Extended water stagnation in buildings during the COVID-19 pandemic increases the risks posed by opportunistic pathogens

Casey K Huang; Anjani Weerasekara; Ji Lu; Robyn Carter; Karen D Weynberg; Rachel Thomson; Scott Bell; Jianhua Guo

doi:10.1016/j.wroa.2023.100201

Extended water stagnation in buildings during the COVID-19 pandemic increases the risks posed by opportunistic pathogens

Water Res X. 2023 Sep 9:21:100201. doi: 10.1016/j.wroa.2023.100201. eCollection 2023 Dec 1.

Authors

Casey K Huang^{1

2}, Anjani Weerasekara^{1

2}, Ji Lu¹, Robyn Carter³, Karen D Weynberg⁴, Rachel Thomson^{3

5}, Scott Bell^{6

7

8}, Jianhua Guo¹

Affiliations

¹ Australian Centre for Water and Environmental Biotechnology (ACWEB, formerly AWMC), The University of Queensland, QLD 4072, Australia.
² Queensland Alliance for Environmental Health Sciences (QAEHS), The University of Queensland, QLD 4102, Australia.
³ Respiratory Research Unit, Gallipoli Medical Research Institute, QLD 4120, Australia.
⁴ Australian Centre for Ecogenomics, School of Chemistry and Molecular Biosciences, The University of Queensland, St Lucia, Brisbane, QLD 4072, Australia.
⁵ Greenslopes Clinical Unit, The University of Queensland, QLD Australia.
⁶ Adult Cystic Fibrosis Centre, The Prince Charles Hospital, Australia.
⁷ Child Health Research Centre, Faculty of Medicine, The University of Queensland, QLD Australia.
⁸ Translational Research Institute, Australia.

Abstract

The regrowth and subsequent exposure of opportunistic pathogens (OPs) whilst reopening buildings that have been locked down due to the stay-at-home restrictions to limit the spread of COVID-19, is a public health concern. To better understand such microbiological risks due to lowered occupancy and water demand in buildings, first and post-flush water samples (n = 48) were sampled from 24 drinking water outlets from eight university buildings in two campuses (urban and rural), with various end-user occupancies. Both campuses were served with chlorinated water originating from a single drinking water distribution system in South-East Queensland, situated 14 km apart, where the rural campus had lower chlorine residuals. Culture-dependent and culture-independent methods (such as flow cytometry, qPCR and 16S rRNA gene amplicon sequencing) were used concurrently to comprehensively characterise the OPs of interest (Legionella spp., Pseudomonas aeruginosa, and nontuberculous mycobacteria (NTM)) and the premise plumbing microbiome. Results showed that buildings with extended levels of stagnation had higher and diverse levels of microbial growth, as observed in taxonomic structure and composition of the microbial communities. NTM were ubiquitous in all the outlets sampled, regardless of campus or end-user occupancy of the buildings. qPCR and culture demonstrated prevalent and higher concentrations of NTM in buildings (averaging 3.25 log₁₀[estimated genomic copies/mL]) with extended stagnation in the urban campus. Furthermore, flushing the outlets for 30 minutes restored residual and total chlorine, and subsequently decreased the levels of Legionella by a reduction of 1 log. However, this approach was insufficient to restore total and residual chlorine levels for the outlets in the rural campus, where both Legionella and NTM levels detected by qPCR remained unchanged, regardless of building occupancy. Our findings highlight that regular monitoring of operational parameters such as residual chlorine levels, and the implementation of water risk management plans are important for non-healthcare public buildings, as the levels of OPs in these environments are typically not assessed.

Keywords: Building microbiome; COVID-19 pandemic; Legionella; Nontuberculous mycobacteria (NTM); Opportunistic pathogens; Premise plumbing.