Understanding the influence of the bioaerosol source on the distribution of airborne bacteria in hospital indoor air

Víctor Pertegal; Engracia Lacasa; Pablo Cañizares; Manuel A Rodrigo; Cristina Sáez

doi:10.1016/j.envres.2022.114458

Understanding the influence of the bioaerosol source on the distribution of airborne bacteria in hospital indoor air

Environ Res. 2023 Jan 1;216(Pt 1):114458. doi: 10.1016/j.envres.2022.114458. Epub 2022 Sep 29.

Authors

Víctor Pertegal¹, Engracia Lacasa², Pablo Cañizares³, Manuel A Rodrigo³, Cristina Sáez⁴

Affiliations

¹ Department of Chemical Engineering, Higher Technical School of Industrial Engineering, University of Castilla-La Mancha, Edificio Infante Don Juan Manuel, Campus Universitario S/n, 02071, Albacete, Spain.
² Department of Chemical Engineering, Higher Technical School of Industrial Engineering, University of Castilla-La Mancha, Edificio Infante Don Juan Manuel, Campus Universitario S/n, 02071, Albacete, Spain. Electronic address: engracia.lacasa@uclm.es.
³ Department of Chemical Engineering, Faculty of Chemical Sciences and Technologies, University of Castilla-La Mancha, Edificio Enrique Costa Novella, Campus Universitario S/n, 13005, Ciudad Real, Spain.
⁴ Department of Chemical Engineering, Faculty of Chemical Sciences and Technologies, University of Castilla-La Mancha, Edificio Enrique Costa Novella, Campus Universitario S/n, 13005, Ciudad Real, Spain. Electronic address: cristina.saez@uclm.es.

PMID: 36181895
DOI: 10.1016/j.envres.2022.114458

Abstract

The composition and concentration of airborne microorganisms in hospital indoor air has been reported to contain airborne bacteria and fungi concentrations ranged 10¹-10³ CFU/m³ in inpatients facilities which mostly exceed recommendations from the World Health Organization (WHO). In this work, a deeper knowledge of the performance of airborne microorganisms would allow improving the designs of the air-conditioning installations to restrict hospital-acquired infections (HAIs). A solution containing Escherichia coli (E. coli) as a model of airborne bacteria was nebulized using the Collison nebulizer to simulate bioaerosols in various hospital areas such as patients' rooms or bathrooms. Results showed that the bioaerosol source had a significant influence on the airborne bacteria concentrations since 4.00 10², 6.84 10³ and 1.39 10⁴ CFU mL^-1 were monitored during the aerosolization for 10 min of urine, saliva and urban wastewater, respectively. These results may be explained considering the quite narrow distribution profile of drop sizes around 1.10-1.29 μm obtained for urban wastewater, with much vaster distribution profiles during the aerosolization of urine or saliva. The airborne bacteria concentration may increase up to 10⁷ CFU mL^-1 for longer sampling times and higher aerosolization pressures, causing several cell damages. The cell membrane damage index (I_D) can vary from 0 to 1, depending on the genomic DNA releases from bacteria. In fact, the I_D of E. coli was more than two times higher (0.33 vs. 0.72) when increasing the pressure of air flow was applied from 1 to 2 bar. Finally, the ventilation air flow also affected the distribution of bioaerosols due to its direct relationship with the relative humidity of indoor air. Specifically, the airborne bacteria concentration diminished almost below 3-logs by applying more than 10 L min^-1 during the aerosolization of urine due to their inactivation by an increase in their osmotic pressure.

Keywords: Bioaerosol; Hospital; Saliva; Urban wastewater; Urine.

Publication types

Research Support, Non-U.S. Gov't

MeSH terms

Aerosols / analysis
Air Microbiology*
Air Pollution, Indoor* / analysis
Bacteria / genetics
Environmental Monitoring
Escherichia coli
Fungi
Hospitals
Humans
Wastewater

Substances

Waste Water
Aerosols