Trias Rosalia, Badosa Esther, Montesinos Emilio, Bañeras Lluís
Institute of Food and Agricultural Technology-CeRTA, CIDSAV, University of Girona, Campus Montilivi 17071, Girona, Spain.
Int J Food Microbiol. 2008 Sep 30;127(1-2):91-8. doi: 10.1016/j.ijfoodmicro.2008.06.011. Epub 2008 Jun 18.
Ten Leuconostoc mesenteroides and one Ln. citreum strains isolated from fresh fruit and vegetables were tested for their antagonistic capacity against Listeria monocytogenes. Genetic differences among strains were analyzed by Random Amplified Polymorphic DNA (RAPD). All the isolates clustered together and differed from the type strain Ln. mesenteroides ATCC 8293 as well as from Ln. fallax and Ln. citreum. Organic acids, hydrogen peroxide and bacteriocins were detected as main inhibition mechanisms. Characterization of culture supernatants from the bacteriocinogenic strains, CM135 and CM160 revealed a high resistance of antibacterial activity to temperature and pH, and a bactericidal mode of action against L. monocytogenes. Produced bacteriocins belonged to the Class IIa and sequencing of genes showed complete homology with mesentericin Y105. A study of the effect of the relative dose of pathogen and LAB on control of L. monocytogenes in wounds of Golden Delicious apples and Iceberg lettuce leaf cuts was performed. A comparison of the dose of bioprotective strain needed for a ten fold reduction of the viable pathogen concentration (ED90) revealed that strain CM160 was the most effective against L. monocytogenes. ED90 values varied from 1.3.10(4) to 5.0.10(5) cfu.g(-1) or wound, at ranges of pathogen levels from 1.0.10(3) to 5.0.10(4) cfu.g(-1) of lettuce or wound of apple. The efficiency of the strains was also calculated as the ratio of the ED90 value to the pathogen dose inoculated. The lowest ratio was found for strain CM160 at 5 to 50 cells of LAB per cell of pathogen. The strain offers potential application for prevention of the presence of L. monocytogenes in fresh fruit and vegetables.
对从新鲜水果和蔬菜中分离出的10株肠系膜明串珠菌和1株柠檬明串珠菌菌株进行了针对单核细胞增生李斯特菌的拮抗能力测试。通过随机扩增多态性DNA（RAPD）分析菌株之间的遗传差异。所有分离株聚在一起，与肠系膜明串珠菌模式菌株ATCC 8293以及类明串珠菌和柠檬明串珠菌不同。检测到有机酸、过氧化氢和细菌素是主要抑制机制。对产细菌素菌株CM135和CM160的培养上清液进行表征，结果显示其抗菌活性对温度和pH具有高耐受性，并且对单核细胞增生李斯特菌具有杀菌作用方式。产生的细菌素属于IIa类，基因测序显示与肠膜菌素Y105完全同源。进行了一项关于病原体和乳酸菌相对剂量对金冠苹果伤口和卷心莴苣叶片切口处单核细胞增生李斯特菌控制效果的研究。对使活菌病原体浓度降低10倍所需的生物保护菌株剂量（ED90）进行比较，结果显示菌株CM160对单核细胞增生李斯特菌最有效。在生菜或苹果伤口的病原体水平范围为1.0×10³至5.0×10⁴ cfu·g⁻¹时，ED90值在1.3×10⁴至5.0×10⁵ cfu·g⁻¹或伤口之间变化。还计算了菌株的效率，即ED90值与接种病原体剂量的比值。在每细胞病原体对应5至50个乳酸菌细胞时，菌株CM160的比值最低。该菌株在预防新鲜水果和蔬菜中单核细胞增生李斯特菌的存在方面具有潜在应用价值。
