乳酸对三种食源性致病菌的抑菌及杀菌作用

Antibacterial and bactericide activity of lactic acid against three strains of food-borne pathogenic bacteria

选用金黄色葡萄球菌、蜡样芽孢杆菌、埃希氏大肠杆菌3株常见的食源性致病菌,用于测定乳酸的抑菌效果、最小抑菌浓度(MIC)及最小杀菌浓度(MBC),并研究乳酸对3株致病菌细胞对数期代时的影响,同时研究不同浓度乳酸对大肠杆菌膜电位的影响。试验结果表明:乳酸对3株食源性致病菌均有不同程度的抑制作用,并得出最小抑菌浓度(MIC)及最小杀菌浓度(MBC),分别是金黄色葡萄球菌MIC1.8mg/mL,MBC3.6mg/mL;蜡样芽孢杆菌MIC3.6mg/mL,MBC7.2mg/mL;大肠杆菌MIC0.9mg/mL,MBC1.8mg/mL;乳酸在最小抑菌浓度下显著(p≤0.05)延长了3株食源性致病菌对数生长期的代时,大肠杆菌对乳酸的敏感性较强,代时增加128%。采用流式细胞仪测定大肠杆菌的膜电位,发现乳酸对大肠杆菌细胞膜电位有一定的影响,随着乳酸浓度的增加,细胞膜电位逐渐增加,导致细胞的超极化程度越来越严重直至细胞死亡。

Three strains of food-borne pathogenic micro organisms, Escherichia coli, Staphylococcus aureus and Bacillus cereus, were selected for antibacterial and bactericide activity of lactic acid. The growth of food- borne pathogenic bacteria was inhibited in the presence of the lactic acid. Minimal inhibitory concentrations （MIC） and minimal bactericide concentration of lactic acid were determined. Lactic acid MIC and MBC values for the tested strains were as follows： 1.8 mg/mL（MIC）, 3.6 mg/mL（MBC）; 3.6 mg/mL（MIC）, 7.2 mg/mL（MBC）; 0.9 mg/mL（MIC）, 1.8 mg/mL （MBC） for Staphylococcus aureus, Bacillus cereus, Escherichia coli, respectively. The generation time of three strains was also determined. In the presence of the lactic acid, an increase of the generation time was observed for all the tested strains. Escherichia coli was the most sensitive strain showing an increase of the generation time by 128%. Flow cytometry has been used to study antibiotic effects of lactic acid on Escherichia coli membrane potential （MP）. Lactic acid has an effect on the Escherichia coli membrane potential. An increase in the magnitude of MP was observed with the increase of the lactic acid Concentration.