Ryu Jee-Hoon, Beuchat Larry R
Center for Food Safety and Department of Food Science and Technology, University of Georgia, 1109 Experiment Street, Griffin, Georgia 30223-1797, USA.
J Food Prot. 2005 Dec;68(12):2614-22. doi: 10.4315/0362-028x-68.12.2614.
Biofilm formation by Bacillus cereus 038-2 on stainless steel coupons, sporulation in the biofilm as affected by nutrient availability, temperature, and relative humidity, and the resistance of vegetative cells and spores in biofilm to sanitizers were investigated. Total counts in biofilm formed on coupons immersed in tryptic soy broth (TSB) at 12 and 22 degrees C consisted of 99.94% of vegetative cells and 0.06% of spores. Coupons on which biofilm had formed were immersed in TSB or exposed to air with 100, 97, 93, or 85% relative humidity. Biofilm on coupons immersed in TSB at 12 degrees C for an additional 6 days or 22 degrees C for an additional 4 days contained 0.30 and 0.02% of spores, respectively, whereas biofilm exposed to air with 100 or 97% relative humidity at 22 degrees C for 4 days contained 10 and 2.5% of spores, respectively. Sporulation did not occur in biofilm exposed to 93 or 85% relative humidity at 22 degrees C. Treatment of biofilm on coupons that had been immersed in TSB at 22 degrees C with chlorine (50 microg/ml), chlorine dioxide (50 microg/ml), and a peroxyacetic acid-based sanitizer (Tsunami 200, 40 microg/ml) for 5 min reduced total cell counts (vegetative cells plus spores) by 4.7, 3.0, and 3.8 log CFU per coupon, respectively; total cell counts in biofilm exposed to air with 100% relative humidity were reduced by 1.5, 2.4, and 1.1 log CFU per coupon, respectively, reflecting the presence of lower numbers of vegetative cells. Spores that survived treatment with chlorine dioxide had reduced resistance to heat. It is concluded that exposure of biofilm formed by B. cereus exposed to air at high relative humidity (> or =97%) promotes the production of spores. Spores and, to a lesser extent, vegetative cells embedded in biofilm are protected against inactivation by sanitizers. Results provide new insights to developing strategies to achieve more effective sanitation programs to minimize risks associated with B. cereus in biofilm formed on food contact surfaces and on foods.
研究了蜡样芽孢杆菌038 - 2在不锈钢试片上的生物膜形成、生物膜中芽孢形成受营养可用性、温度和相对湿度的影响，以及生物膜中营养细胞和芽孢对消毒剂的抗性。浸于胰蛋白胨大豆肉汤（TSB）中在12℃和22℃形成的生物膜中，总菌数中营养细胞占99.94%，芽孢占0.06%。已形成生物膜的试片浸于TSB中或暴露于相对湿度为100%、97%、93%或85%的空气中。浸于12℃的TSB中再培养6天或22℃的TSB中再培养4天的试片上的生物膜，分别含有0.30%和0.02%的芽孢，而在22℃下暴露于相对湿度为100%或97%的空气中4天的生物膜，分别含有10%和2.5%的芽孢。在22℃下暴露于相对湿度为93%或85%的空气中的生物膜中未发生芽孢形成。用氯（50μg/ml）、二氧化氯（50μg/ml）和过氧乙酸基消毒剂（Tsunami 200，40μg/ml）处理浸于22℃的TSB中的试片上的生物膜5分钟，每片试片的总菌数（营养细胞加芽孢）分别减少4.7、3.0和3.8 log CFU；暴露于相对湿度为100%的空气中的生物膜中的总菌数，每片试片分别减少1.5、2.4和1.1 log CFU，这反映出其中营养细胞数量较少。经二氧化氯处理后存活的芽孢对热的抗性降低。得出结论，蜡样芽孢杆菌形成的生物膜暴露于高相对湿度（≥97%）的空气中会促进芽孢产生。生物膜中包埋的芽孢以及程度较轻的营养细胞受到保护，免受消毒剂的灭活。研究结果为制定更有效的卫生计划策略提供了新见解，以将与食品接触表面和食品上形成的生物膜中的蜡样芽孢杆菌相关的风险降至最低。
