Summary
Background
Identifying the extent of environmental contamination of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is essential for infection control and prevention. The extent of environmental contamination has not been fully investigated in the context of severe coronavirus disease (COVID-19) patients.
Aim
To investigate environmental SARS-CoV-2 contamination in the isolation rooms of severe COVID-19 patients requiring mechanical ventilation or high-flow oxygen therapy.
Methods
We collected environmental swab samples and air samples from the isolation rooms of three COVID-19 patients with severe pneumonia. Patient 1 and Patient 2 received mechanical ventilation with a closed suction system, while Patient 3 received high-flow oxygen therapy and noninvasive ventilation. Real-time reverse transcription polymerase chain reaction (rRT-PCR) was used to detect SARS-CoV-2; viral cultures were performed for samples not negative on rRT-PCR.
Findings
Of the 48 swab samples collected in the rooms of Patient 1 and Patient 2, only samples from the outside surfaces of the endotracheal tubes tested positive for SARS-CoV-2 by rRT-PCR. However, in Patient 3’s room, 13 of the 28 environmental samples (fomites, fixed structures, and ventilation exit on the ceiling) showed positive results. Air samples were negative for SARS-CoV-2. Viable viruses were identified on the surface of the endotracheal tube of Patient 1 and seven sites in Patient 3’s room.
Conclusion
Environmental contamination of SARS-CoV-2 can be a route of viral transmission. However, it might be minimized when patients receive mechanical ventilation with a closed suction system. These findings can provide evidence for guidelines for the safe use of personal protective equipment.
Point-of-care risk assessment (PCRA) for airborne viruses requires a system that can enrich low-concentration airborne viruses dispersed in field environments into a small volume of liquid. In this study, airborne virus particles were collected to a degree above the limit of detection (LOD) for a real-time quantitative reverse transcription polymerase chain reaction (qRT-PCR). This study employed an electrostatic air sampler to capture aerosolized test viruses (human coronavirus 229E (HCoV-229E), influenza A virus subtype H1N1 (A/H1N1), and influenza A virus subtype H3N2 (A/H3N2)) in a continuously flowing liquid (aerosol-to-hydrosol (ATH) enrichment) and a concanavalin A (ConA)-coated magnetic particles (CMPs)-installed fluidic channel for simultaneous hydrosol-to-hydrosol (HTH) enrichment. The air sampler's ATH enrichment capacity (EC) was evaluated using the aerosol counting method. In contrast, the HTH EC for the ATH-collected sample was evaluated using transmission-electron-microscopy (TEM)-based image analysis and real-time qRT-PCR assay. For example, the ATH EC for HCoV-229E was up to 67,000, resulting in a viral concentration of 0.08 PFU/mL (in a liquid sample) for a viral epidemic scenario of 1.2 PFU/m
3
(in air). The real-time qRT-PCR assay result for this liquid sample was “non-detectable” however, subsequent HTH enrichment for 10 min caused the “non-detectable” sample to become “detectable” (cycle threshold (CT) value of 33.8 ± 0.06).
Rapid monitoring of biological particulate
matter (Bio-PM, bioaerosols)
requires an enrichment technique for concentrating the Bio-PM dispersed
in the air into a small volume of liquid. In this study, an electrostatic
air sampler is employed to capture aerosolized test bacteria in a
carrier liquid (aerosol-to-hydrosol (ATH) enrichment). Simultaneously,
the captured bacteria are carried into a fluid channel for hydrosol-to-hydrosol
(HTH) enrichment with Concanavalin A coated magnetic particles (CMPs).
The ATH enrichment capacity of the air sampler was evaluated with
an aerosol particle counter for the following test bacteria: Staphylococcus aureus, Bacillus cereus, Escherichia coli, and Acinetobacter baumannii. Then, the HTH enrichment
capacity for the ATH-collected sample was evaluated using the colony-counting
method, scanning electron microscopy based image analysis, fluorescence
microscopy, electrical current measurements, and real-time quantitative
polymerase chain reaction (qPCR). The ATH and HTH enrichment capacities
for the given operation conditions were up to 80 000 and 14.9,
respectively, resulting in a total enrichment capacity of up to 1.192
× 106. Given that air-to-liquid enrichment required
to prepare detectable bacterial samples for real-time qPCR in field
environments is of the order of at least 106, our method
can be used to prepare a detectable sample from low-concentration
airborne bacteria in the field and significantly reduce the time required
for Bio-PM monitoring because of its enrichment capacity.
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