Abstract：
Legionella pneumophila, the leading cause of Legionnaires\' disease in the United States, is found in lakes, ponds, and streams but poses a health risk when it grows in building water systems. The growth of L. pneumophila in hot water systems of healthcare facilities poses a significant risk to patients, staff, and visitors. Hospitals and long-term care facilities account for 76% of reported Legionnaires\' disease cases with mortality rates of 25%. Controlling L. pneumophila growth in hot water systems serving healthcare and hospitality buildings is currently achieved primarily by adding oxidizing chemical disinfectants. Chemical oxidants generate disinfection byproducts and can accelerate corrosion of premise plumbing materials and equipment. Alternative control methods that do not generate hazardous disinfection byproducts or accelerate corrosion are needed. L. pneumophila is an obligate aerobe that cannot sustain cellular respiration, amplify, or remain culturable when dissolved oxygen (DO) concentrations are too low (< 0.3 mg/L). An alternative method of controlling L. pneumophila growth by reducing DO levels in a hot water model system using a gas transfer membrane contactor was evaluated. A hot water model system was constructed and inoculated with L. pneumophila at DO concentrations above 0.5 mg/L. Once the model system was colonized, DO levels were incrementally reduced. Water samples were collected each week to evaluate the effect of reducing dissolved oxygen levels when all other conditions favored Legionella amplification. At DO concentrations below 0.3 mg/L, L. pneumophila concentrations were reduced by 1-log over 7 days. Under conditions in the hot water model system, at favorable temperatures and with no residual chlorine disinfectant, L. pneumophila concentrations were reduced by 1-log, indicating growth inhibition by reducing DO levels as the sole control measure. In sections of the model system where DO levels were not lowered L. pneumophila continued to grow. Reducing dissolved oxygen levels in hot water systems of healthcare and other large buildings to control L. pneumophila could also lower the risk of supplemental chemical treatment methods currently in use.
摘要：
嗜肺军团菌,美国军团病的主要病因，在湖泊中被发现，池塘,和溪流，但当它在建筑供水系统中生长时，会带来健康风险。在医疗保健设施的热水系统中，肺炎杆菌的生长对患者构成了重大风险，工作人员,和游客。医院和长期护理机构占报告的军团病病例的76%，死亡率为25%。目前，主要通过添加氧化性化学消毒剂来控制为医疗保健和酒店建筑服务的热水系统中的嗜肺乳杆菌生长。化学氧化剂会产生消毒副产物，并加速腐蚀前提管道材料和设备。需要不产生有害的消毒副产物或加速腐蚀的替代控制方法。嗜肺乳杆菌是一种不能维持细胞呼吸的专性气溶胶，放大，或在溶解氧（DO）浓度太低（<0.3mg/L）时保持可培养。评估了通过使用气体转移膜接触器降低热水模型系统中的DO水平来控制嗜肺乳杆菌生长的替代方法。构建了一个热水模型系统，并在DO浓度高于0.5mg/L时接种了嗜肺乳杆菌。一旦模型系统被殖民，DO水平逐渐降低。每周收集水样以评估当所有其他条件有利于军团菌扩增时降低溶解氧水平的效果。在DO浓度低于0.3mg/L时，嗜肺乳杆菌浓度在7天内降低1-log。在热水模型系统的条件下，在有利的温度下，没有残留的氯消毒剂，肺炎支原体浓度降低1-log，通过降低DO水平作为唯一的控制措施来指示生长抑制。在DO水平未降低的模型系统的部分中,嗜肺菌继续生长。降低医疗保健和其他大型建筑物的热水系统中的溶解氧水平以控制肺炎支原体也可以降低目前使用的补充化学处理方法的风险。
