Abstract: In this study, a rapid and quantitative method for the detection of viable bacterial counts of Streptococcus thermophilus and Lactobacillus bulgaricus in fermented milk was established using propidium monoazide (PMA) combined with quantitative loop-mediated isothermal amplification (PMA-qLAMP). The PMA treatment conditions for S. thermophilus and L. bulgaricus were optimized. A linear relationship was fitted between the logarithm of bacterial concentration and cycle threshold (Ct) value. The limit of quantification for S. thermophilus and L. bulgaricus was 7.2 × 103 and 5.6 × 104 CFU/g, respectively. The PMA-qLAMP method was applied to measure viable bacterial counts in commercial fermented milk, demonstrating good sensitivity and practicality.

Key words: fermented milk; loop-mediated isothermal amplification; propidium monoazide; lactic acid bacteria

摘要： 基于实时荧光定量环介导等温扩增（quantitative loop-mediated isothermal amplification，qLAMP）技术建立发酵乳中嗜热链球菌和保加利亚乳杆菌活菌数快速定量方法。通过优化嗜热链球菌和保加利亚乳杆菌叠氮溴化丙锭（propidium monoazide，PMA）处理条件，对菌浓度对数与相应的循环阈值进行线性拟合，构建标准曲线，建立PMA-qLAMP检测方法。结果表明，该方法对嗜热链球菌的最低定量限为7.2×103 CFU/g，对保加利亚乳杆菌的最低定量限为5.6×104 CFU/g，将该方法应用于市售发酵乳产品活菌数定量检测，显示出良好的灵敏度和实用性。

关键词: 发酵乳；环介导等温扩增；叠氮溴化丙锭；乳酸菌