Blatt S P, Parkinson M D, Pace E, Hoffman P, Dolan D, Lauderdale P, Zajac R A, Melcher G P
Department of Infectious Disease, Wilford Hall USAF Medical Center, Lackland Air Force Base, Texas 78236-5300.
Am J Med. 1993 Jul;95(1):16-22. doi: 10.1016/0002-9343(93)90227-g.
Nosocomial Legionnaires' disease remains a significant problem with many unresolved questions regarding transmission of legionella organisms to patients. We performed a case-control and environmental study to identify risk factors and modes of transmission of Legionella infection during an outbreak of nosocomial Legionnaires' disease in a military medical center.
During the calendar year 1989, 14 cases of nosocomial Legionnaires' disease were identified by active surveillance following the discovery of 2 culture-proven cases among organ transplant recipients. Four control patients were matched to each case by age, sex, and date of admission. Cases and controls were compared with respect to past medical history and hospital exposure variables. Odds ratios (ORs) and 95% confidence intervals (CIs) were calculated for matched variables. Environmental culturing of air and water supplies in and around the medical center was also performed.
The case-control study revealed the following significant risk factors for the acquisition of nosocomial Legionnaires' disease: immunosuppressive therapy (OR = 32.7, CI = 4.5 to 302.6), nasogastric tube use (OR = 18.4, CI = 2.6 to 166.2), bedbathing (OR = 10.7, CI = 2.2 to 59.0), and antibiotic therapy (OR = 14.6, CI = 2.9 to 84.4). Shower use (OR = 0.1, CI = 0 to 0.4) appeared to be a negative risk factor. Water cultures revealed Legionella pneumophila serogroup 1, monoclonal antibody subtype Philadelphia (identical to all patient isolates) in the ground-water supply to the hospital, 1 hot-water tank, and 15% of 85 potable water sites tested. Air sampling of cooling towers, hospital air intakes, and medical air and oxygen supplies were negative for Legionella organisms.
This study confirms the importance of potable water in transmitting nosocomial Legionnaires' disease and suggests that the organism gains access to the hospital via external water supplies. The risk factors identified in this case-control study provide evidence that Legionnaires' disease may act as a superinfection in a nosocomial setting and is likely acquired by aspiration, similar to other nosocomial pneumonias.
医院获得性军团病仍然是一个重大问题，关于军团菌向患者传播存在许多未解决的问题。我们进行了一项病例对照和环境研究，以确定一家军事医疗中心医院获得性军团病暴发期间军团菌感染的危险因素和传播方式。
1989年全年，在器官移植受者中发现2例经培养证实的病例后，通过主动监测确定了14例医院获得性军团病病例。按年龄、性别和入院日期为每个病例匹配4名对照患者。比较病例组和对照组的既往病史和医院暴露变量。计算匹配变量的比值比（OR）和95%置信区间（CI）。还对医疗中心及其周边的空气和供水进行了环境培养。
病例对照研究揭示了医院获得性军团病的以下重要危险因素：免疫抑制治疗（OR = 32.7，CI = 4.5至302.6）、使用鼻胃管（OR = 18.4，CI = 2.6至166.2）、床上擦浴（OR = 10.7，CI = 2.2至59.0）和抗生素治疗（OR = 14.6，CI = 2.9至84.4）。淋浴使用（OR = 0.1，CI = 0至0.4）似乎是一个负性危险因素。水培养显示医院的地下水供应、1个热水箱以及85个饮用水采样点中的15%检测到嗜肺军团菌血清1型、费城单克隆抗体亚型（与所有患者分离株相同）。对冷却塔、医院进气口以及医疗空气和氧气供应进行的空气采样未检测到军团菌。
本研究证实了饮用水在传播医院获得性军团病中的重要性，并表明该病原体通过外部供水进入医院。本病例对照研究确定的危险因素提供了证据，表明军团病可能在医院环境中作为一种二重感染，并且很可能与其他医院获得性肺炎一样通过误吸获得。
