Biocontamination of surfaces in controlled environment rooms: The influence of environmental parameters and the design of the air conditioning system

Abstract

This research aims to evaluate the relationship between the environmental and design parameters of the air conditioning system, and the presence of colony-forming units (CFUs) of bacteria on surfaces. This retrospective study was carried out in controlled environment rooms in 12 hospitals in Spain, as part of a periodic environmental biosecurity assessment programme. Between 2010 and 2017, a total amount of 1027 samples were collected from floors and 861 from hand contact surfaces (HCSs), and the environmental parameters (temperature, relative humidity, fungal and bacterial CFUs present in the air) and design parameters (air changes per hour (ACH), differential pressure and position of the high efficiency particulate air filter) were monitored. The multivariate analysis concluded that, for each increased degree Celsius of temperature, the bacterial CFUs increased by 22.4% (incidence rate ratio (IRR): 1.224, 1.05–1.43) and by 25.9% (IRR: 1.259, 1.06–1.50) on HCSs and floors, respectively, and for each increase in ACH, the CFUs decreased 3.9% (IRR: 0.961, 0.94–0.99) and 2.5% (IRR: 0.975, 0.95–1.00) on HCSs and floors, respectively. Our results show the influence of the environmental and design parameters of air conditioning on the number of CFUs on surfaces and floors.

Relationship Between Airborne Fungi Presence and the Position of the High Efficiency Particulate Air Filter in the Heating, Ventilation, and Air Conditioning System

“…Temperature and relative humidity have a significant influence on the presence of microorganisms in the air and on surfaces (Eames et al, 2009; Fu Shaw et al, 2018; Sabuco-Tébar et al, 2020; Shajahan et al, 2019). Humidity, nutrients, and temperature are the most important factors that influence the growth of airborne fungi (Haleem Khan & Mohan Karuppayil, 2012).…”

“…Although the influence of the position of the HEPA filter on the presence of fungi in the air has been demonstrated, other factors also influence the level of containment of the rooms (ACH and differential pressure). These parameters contribute to the maintenance of environmental biosafety by preventing the entry of microorganisms from adjacent spaces, by renewing the air, and by maintaining the cleanliness of the air and surfaces (Sabuco-Tébar et al, 2020; Sehulster et al, 2003). UNE 171340 (2020) establishes 15 ACH for very high risk, high risk, and medium risk rooms (type of the rooms analyzed in this research); 10 ACH for low risk; and five ACH for minimal risk rooms.…”

“…Heating, Ventilation, and Air Conditioning (HVAC) systems can help reduce the presence of microorganisms in the air and on surfaces in hospital rooms through dilution, pressurization, and adequate filtration processes (Belizario et al, 2021; Dai et al, 2021; Li et al, 2007; Lin et al, 2022; Sabuco-Tébar et al, 2020; Stockwell et al, 2019). UNE 100713 (2005) is the Spanish standard of reference for air conditioning in hospitals.…”

Evaluation of the Results of a Periodic Environmental Biosecurity Assessment Program on Air Quality in Controlled Environment Rooms of Hospitals

“…Significant differences were reported in temperature and relative humidity between rooms. Parameters such as temperature and relative humidity influence the growth and survival of microorganisms (Sabuco-Tébar et al, 2020; Sehulster et al, 2003; Wagenvoort et al, 1993). A review concluded that fungi and bacteria had different survival conditions regarding temperature and relative humidity; temperatures above about 24°C (75.2°F) decrease the air survival of gram-negative, gram-positive, and intracellular bacteria, while fungi are more resistant in extreme environmental conditions and survive in higher temperatures (Tang, 2009).…”