液各1 m L接种于无菌试管内厌氧培养,使COS的终浓度分别达到1/2 MIC、1/4 MIC、1/8MIC,测定上清液p H变化并绘制p H曲线;采用液体闪烁计数法测定壳寡聚糖对变形链球菌粘附羟磷灰石能力的影响。结果 COS对变形链球菌的MIC和MBC分别为2.00 g/L和4.00 g/L;COS能有效抑制变形链球菌的生长,较高浓度时对细菌还具有杀菌作用。亚抑菌浓度的COS可显著影响变形链球菌的产酸性和粘附能力,并且这种抑制作用呈浓度依赖性。结论 COS对变形链球菌的生长、产酸和粘附能力均有抑制作用。     

Lysozyme enhances the inhibitory effects of the peroxidase system on glucose metabolism of Streptococcus mutans.

The combined effect of the salivary peroxidase system and lysozyme on the glucose uptake of Streptococcus mutans NCTC 10449 was investigated. The bacteria were grown to late-exponential phase, washed, re-suspended in buffer at pH6, and incubated with (1) 50 micrograms/mL lysozyme from human milk for 60 min; (2) 7-15 mumol/L hypothiocyanous acid/hypothiocyanite for 10 min; and (3) lysozyme for 60 min prior to addition of and incubation with hypothiocyanous acid/hypothiocyanite for 10 min. Glucose uptake was initiated by adding the bacterial suspensions to 10 mL of pre-warmed 50 mumol/L glucose containing 0.98 mumol/L D-(U-14C-)-glucose, and the mixture was incubated in a shaking water-bath at 37 degrees C. Samples were withdrawn at various time intervals, rapidly filtered through 0.45-microns membranes, washed with ice-chilled buffer, and the incorporated radioactivity determined. Lysozyme stimulated S. mutans glucose uptake slightly, but significantly inhibited S. rattus glucose metabolism. A 20-30% inhibition of radiolabeled glucose incorporation was observed with hypothiocyanous acid/hypothiocyanite alone. Incubation of the bacteria with lysozyme prior to addition of hypothiocyanous acid/hypothiocyanite containing peroxidase resulted in a total inhibition of the glucose uptake. In contrast, lysozyme in combination with hypothiocyanous acid/hypothiocyanite without peroxidase gave only a 30-50% inhibition. The addition of 5 mmol/L dithiothreitol after incubation with lysozyme and hypothiocyanous acid/hypothiocyanite eliminated the inhibition of the bacterial glucose uptake. The viability of S. mutans was not affected by treatment with any of the components used. Our results indicate that physiological concentrations of lysozyme and the salivary peroxidase system components have a synergistic effect which results in a significant inhibition of glucose metabolism by S. mutans.     

The effect of cocoa polyphenols on the growth, metabolism, and biofilm formation by Streptococcus mutans and Streptococcus sanguinis

The aim of this study was to determine if cocoa polyphenols could interfere with biofilm formation by Streptococcus mutans or Streptococcus sanguinis, and reduce acid production from sucrose by S. mutans. The antimicrobial activity of cocoa polyphenols was assessed against cariogenic (S. mutans) and health-associated (S. sanguinis) species by minimum inhibitory concentration assays. Cocoa polyphenol dimer, tetramer, and pentamer inhibited the growth of S. sanguinis, whereas the growth of S. mutans was unaffected. However, pretreatment of surfaces with cocoa polyphenol pentamer (35 microM) reduced biofilm formation by S. mutans at 4 and 24 h, whereas the effects on S. sanguinis were less consistent. In contrast, brief exposure of preformed biofilms to pentamer either had no significant effect or resulted in increased counts of S. mutans under certain conditions. Cocoa polyphenol pentamer (500 microM) significantly reduced the terminal pH, and inhibited the rate of acid production by S. mutans at pH 7.0. In conclusion, cocoa polyphenols can reduce biofilm formation by S. mutans and S. sanguinis, and inhibit acid production by S. mutans.     

菌斑固相、变形链球菌及葡聚糖对酸的缓冲作用

目的研究糖代谢后菌斑固相缓冲力的变化及影响因素。方法采集40名18~21岁的大学生的饥饿牙菌斑,体外10%蔗糖孵育1h。体外制备无糖培养和2%蔗糖培养的变链菌团。以25mmol/L KCl制备菌斑固相、变链菌团和不溶性葡聚糖混悬液及可溶性葡聚糖溶液,用1mmol/LHCl滴定并计数细菌密度,统计学分析。结果变链菌团代谢蔗糖后的缓冲容量为(0·099±0·047)mmol/L,比无蔗糖培养的变链菌团的缓冲容量(0·609±0·202)mmol/L低,且缓冲力随细菌密度降低直线下降,葡聚糖几乎没有缓冲作用[(0·028~0·032)mmol/L]。人牙菌斑固相缓冲力的变化规律与体外纯菌培养研究结果一致。结论菌斑固相缓冲力与所含细菌密度密切相关。     

茶色素抑制变形链球菌的实验研究

目的研究茶色素对变形链球菌的抑制作用及其机制。方法以茶多酚为对照,采用液体稀释法体外抑菌实验比较不同纯度茶色素对变链菌族的变形链球菌和远缘链球菌生长、产酸和形态学的影响。结果纯度为20%、40%、60%的茶色素均能抑制变链菌生长,其中纯度为40%的茶色素抑菌效果最佳,与纯度90%的茶多酚相当,两者均能明显抑制变链菌产酸(P<0.05),透射电镜观察发现茶色素主要引起变链菌胞质空泡性变,茶多酚则破坏细菌细胞壁,两者抑菌机理不同。结论不同纯度茶色素中,纯度为40%的茶色素抑制变链菌效果最佳,抑菌过程中茶色素各个组分存在着协同作用。     

变形链球菌耐氟菌株的诱导及产酸性的实验研究

目的　探讨变形链球菌耐氟菌株致龋毒力的变化。方法　在含有不同氟浓度的TSA上逐步诱导变形链球菌 (S mutansIngbritt)产生耐氟菌株Ingbritt FR ,用气相色谱法检测耐氟菌株的产酸量及降低pH值的能力 ,并与亲代野生菌株进行比较。结果　Ingbritt FR在体外诱导成功并稳定传代培养 ;当氟化物存在时 ,耐氟菌株的产酸量大于亲代野生株 ;无氟化物存在时 ,初始pH≥ 5 5时其产酸量小于亲代株 ,pH <5 5时则大于亲代株 ,差异有显著性。结论　变形链球菌耐氟菌株具有致龋性 ;在菌斑正常氟浓度情况下 ,其致龋力可能大于亲代野生株。     

有机弱酸对变链菌产酸作用的影响

目的 探讨有机弱酸苯甲酸、苹果酸、柠檬酸对口腔主要致龋菌变形链球菌的作用，并与氟化钠进行比较；探讨上述弱酸作为防龋剂的可能性。方法 将变形链球菌Smutans Ingbritt置入含有不同浓度的氟化钠、苹果酸、柠檬酸、苯甲酸的液体培养基TSB中生长48h，测定菌液的终末pH值，推测上述弱酸对细菌产酸能力的抑制作用，结果 苯甲酸、苹果酸、柠檬酸的抑菌所需浓度较氟化钠浓度高，且具浓度依赖性。结论 氟化钠抑制变形链球菌产酸作用最好；而有机弱酸苯甲酸、苹果酸、柠檬酸在较高浓度下，才有不同程度抑制变形链球菌产酸作用，但该浓度却有可能对牙釉质产生脱矿作用。