PDF(Pubmed)
Abstract：
In contrast to \"frank\" pathogens, like Salmonella entrocolitica, Shigella dysenteriae, and Vibrio cholerae, that always have a probability of disease, \"opportunistic\" pathogens are organisms that cause an infectious disease in a host with a weakened immune system and rarely in a healthy host. Historically, drinking water treatment has focused on control of frank pathogens, particularly those from human or animal sources (like Giardia lamblia, Cryptosporidium parvum, or Hepatitis A virus), but in recent years outbreaks from drinking water have increasingly been due to opportunistic pathogens. Characteristics of opportunistic pathogens that make them problematic for water treatment include: (1) they are normally present in aquatic environments, (2) they grow in biofilms that protect the bacteria from disinfectants, and (3) under appropriate conditions in drinking water systems (e.g., warm water, stagnation, low disinfectant levels, etc.), these bacteria can amplify to levels that can pose a public health risk. The three most common opportunistic pathogens in drinking water systems are Legionella pneumophila, Mycobacterium avium, and Pseudomonas aeruginosa. This report focuses on these organisms to provide information on their public health risk, occurrence in drinking water systems, susceptibility to various disinfectants, and other operational practices (like flushing and cleaning of pipes and storage tanks). In addition, information is provided on a group of nine other opportunistic pathogens that are less commonly found in drinking water systems, including Aeromonas hydrophila, Klebsiella pneumoniae, Serratia marcescens, Burkholderia pseudomallei, Acinetobacter baumannii, Stenotrophomonas maltophilia, Arcobacter butzleri, and several free-living amoebae including Naegleria fowleri and species of Acanthamoeba. The public health risk for these microbes in drinking water is still unclear, but in most cases, efforts to manage Legionella, mycobacteria, and Pseudomonas risks will also be effective for these other opportunistic pathogens. The approach to managing opportunistic pathogens in drinking water supplies focuses on controlling the growth of these organisms. Many of these microbes are normal inhabitants in biofilms in water, so the attention is less on eliminating these organisms from entering the system and more on managing their occurrence and concentrations in the pipe network. With anticipated warming trends associated with climate change, the factors that drive the growth of opportunistic pathogens in drinking water systems will likely increase. It is important, therefore, to evaluate treatment barriers and management activities for control of opportunistic pathogen risks. Controls for primary treatment, particularly for turbidity management and disinfection, should be reviewed to ensure adequacy for opportunistic pathogen control. However, the major focus for the utility\'s opportunistic pathogen risk reduction plan is the management of biological activity and biofilms in the distribution system. Factors that influence the growth of microbes (primarily in biofilms) in the distribution system include, temperature, disinfectant type and concentration, nutrient levels (measured as AOC or BDOC), stagnation, flushing of pipes and cleaning of storage tank sediments, and corrosion control. Pressure management and distribution system integrity are also important to the microbial quality of water but are related more to the intrusion of contaminants into the distribution system rather than directly related to microbial growth. Summarizing the identified risk from drinking water, the availability and quality of disinfection data for treatment, and guidelines or standards for control showed that adequate information is best available for management of L. pneumophila. For L. pneumophila, the risk for this organism has been clearly established from drinking water, cases have increased worldwide, and it is one of the most identified causes of drinking water outbreaks. Water management best practices (e.g., maintenance of a disinfectant residual throughout the distribution system, flushing and cleaning of sediments in pipelines and storage tanks, among others) have been shown to be effective for control of L. pneumophila in water supplies. In addition, there are well documented management guidelines available for the control of the organism in drinking water distribution systems. By comparison, management of risks for Mycobacteria from water are less clear than for L. pneumophila. Treatment of M. avium is difficult due to its resistance to disinfection, the tendency to form clumps, and attachment to surfaces in biofilms. Additionally, there are no guidelines for management of M. avium in drinking water, and one risk assessment study suggested a low risk of infection. The role of tap water in the transmission of the other opportunistic pathogens is less clear and, in many cases, actions to manage L. pneumophila (e.g., maintenance of a disinfectant residual, flushing, cleaning of storage tanks, etc.) will also be beneficial in helping to manage these organisms as well.
