Zimmer-Thomas J L, Slawson R M, Huck P M
Department of Biology, University of Waterloo, Waterloo, Ontario, Canada.
J Water Health. 2007 Sep;5(3):407-15. doi: 10.2166/wh.2007.036.
DNA repair and survival of pathogenic E. coli O157:H7 was investigated following exposure to ultraviolet (UV) radiation from both low-pressure (LP) and medium-pressure (MP) lamps. This study included irradiation at UV doses used in drinking water treatment and lower doses indicative of potential treatment problems. Immediately following UV exposure, an average log inactivation of 4.5 or greater was observed following all tested doses of LP (5, 8, 20 and 40 mJ/cm(2)) or MP UV (5 and 8 mJ/cm(2)) indicating the sensitivity of E. coli O157:H7 to UV irradiation. Following conditions conducive to repair, maximum photo repair occurred rapidly within 30 minutes after low doses (5 and 8 mJ/cm(2)) of LP UV. The rate of repair was much higher than reported previously in non-pathogenic E. coli (which occurred within 2 hours). In contrast to LP UV, limited photo repair of E. coli O157:H7 was observed following MP UV exposure at reduced doses (5 and 8 mJ/cm(2)). At these lower doses, low levels of light independent repair were observed following LP UV, but not following exposure of MP UV irradiation. This study indicates that MP UV may enhance UV disinfection of E. coli O157:H7 by reducing the ability to repair following non-ideal treatment conditions. Following doses used in drinking water treatment (20 and 40 mJ/cm(2)), low levels of photo repair following LP UV were evident.
研究了致病性大肠杆菌O157:H7在暴露于低压（LP）和中压（MP）灯发出的紫外线（UV）辐射后的DNA修复和存活情况。本研究包括饮用水处理中使用的紫外线剂量以及表明潜在处理问题的较低剂量的辐照。紫外线暴露后，在所有测试的LP紫外线剂量（5、8、20和40 mJ/cm²）或MP紫外线剂量（5和8 mJ/cm²）下，立即观察到平均对数失活率为4.5或更高，这表明大肠杆菌O157:H7对紫外线辐照敏感。在有利于修复的条件下，低剂量（5和8 mJ/cm²）的LP紫外线照射后30分钟内迅速发生最大光修复。修复速率比先前报道的非致病性大肠杆菌（在2小时内发生）高得多。与LP紫外线相反，在MP紫外线低剂量（5和8 mJ/cm²）照射后，观察到大肠杆菌O157:H7的光修复有限。在这些较低剂量下，LP紫外线照射后观察到低水平的光独立修复，但MP紫外线照射后未观察到。本研究表明，MP紫外线可能通过降低非理想处理条件下的修复能力来增强大肠杆菌O157:H7的紫外线消毒效果。在饮用水处理中使用的剂量（20和40 mJ/cm²）下，LP紫外线照射后的光修复水平较低是明显的。
