医院获得性感染（HAI）构成了影响全球数百万人的重大健康威胁，并增加了患者发病率和死亡率，仅在美国就产生了高达450亿美元的经济影响。革兰氏阴性菌尤其令人担忧，占所有HAI的30%以上，并且越来越具有多重耐药性。围绕HAI的这些普遍的健康问题促使ASHRAE等组织调查病原微生物库以及HVAC在HAI放大和传播中的作用。 （ASHRAE医院和诊所暖通空调设计手册）。本研究的目的是评估暖通空调系统在医院危重病人护理区域中的作用，作为医院获得性感染引起的机会性革兰氏阴性菌的潜在环境蓄水池。这项前瞻性介入性前后多中心试验在六家三级医院进行。总共对13个暖通空调系统进行微生物负荷取样。这些医院分别位于纽约（1）、密歇根（1）、宾夕法尼亚（2）和华盛顿（2）。 其目的是确定在暖通空调设备中安装紫外线杀菌辐射（UVGI）系统是否会减少暖通空调和患者护理环境中的微生物负荷，并导致危重患者呼吸机相关肺炎（VAP）的发病率降低。所有13个HVAC系统均显示存在革兰氏阴性菌，在UVGI干预之前，65种培养物中有65种检测呈阳性。其中假单胞菌占50.1%，不动杆菌占18%。5%的样本进行了培养。在UVGI干预90天后培养的65个样本显示菌落形成单位（CFU）减少了5对数。 纽约医院的其他研究表明，在高危队列中VAP的发病率降低。VAP的发病率从74%（n=31）下降到39%（n=18），每位患者的发作次数减少（对照组:UVGI干预前1.2次，UVGI干预后0.4次）。（Ryan等人）引用:ASHRAE论文CD:2014 ASHRAE冬季会议，纽约

Hospital Acquired Infections (HAIs) constitute a major health threat impacting millions of people globally, and increase patient morbidity and mortality with an economic impact of up to $45 billion in the US alone. Gram negative bacteria are of particular concern, are responsible for more than 30% of all HAIs and are becoming increasingly multi-drug resistant. These universal health concerns surrounding HAIs have driven organizations such as ASHRAE to investigate reservoirs of pathogenic microorganisms and the role of the HVAC in the amplification and transmission of HAIs. (ASHRAE HVAC Design Manual for Hospitals and Clinics).The objective of this study was to evaluate the role of HVAC systems serving hospital critical patient care areas, as potential environmental reservoirs for opportunistic Gram negative bacteria attributed to Hospital Acquired Infections. This prospective interventional pre and post multi-center trial was conducted in six tertiary care hospitals. A total of thirteen HVAC systems were sampled for microbial loads. The hospitals were located in New York (1), Michigan (1), Pennsylvania (2) and Washington, DC (2). was An aim was to determine if the installation of Ultraviolet Germicidal Irradiation (UVGI) systems in the HVAC equipment would reduce HVAC and patient care environment microbial loads and lead to reduced incidence of Ventilator Associated Pneumonia (VAP) in critically ill patients. All thirteen HVAC systems demonstrated the presence of gram negative bacteria with 65 of 65 cultures testing positive prior to UVGI intervention. Pseudomonas species was isolated in 50.1% and Acinetobacter species in18.5% of samples cultured. The 65 samples that were cultured 90 days post UVGI intervention demonstrated a 5 log reduction in colony forming units (CFU). Additional studies by the New York hospital demonstrated a reduced incidence of VAP in a high risk cohort. The Incidence of VAP fell from 74% (n=31) to 39% (n=18) and the number of episodes per patient decreased (control: 1.2 pre UVGI intervention to 0.4 post UVGI intervention). (Ryan et al)