摘要：
与“弗兰克”病原体相反，比如内大肠杆菌沙门氏菌,痢疾志贺氏菌,和霍乱弧菌,总是有疾病的可能性，“机会性”病原体是在免疫系统减弱的宿主中引起传染病的生物体，很少在健康宿主中引起传染病。历史上,饮用水处理的重点是控制弗兰克病原体，特别是那些来自人类或动物的来源(如贾第鞭毛虫，微小隐孢子虫,或甲型肝炎病毒)，但是近年来，饮用水的爆发越来越多地归因于机会病原体。使它们成为水处理问题的机会病原体的特征包括：（1）它们通常存在于水生环境中，（2）它们生长在生物膜中，保护细菌免受消毒剂的侵害，和(3)在饮用水系统的适当条件下(例如，温暖的水,停滞,低消毒剂水平，等。),这些细菌可以放大到可能构成公共健康风险的水平。饮用水系统中最常见的三种机会致病菌是嗜肺军团菌,鸟分枝杆菌,还有铜绿假单胞菌.本报告重点关注这些生物，以提供有关其公共卫生风险的信息，在饮用水系统中发生，对各种消毒剂的敏感性，和其他操作实践（如管道和储罐的冲洗和清洁）。此外,提供了关于饮用水系统中较不常见的九种其他机会病原体的信息，包括嗜水气单胞菌,肺炎克雷伯菌,粘质沙雷菌,假伯克霍尔德菌,鲍曼不动杆菌,嗜麦芽窄食单胞菌,Butzleri杆菌,和几种自由生活的变形虫，包括Naegleriafowleri和棘阿米巴。饮用水中这些微生物对公众健康的危害尚不清楚。但在大多数情况下,努力管理军团菌，分枝杆菌,和假单胞菌的风险也将对这些其他机会性病原体有效。管理饮用水供应中的机会病原体的方法侧重于控制这些生物的生长。这些微生物中有许多是水中生物膜中的正常居民，因此，注意力较少放在消除这些生物进入系统上，而更多的是管理它们在管网中的出现和浓度。随着与气候变化相关的预期变暖趋势，驱动饮用水系统中机会性病原体生长的因素可能会增加。这很重要,因此,评估治疗障碍和管理活动，以控制机会性病原体风险。初级治疗的控制，特别是浊度管理和消毒，应进行审查，以确保机会病原体控制的充分性。然而,公用事业公司的机会性病原体风险降低计划的主要重点是分配系统中生物活性和生物膜的管理。影响分布系统中微生物（主要在生物膜中）生长的因素包括，温度,消毒剂类型和浓度，营养水平（以AOC或BDOC衡量），停滞,管道的冲洗和储罐沉积物的清洁，和腐蚀控制。压力管理和分配系统完整性对水的微生物质量也很重要，但更多地与污染物侵入分配系统有关，而不是直接与微生物生长有关。总结已确定的饮用水风险，用于治疗的消毒数据的可用性和质量，和控制指南或标准表明，足够的信息是最好的管理肺炎克雷伯菌。对于肺炎支原体，这种生物的风险已经从饮用水中清楚地确定，世界各地的病例有所增加，它是饮用水爆发的最确定的原因之一。水管理最佳实践(例如，在整个分配系统中保持消毒剂残留，冲洗和清洁管道和储罐中的沉积物，除其他外）已被证明可有效控制供水中的嗜肺乳杆菌。此外,饮用水分配系统中的生物控制有充分的管理指南。相比之下,对水中分枝杆菌的风险管理不如对肺炎支原体的风险管理清楚。由于对消毒的抗性，鸟分枝杆菌的治疗是困难的，形成团块的趋势，并附着在生物膜的表面上。此外,饮用水中的鸟分枝杆菌没有管理指南，一项风险评估研究表明，感染风险较低。自来水在其他机会性病原体传播中的作用不太清楚，在许多情况下,管理肺炎支原体的行动(例如，保持消毒剂残留，冲洗,储罐的清洁，等。)也将有助于管理这些生物。
