Department of Applied Chemistry and Microbiology, University of Helsinki, Biocenter 1, Viikinkaari 9, Helsinki, Finland.
Food Microbiol. 2010 May;27(3):347-55. doi: 10.1016/j.fm.2009.11.004. Epub 2009 Dec 1.
Survival of Bacillus cereus spores of dairy silo tank origin was investigated under conditions simulating those in operational dairy silos. Twenty-three strains were selected to represent all B. cereus isolates (n = 457) with genotypes (RAPD-PCR) that frequently colonised the silo tanks of at least two of the sampled eight dairies. The spores were studied for survival when immersed in liquids used for cleaning-in-place (1.0% sodium hydroxide at pH 13.1, 75 degrees C; 0.9% nitric acid at pH 0.8, 65 degrees C), for adhesion onto nonliving surfaces at 4 degrees C and for germination and biofilm formation in milk. Four groups with different strategies for survival were identified. First, high survival (log 15 min kill < or =1.5) in the hot-alkaline wash liquid. Second, efficient adherence of the spores to stainless steel from cold water. Third, a cereulide producing group with spores characterised by slow germination in rich medium and well preserved viability when exposed to heating at 90 degrees C. Fourth, spores capable of germinating at 8 degrees C and possessing the cspA gene. There were indications that spores highly resistant to hot 1% sodium hydroxide may be effectively inactivated by hot 0.9% nitric acid. Eight out of the 14 dairy silo tank isolates possessing hot-alkali resistant spores were capable of germinating and forming biofilm in whole milk, not previously reported for B. cereus.
研究了模拟操作中乳仓条件下的乳仓罐源蜡样芽孢杆菌孢子的存活情况。选择了 23 株菌来代表经常定植于 8 个采样乳品厂中至少 2 个乳品厂的罐内的所有蜡样芽孢杆菌分离株（n = 457）的基因型（RAPD-PCR）。研究了在用于原位清洁的液体（1.0%氢氧化钠，pH 值 13.1，75°C；0.9%硝酸，pH 值 0.8，65°C）中浸泡、4°C 下黏附于非生物表面以及在牛奶中发芽和形成生物膜时孢子的存活情况。确定了具有不同存活策略的 4 个组。首先，在热碱性洗涤液中有较高的存活能力（log 15 min 杀灭值≤1.5）。其次，孢子从冷水中有效地黏附于不锈钢表面。第三，产菌毒素的组，其在丰富的培养基中发芽缓慢，在 90°C 加热时保持较好的活力。第四，能够在 8°C 发芽且具有 cspA 基因的孢子。有迹象表明，对热 1%氢氧化钠具有高抗性的孢子可能会被热 0.9%硝酸有效地灭活。14 个具有耐热碱孢子的乳仓罐分离株中，有 8 个能够在全脂牛奶中发芽并形成生物膜，这是之前未报道过的蜡样芽孢杆菌的情况。
