We report the existence and resuscitation of viable but nonculturable (VBNC) Escherichia coli O157:H7 cells in drinking water induced by the common point-of-use disinfection treatments of boiling or microwaving. Tap water and saline samples containing E. coli O157:H7 culturable cells from a bovine isolate or two clinical isolates were boiled (1, 10, or 15 min) on a hot plate or microwaved (1.5 min) to reach boiling. No culturable E. coli O157:H7 cells were observed in the treated samples using conventional plating methods. In samples boiled for 1 or 10 min, two viability assays separately detected that 2–5.5% of the cells retained an intact membrane, while 28 to 87 cells out of the initial 10⁸ cells retained both measurable intracellular esterase activity and membrane integrity. In samples boiled for 15 min, no viable cells were detected. The microwaved samples contained 6–10% of cells with an intact membrane, while 21 to 108 cells out of the initial 10⁸ cells retained both membrane integrity and esterase activity. The number of viable cells retaining both metabolic activity and membrane integrity were consistent in all samples, supporting the survival of a small number of E. coli O157:H7 cells in the VBNC state after boiling for 1 or 10 min or microwaving. Furthermore, the VBNC E. coli O157:H7 cells regained growth at 37 °C in culture media containing autoinducers produced by common non-pathogenic E. coli, commonly present in the human intestine, and norepinephrine. The resuscitated cells were culturable on conventional plates and expressed mRNA encoding the E. coli O157 lipopolysaccharide gene (rfbE) and the H7 flagellin gene (fliC). This study highlights potential concerns for public health risk management of VBNC E. coli O157:H7 in drinking water disinfected by heat treatment at point-of-use. The public health significance of these concerns warrants further investigation.

我们报告了由煮沸或微波加热的常见使用点消毒处理诱导的饮用水中有活力但不可培养的（VBNC）大肠杆菌O157：H7细胞的存在和复苏。将含有来自牛分离株或两个临床分离株的大肠杆菌O157：H7可培养细胞的自来水和盐水样品在热板上煮沸（1、10或15分钟），或微波加热（1.5分钟）以达到沸腾状态。使用常规接种方法在处理的样品中未观察到可培养的大肠杆菌O157：H7细胞。在煮沸1或10分钟的样品中，两次活力检测分别检测到2–5.5％的细胞保留了完整的膜，而最初10 ^8个细胞中有28至87个细胞 细胞保留了可测量的细胞内酯酶活性和膜完整性。煮沸15分钟的样品中未检测到活细胞。微波样品含有6-10％的具有完整膜的细胞，而最初的10 ^8个 细胞中有21至108个细胞保留了膜的完整性和酯酶活性。保留代谢活性和膜完整性的活细胞数量在所有样品中均保持一致，支持煮沸1分钟或10分钟或微波后，少数VBNC状态的大肠杆菌O157：H7细胞存活。此外，VBNC大肠杆菌O157：H7细胞在含有普通非致病性大肠杆菌产生的自体诱导剂的培养基中，于37°C恢复生长。，通常存在于人体肠道和去甲肾上腺素。复苏的细胞可在常规平板上培养，并表达编码大肠杆菌O157脂多糖基因（rfbE）和H7鞭毛蛋白基因（fliC）的mRNA 。这项研究突出了在使用点通过热处理消毒的饮用水中VBNC大肠杆菌O157：H7对公共健康风险管理的潜在问题。这些关注的公共卫生意义值得进一步调查。