Millette M, Luquet F M, Lacroix M
INRS-Institut Armand-Frappier, Research Laboratories in Sciences Applied to Food, Canadian Irradiation Centre, Laval, Quebec, Canada.
Lett Appl Microbiol. 2007 Mar;44(3):314-9. doi: 10.1111/j.1472-765X.2006.02060.x.
Food-borne pathogen inhibition was tested in the presence of a mixture of Lactobacillus acidophilus and Lactobacillus casei during fermentation under controlled pH conditions.
The growth of Escherichia coli O157:H7, Salmonella serotype Typhimurium, Staphylococcus aureus, Listeria innocua, Enterococcus faecium and Enterococcus faecalis was evaluated for 48 h at 37 degrees C. In the presence of the lactic acid bacteria (LAB), an increase of the generation time was observed for all the gram-positive bacteria evaluated. Staphylococcus aureus was the most sensitive strain showing an increase of the generation time by 210%. However, for all the gram-negative bacteria evaluated, no inhibition occurred after 8 h of fermentation. The soluble portion of Lact. acidophilus- and Lact. casei-fermented milk was recuperated and tested for its antimicrobial activity. Listeria innocua and Staph. aureus were the most sensitive to the presence of fermented milk supernatant showing an inhibition of 85.9% and 84.7%, respectively. This soluble fraction was neutralized to eliminate the antimicrobial effect of the organic acids produced; the most sensitive strains were L. innocua and E. coli O157:H7 showing an inhibition of 65.9% and 61.9%, respectively. Finally, the soluble fraction was neutralized and irradiated at 45 kGy using a (60)Co source to eliminate the possible antimicrobial effect of both organic acids and bacteriocin-like substances. Enterococcus faecalis, E. coli O157:H7 and Staph. aureus were the most affected bacteria by this fraction, showing 39.1, 32 and 31.2% inhibition, respectively.
The results obtained in this study suggest the implication of both organic acids and bacteriocin-like inhibitory substances in the antimicrobial activity observed in the soluble fraction of the probiotic preparation.
This study revealed the antimicrobial mechanisms of action of Lact. acidophilus- and Lact. casei-fermented milk used to prevent antibiotic-associated diarrhoea.
在受控pH条件下发酵过程中，检测嗜酸乳杆菌和干酪乳杆菌混合物存在时对食源性病原体的抑制作用。
在37℃下对大肠杆菌O157:H7、鼠伤寒沙门氏菌、金黄色葡萄球菌、无害李斯特菌、粪肠球菌和屎肠球菌的生长进行了48小时评估。在乳酸菌（LAB）存在的情况下，所评估的所有革兰氏阳性菌的代时均有所增加。金黄色葡萄球菌是最敏感的菌株，代时增加了210%。然而，对于所评估的所有革兰氏阴性菌，发酵8小时后未出现抑制作用。回收嗜酸乳杆菌和干酪乳杆菌发酵乳的可溶部分，并检测其抗菌活性。无害李斯特菌和金黄色葡萄球菌对发酵乳上清液的存在最为敏感，抑制率分别为85.9%和84.7%。将该可溶部分中和以消除所产生有机酸的抗菌作用；最敏感的菌株是无害李斯特菌和大肠杆菌O157:H7，抑制率分别为65.9%和61.9%。最后，将可溶部分中和并用钴-60源在45千戈瑞下辐照，以消除有机酸和类细菌素物质可能的抗菌作用。粪肠球菌、大肠杆菌O157:H7和金黄色葡萄球菌受该部分影响最大，抑制率分别为39.1%、32%和31.2%。
本研究获得的结果表明，有机酸和类细菌素抑制物质均参与了益生菌制剂可溶部分中观察到的抗菌活性。
本研究揭示了用于预防抗生素相关性腹泻的嗜酸乳杆菌和干酪乳杆菌发酵乳的抗菌作用机制。
