Wilks Sandra A, Michels Harold T, Keevil C William
Environmental Healthcare Unit, School of Biological Sciences, University of Southampton, Bassett Crescent East, Southampton, SO16 7PX, UK.
Int J Food Microbiol. 2006 Sep 1;111(2):93-8. doi: 10.1016/j.ijfoodmicro.2006.04.037. Epub 2006 Jul 28.
Listeria monocytogenes is an important re-emerging pathogen which is commonly found in the environment. Many outbreaks have been associated with the contamination of food produce, often linked to cross-contamination from surfaces or equipment to prepared foodstuffs. In the present study a number of copper-base metal alloys have been used to assess the survival times of L. monocytogenes on different materials, in comparison with stainless steel. High concentrations (10(7)) of bacteria were placed on metal coupons cut from each alloy. After defined incubation times, coupons were placed in tubes containing phosphate buffered saline and vortexed to remove the cells. Aliquots were then plated onto tryptone blood agar plates and the number of colony forming units counted. The high concentration of bacteria was used to represent a "worst-case" scenario. The results indicate that survival is greatly reduced on a copper-base alloy compared to stainless steel. Viable cells could be detected on stainless steel after 24 h incubation at room temperature. On copper, brass, aluminium bronze and silicon bronze, no viable bacteria could be detected after 60 min incubation, indicating a 5 log reduction (the detection limit of the procedure was 100 bacteria). No cells could be detected from copper nickel and copper nickel zinc alloys, after 90 min incubation. The viability stain, 5-cyano-2,3-ditolyl tetrazolium chloride (CTC), confirmed these results, with actively respiring bacteria being clearly labelled on stainless steel after 24 h. The results suggest that careful choice of surface material could reduce the potential risk of cross-contamination in industrial, commercial and domestic environments.
单核细胞增生李斯特菌是一种重要的再度出现的病原体,在环境中普遍存在。许多疫情爆发都与食品污染有关,通常是由于表面或设备对即食食品的交叉污染。在本研究中,与不锈钢相比,使用了多种铜基金属合金来评估单核细胞增生李斯特菌在不同材料上的存活时间。将高浓度(10⁷)的细菌接种在从每种合金上切割下来的金属试片上。在规定的孵育时间后,将试片放入含有磷酸盐缓冲盐水的试管中,涡旋振荡以去除细胞。然后取等分试样接种到胰蛋白胨血琼脂平板上,计算菌落形成单位的数量。使用高浓度细菌代表“最坏情况”。结果表明,与不锈钢相比,在铜基金属合金上细菌的存活率大大降低。在室温下孵育24小时后,仍能在不锈钢上检测到活菌。在铜、黄铜、铝青铜和硅青铜上,孵育60分钟后未检测到活菌,表明细菌数量减少了5个对数级(该方法的检测限为100个细菌)。孵育90分钟后,在铜镍合金和铜镍锌合金上未检测到任何细胞。活性染料5-氰基-2,3-二苯基四氮唑氯化物(CTC)证实了这些结果,孵育24小时后,在不锈钢上能清晰地标记出活跃呼吸的细菌。结果表明,在工业、商业和家庭环境中,仔细选择表面材料可以降低交叉污染的潜在风险。