Sewer biofilm microbiome and antibiotic resistance genes as function of pipe material, source of microbes, and disinfection: field and laboratory studies

Abstract

<p>Wastewater systems are recognized pathways for the spread of antibiotic resistant bacteria, but relatively little is known about the microbial ecology of the sewer environment.</p>

Metabolically Active Prokaryotes and Actively Transcribed Antibiotic Resistance Genes in Sewer Systems: Implications for Public Health and Microbially Induced Corrosion

“…This has consistently been reported as the most abundant ARG among all matrices in sewer system (wastewater [ 3 – 5 , 7 , 32 ], sewer sediment [ 2 , 5 ], and biofilms [ 2 , 7 ]) including in the paired DNA samples for this study ranging from − 1 to − 2 Log10 copies per copy of 16S rRNA gene [ 5 ]. tet (G) and bla TEM have also been commonly detected in sewer bacterial communities [ 2 – 5 , 7 , 32 , 33 ]. tet (G) ranged between − 2 and − 3.5 Log10 copies per copy of 16S rRNA gene.…”

“…This suggests that abundance of an ARG at the metagenomic level (total DNA) does not necessary correlate with abundance of the actively transcribed gene (mRNA). The low abundance of transcribed ARGs may also suggest that even though genomic studies have highlighted sewer systems as hotspots of ARGs [ 2 , 4 , 5 , 7 , 9 ], the proliferation of ARGs do not scale linearly with the proliferation of antibiotic-resistant bacteria. Therefore, the use of metagenomic approaches to estimate abundance of antibiotic resistance bacteria in sewer systems will most likely result in overestimation of these cells.…”

“…Antibiotic-resistant infections are the cause of more than 35,000 deaths a year and the US Centers for Disease Control (CDC) has classified antibiotic resistance as one of the biggest public heath challenges of our time [ 1 ]. Sewer systems have been shown to be a potential environmental hotspot for the proliferation of bacteria carrying antibiotic resistance genes (ARGs) and potential human pathogens [ 2 – 7 ]. However, most of these studies have been limited to genomic DNA-based analysis that cannot measure gene expression nor discriminate between living cells and DNA from non-living cells (unless further steps are taken such as PMA-PCR or stable isotope probing).…”

Accumulation of SARS-CoV-2 RNA in Sewer Biofilms

“…In fact, another study demonstrated that strains of enteroviruses and noroviruses, which are human pathogenic RNA viruses similar to Poliovirus and SARS-CoV-2, can accumulate in sewer biofilms, 17,18 but no studies, to the authors' knowledge, have evaluated if this is the case with SARS-CoV- microbial ecology of sewer solids include field sampling, 19,20 plug flow reactors, 21 and annular biofilm reactors. 19,22 Annular biofilm reactors can simulate the shear stress that sewer biofilms should experience during self-cleaning design flow: for open channel sewer design, the typical design velocity would be 0.60 m/s, and for force mains, the typical design velocity would be 0.60 m/s−3 m/s. 23 A second benefit of annular biofilm reactors is that different pipe materials can be tested in parallel through the use of reactors with coupon holders.…”

“…Using an annular biofilm reactor, previous research demonstrated that wastewater quality was a more important factor than pipe material for accumulation of antibiotic resistance gene carrying microbes and microbial communities in controlled simulated sewer experiments. 19 Annular reactors allow for controlling other variables, although notably, the impact of temperature is not expected to be great in the study area, the northern US where a minimum cover of ∼3 m for prevention of freezing is usually required, which keeps sewer temperatures to a smaller range. 23 The reactor results can be compared to field observations of SARS-CoV-2 in sewer biofilms, demonstrated near the point of entry during a period of low COVID-19 prevalence in a dormitory monitoring study our team conducted.…”