Continuous monitoring of aerial bioburden within intensive care isolation rooms and identification of 'high risk' activities

Background: The spread of pathogens via the airborne route is often underestimated and little is known about the extent to which airborne microbial contamination levels vary throughout the day and night in hospital facilities. Aims: This study aims to evaluate variability in airborne contamination levels within ICU isolation rooms over extended time periods to improve understanding of the extent to which ward activities, and consequential increases in airborne bioburden, may contribute to cross-infection of patients. Methods: Environmental air monitoring was conducted within occupied and vacant inpatient isolation rooms. A sieve impactor sampler was used to collect 500 L air samples every 15 minutes over 10-hour (08:00-18:00 h) and 24-hour (08:00-08:00 h) periods. Samples were collected, room activity logged, and the bacterial contamination levels were recorded as cfu/m3 of air. Findings: A high degree of variability in levels of airborne contamination was observed across all scenarios in the studied isolation rooms. Air bioburden increased as room occupancy increased, with air contamination levels highest in rooms occupied for the longest time during the study (10 days) with a mean value of 104.4 cfu/m3 and a range of 12–510 cfu/m3. Counts were lowest in unoccupied rooms, with an average value of 20 cfu/m3 and during the night. Conclusion: Peaks in airborne contamination showed a direct relation to an increase in activity levels. This study provides first clear evidence of the extent of variability in microbial airborne levels over 24-hour periods in ICU isolation rooms and directly correlates microbial load to ward activity.