Reaerosolization of Spores from Flooring Surfaces To Assess the Risk of Dissemination and Transmission of Infections

Susan Paton, Katy-Anne Thompson, Simon R. Parks, Allan M. Bennett

The aim of this study was to quantify reaerosolization of microorganisms caused by walking on contaminated flooring to assess the risk to individuals accessing areas contaminated with pathogenic organisms, for example, spores of Bacillus anthracis. In- dustrial carpet and polyvinyl chloride (PVC) floor coverings were contaminated with aerosolized spores of Bacillus atrophaeus by using an artist airbrush to produce deposition of 10(3rd) to 10(4th) CFU · cm-(squared). Microbiological air samplers were used to quantify the particle size distribution of the aerosol generated when a person walked over the floorings in an environmental chamber. Results were expressed as reaerosolization factors (percent per square centimeter per liter), to represent the ratio of air concen- tration to surface concentration generated. Walking on carpet generated a statistically significantly higher reaerosolization fac- tor value than did walking on PVC (t = 12.421; P < 0.001). Height also had a statistically significant effect on the reaerosolization factor, with higher rates of recovery of B. atrophaeus at lower levels, demonstrating a height-dependent gradi- ent of particle reaerosolization. Particles in the respirable size range were recovered in all sampling scenarios (mass mean diame- ters ranged from 2.6 to 4.1 um).The results of this study can be used to produce a risk assessment of the potential aerosol expo- sure of a person accessing areas with contaminated flooring in order to inform the choice of appropriate respiratory protective equipment and may aid in the selection of the most suitable flooring types for use in health care environments, to reduce aerosol transmission in the event of contamination.