Sharma M, Ryu J-H, Beuchat L R
Center for Food Safety and Department of Food Science and Technology, University of Georgia, 1109 Experiment Street, Griffin, GA 30223-1797, USA.
J Appl Microbiol. 2005;99(3):449-59. doi: 10.1111/j.1365-2672.2005.02659.x.
To determine the effectiveness of an alkaline cleaner used in food-processing plants and a lytic bacteriophage specific for Escherichia coli O157:H7 in killing wild type and rpoS-deficient cells of the pathogen in a biofilm.
Wild type and rpoS-deficient cells were attached to stainless steel coupons (c. 7-8 log CFU per coupon) on which biofilms were developed during incubation at 22 degrees C for 96 h in M9 minimal salts media (MSM) with one transfer to fresh medium. Coupons were treated with 100 and 25% working concentrations of a commercial alkaline cleaner (pH 11.9, with 100 microg ml(-1) free chlorine) used in the food industry, chlorine solutions (50 and 100 microg ml(-1) free chlorine), or sterile deionized water (control) at 4 degrees C for 1 and 3 min. Treatment with 100% alkaline cleaners reduced populations by 5-6 log CFU per coupon, a significant (P < or = 0.05) reduction compared with treatment with water. Initial populations (2.6 log CFU per coupon) of attached cells of both strains were reduced by 1.2 log CFU per coupon when treated with bacteriophage KH1 (7.7 log PFU ml(-1)) for up to 4 days at 4 degrees C. Biofilms containing low populations (2.7-2.8 log CFU per coupon) of wild type and rpoS-deficient cells that had developed for 24 h at 22 degrees C were not decreased by more than 1 log CFU per coupon when treated with KH1 (7.5 log PFU ml(-1)) at 4 degrees C.
Higher numbers of cells of E. coli O157:H7 in biofilms are killed by treatment with an alkaline cleaner than with hypochlorite alone, possibly through a synergistic mechanism of alkaline pH and hypochlorite. Populations of cells attached on coupons were reduced by treating with bacteriophage but cells enmeshed in biofilms were protected.
The alkaline pH, in combination with hypochlorite, in a commercial cleaner is responsible for killing E. coli O157:H7 in biofilms. Treatment with bacteriophage KH1 reduces populations of cells attached to coupon surfaces but not cells in biofilms.
确定食品加工厂使用的一种碱性清洁剂以及一种针对大肠杆菌O157:H7的裂解性噬菌体在杀死生物膜中该病原体的野生型和rpoS缺陷型细胞方面的有效性。
将野生型和rpoS缺陷型细胞附着于不锈钢试片（每个试片约7 - 8 log CFU）上，在含有M9基本盐培养基（MSM）的条件下于22℃孵育96小时以形成生物膜，期间转移至新鲜培养基一次。将试片在4℃下用食品工业中使用的一种商业碱性清洁剂（pH 11.9，含100 μg ml⁻¹游离氯）的100%和25%工作浓度、氯溶液（50和100 μg ml⁻¹游离氯）或无菌去离子水（对照）处理1分钟和3分钟。用100%碱性清洁剂处理使每个试片上的菌数减少5 - 6 log CFU，与用水处理相比有显著（P≤0.05）减少。当在4℃用噬菌体KH1（7.7 log PFU ml⁻¹）处理长达4天时，两种菌株附着细胞的初始菌数（每个试片2.6 log CFU）减少了1.2 log CFU/试片。在22℃培养24小时形成的含有低菌数（每个试片2.7 - 2.8 log CFU）野生型和rpoS缺陷型细胞的生物膜，在4℃用KH1（7.5 log PFU ml⁻¹）处理时，每个试片的菌数减少不超过1 log CFU。
与单独使用次氯酸盐相比，用碱性清洁剂处理可杀死生物膜中更多数量的大肠杆菌O157:H7细胞，可能是通过碱性pH值和次氯酸盐的协同机制。用噬菌体处理可减少附着在试片上的细胞菌数，但包裹在生物膜中的细胞受到保护。
商业清洁剂中的碱性pH值与次氯酸盐结合可杀死生物膜中的大肠杆菌O157:H7。用噬菌体KH1处理可减少附着在试片表面的细胞菌数，但不能减少生物膜中的细胞菌数。
