食源性乳酸菌安全性的评价

从不同来源的样品中分离得到36 株乳酸菌，对其进行常见抗生素如氯霉素、四环素、红霉素抗药性分析，结果表明，26 株菌具有抗药性，其中4 株携带抗生素抗性基因，并且菌株Enterococcus faecium KN9所携带的四环素抗性基因tet（M）和tet（L）能通过接合作用，转移到受体菌Lactococcus lactis MG1614中。对这些乳酸菌产生有害代谢产物分析结果表明，部分菌株可以产生生物胺，所有的菌株都不产生硝基还原酶和偶氮还原酶。所以，本实验分离到的大部分乳酸菌是安全的，只有携带有抗四环素基因的E. faecium KN9具有潜在的安全隐患。因此，需要在食用前对乳酸菌进行安全性评价，以减少可能的安全隐患。

Safety Assessment of Lactic Acid Bacteria Isolated from Foods and Drugs

Totally 36 lactic acid bacteria (LAB) strains were isolated from different samples. The analysis of antibiotic
susceptibility showed that 26 strains of them were resistant to one or more antibiotic agents, and 4 of the 26 strains carried
antibiotic resistant genes. The tetracycline resistant genes tet (M) and tet (L), carried by Enterococcus faecium KN9 could
be transferred to the recipient Lactococcus lactis MG1614 by conjugation. We also assessed the ability of production of
undesirable metabolites, and the results showed that some of 36 isolates could produce tyramine or/and histamine, but none
of them could produce nitroreductase or azoreductase. Therefore, we could conclude that most of the isolates are safe, and
E. faecium KN9 carrying tetracycline resistance genes may be detrimental to human beings so that it is necessary to perform
safety assessment of lactic acid bacteria before they are applied.