Sewer slime can hang on to SARS-CoV-2 RNA from wastewater

Date:
February 9, 2022
Source:
American Chemical Society
Summary:
Researchers report that sewer slime can accumulate SARS-CoV-2 RNA,
which could decompose or slough off later, potentially impacting
the accuracy of wastewater epidemiology studies.



FULL STORY ========================================================================== During the COVID-19 pandemic, monitoring the levels of SARS-CoV-2
RNA in wastewater entering treatment plants has been one way that
researchers have gauged the disease's spread. But could the slimy
microbial communities that line most sewer pipes affect the viral RNA
they encounter? In a first-of-its- kind study, researchers report in ACS
ES&T Water that sewer slime can accumulate SARS-CoV-2 RNA, which could decompose or slough off later, potentially impacting the accuracy of
wastewater epidemiology studies.


==========================================================================
As the water and sludge from people's homes converge in sewers, some
of the solids settle out, and gooey microbial biofilms build up within
the pipes.

Previous researchers have shown that RNA viruses, such as poliovirus, enteroviruses and noroviruses, can get trapped and collect in this
slime. Yet whether the sticky material can also accumulate SARS-CoV-2
viral particles or RNA from wastewater is unknown. Nicole Fahrenfeld and colleagues previously detected the virus's RNA in sewer deposits from a university dormitory with a low number of COVID-19 cases, but the amount
was too low to accurately assess.

So, the team wanted to see if biofilms could incorporate SARS-CoV-2 RNA
from untreated wastewater during times of low and high COVID-19 incidence.

To grow a simulated sewer slime, the researchers continuously pumped raw wastewater into a cylindrical tank with removable pieces of polyvinyl
chloride (PVC) inside. They conducted two 28-day experiments, removing
PVC plates every few days to assess the biofilm's composition. Then
the team used the method called reverse transcription quantitative
polymerase chain reaction to measure the abundance of SARS-CoV-2 RNA and
pepper mottle virus (an indicator of human feces) RNA in the untreated wastewater and the biofilms.

In August and September 2020, the levels of SARS-CoV-2 RNA were too low to accurately measure in both the simulated sewer slime and the wastewater
from which it grew. These results align with a low incidence of COVID-19 infections at that time, the researchers say. Then, during November
and December 2020, although SARS-CoV-2's presence in the wastewater
itself was still low, its RNA levels increased in the slime. The amount
of pepper mottle virus RNA plateaued within the first week of growth, indicating that the rise of SARS-CoV-2 RNA in the biofilm wasn't because
of a boost in fecal volume. Rather, this change reflected the higher
number of diagnosed COVID-19 cases in late fall. It's still too early to
know exactly how these biofilms impact wastewater epidemiology studies,
since other factors need to be assessed first, say the researchers. For example, the RNA could get broken down, or it could be released into
wastewater later on when the biofilms break apart.

The authors acknowledge funding from the U.S. National Science Foundation,
the Rutgers Center for COVID-19 Response and Pandemic Preparedness and a Rutgers School of Graduate Studies Acceleration and Completion Fellowship.

========================================================================== Story Source: Materials provided by American_Chemical_Society. Note:
Content may be edited for style and length.


========================================================================== Journal Reference:
1. William R. Morales Medina, Stephanie D'Elia, Nicole L. Fahrenfeld.

Accumulation of SARS-CoV-2 RNA in Sewer Biofilms. ACS ES&T Water,
2022; DOI: 10.1021/acsestwater.1c00345 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2022/02/220209093450.htm

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