Food Safety Programme, Institute of Environmental Science and Research Ltd (ESR), Christchurch Science Centre, PO Box 29-181, Ilam, Christchurch, New Zealand.
Food Microbiol. 2012 Dec;32(2):354-60. doi: 10.1016/j.fm.2012.07.015. Epub 2012 Aug 11.
Two bacterial isolates with inhibitory activity against Listeria monocytogenes and Enterococcus faecalis were obtained from soil. Genotypic and phenotypic characterization identified them as Enterococcus mundtii, a species whose ability to compete with L. monocytogenes is relatively unexplored compared to other members of the genus. The thermal stability of the inhibitory factor and its sensitivity to proteolytic enzymes indicate that it is most likely a bacteriocin. Both isolates grew at comparable rates to L. monocytogenes at 5 °C and 10 °C in vitro. One isolate killed L. monocytogenes when it reached concentrations of 10(6)-10(8) CFU ml(-1). Minimum inocula of 10(6) and 10(5) CFU ml(-1) of E. mundtii were required to reduce and maintain L. monocytogenes concentrations beneath the level of detection at 5 °C and 10 °C, respectively. In situ experiments at 5 °C showed that E. mundtii inhibited the growth of L. monocytogenes on vacuum-packed cold smoked salmon during its four week shelf life. E. mundtii could, therefore, control the growth of L. monocytogenes at low temperatures, indicating a potential application in controlling this pathogen in chilled foods. To control growth of Listeria, the concentration of E. mundtii needs to be high, but it is possible that a purified bacteriocin could be used to achieve the same effect.
从土壤中分离到两株具有抑制李斯特菌和粪肠球菌活性的细菌。通过基因型和表型特征鉴定，它们被确定为肠球菌 mundtii，与该属的其他成员相比，其与李斯特菌竞争的能力相对尚未得到探索。抑制因子的热稳定性及其对蛋白酶的敏感性表明，它很可能是一种细菌素。在体外，两种分离株在 5°C 和 10°C 时的生长速度与李斯特菌相当。当达到 10(6)-10(8)CFU ml(-1)浓度时，其中一个分离株可杀死李斯特菌。在 5°C 和 10°C 下，分别需要 10(6)和 10(5)CFU ml(-1)的最小接种量才能降低并保持李斯特菌浓度低于检测水平。在 5°C 的原位实验表明，肠球菌 mundtii 在真空包装的冷熏三文鱼的四周保质期内抑制了李斯特菌的生长。因此，肠球菌 mundtii 可以在低温下控制李斯特菌的生长，这表明它在控制冷藏食品中这种病原体方面具有潜在的应用。为了控制李斯特菌的生长，需要高浓度的肠球菌 mundtii，但也有可能使用纯化的细菌素来达到相同的效果。
