Objective: To study the influence of environmental factors on the two-species biofilm formed by the combinations of Streptococcus oligofermentans (So) with Streptococcus mutans (Sm) and Streptococcus sanguinis (Ss) with Sm so as to evaluate the role of So in maintaining the microecological balance of the oral cavity. Methods: Single-and two-species biofilms were grown on saliva-coated surfaces (glass tube and 96-well plate). Colony-counting method and safranin staining method were used to measure the biofilms formed under various oxygen conditions (aerobic and anaerobic), sucrose conditions (0%, 1% and 5% sucrose concentrations) and pH conditions (5.5, 6.0, 6.5, 7.0, 7.5 and 8.0). Results: Comparing the numbers of Sm in two co-cultures under various conditions, Sm counts in So+Sm group [(7.70±2.46)×10(8) CFU/ml] were significantly lower than those in Ss+Sm group [(9.00±1.13)×10(8) CFU/ml] in aerobic environment (P<0.05). Sm counts in So+Sm group [(2.80±0.52)×10(8) CFU/ml] were also significantly lower than those in the Ss+Sm group [(4.00±1.25)×10(8) CFU/ml] in anaerobic environment (P<0.05). The Sm counts in So+Sm group [(8.90±0.82)×10(8) CFU/ml] were significantly higher than those in Ss+Sm group [(7.50±1.73)×10(8) CFU/ml] in 0% sucrose environment (P<0.05). The Sm counts in So+Sm group [(5.70±2.94)×10(8) CFU/ml] were significantly lower than those in Ss+Sm group [(10.30±3.21) ×10(8) CFU/ml] in 1% sucrose environment (P<0.05). The Sm counts in So+Sm group [(6.10±1.71)×10(8) CFU/ml] were also significantly lower than those in Ss+Sm group [(7.40±1.20)×10(8) CFU/ml] in 5% sucrose environment (P<0.05). The Sm counts in So+Sm group [(3.50±1.50)×10(8) CFU/ml] were significantly lower than those in Ss+Sm group [(10.70±2.80)×10(8) CFU/ml] in pH7.0 environment (P<0.05). Comparing the formation of biofilm after 24 h cultivation, the Sm counts in So+Sm group were significantly lower than those in Ss+Sm group both in aerobic and anaerobic environments (P<0.05). The Sm counts in So+Sm group were significantly higher than those in Ss+Sm group in 0% sucrose environment (P<0.05). The Sm counts in So+Sm group were significantly lower than those in Ss+Sm group in 1% and 5% sucrose and pH 7.0 environments (P<0.05). Both So and Ss had no inhibitory effect on Sm in pH5.5 and pH8.0 environments. Conclusions: In the in vitro two-species co-culture systems, So showed stronger inhibitory effects than Ss on Sm and its inhibitory ability might influenced by various environmental factors.
目的： 比较不同环境条件对寡发酵链球菌（简称寡链）与变形链球菌（简称变链），血链球菌（简称血链）与变链双菌种生物膜形成的影响，评估寡链在维持口腔微生态平衡中的作用。 方法： 分别在唾液包被的光滑玻璃表面和唾液包被的聚丙乙烯表面构建体外单菌种及双菌种生物膜模型，运用菌落计数法和番红精染色法测定不同氧环境（有氧和无氧）、不同蔗糖环境（无蔗糖、1%蔗糖环境和5%蔗糖环境）和不同pH环境（pH值为5.5、6.0、6.5、7.0、7.5及8.0）下寡链与变链、血链与变链双菌种生物膜的形成情况。 结果： 双菌种共培养中变链菌落数：有氧环境下，寡链+变链组菌落数[（7.70±2.46）×10(8) CFU/ml]显著低于血链+变链组[（9.00±1.13）×10(8) CFU/ml]（P<0.05）。无氧环境下，寡链+变链组菌落数[（2.80±0.52）×10(8) CFU/ml]亦显著低于血链+变链组[（4.00±1.25）×10(8) CFU/ml]（P<0.05）。在无糖环境下，寡链+变链组菌落数[（8.90±0.82）×10(8) CFU/ml]显著高于血链+变链组[（7.50±1.73×10(8)）CFU/ml]（P<0.05）；1%蔗糖环境下，寡链+变链组菌落数[（5.70±2.94）×10(8) CFU/ml]显著低于血链+变链组[（10.30±3.21）×10(8) CFU/ml]（P<0.05）；5%蔗糖环境下，寡链+变链组菌落数[（6.10±1.71）×10(8) CFU/ml]亦显著低于血链+变链组[（7.40±1.20）×10(8) CFU/ml]（P<0.05）。pH7.0环境下，寡链+变链组菌落数[（3.50±1.50）×10(8) CFU/ml]显著低于血链+变链组[（10.70±2.80）×10(8) CFU/ml]（P<0.05）。双菌种共培养24 h生物膜总量：两种氧环境下寡链+变链组均显著低于血链+变链组（P<0.05）。无糖环境下寡链+变链组显著高于血链+变链组（P<0.05），蔗糖环境（1%和5%）和pH 7.0环境下寡链+变链组均显著低于血链+变链组（P<0.05）。在pH 5.5和8.0环境下，寡链和血链均失去对变链的抑制能力。 结论： 在体外双菌种共培养环境下，寡链具有较血链更强的抑制变链的能力，且其抑制能力受环境条件的影响。.
Keywords: Oxygen; Streptococcus mutans; Streptococcus oligofermentans; Streptococcus sanguinis; Sucrose; pH values.