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)