Papers by William R Morales Medina
Wastewater-based epidemiology is a useful tool to exist for normalizing wastewater virus concentr... more Wastewater-based epidemiology is a useful tool to exist for normalizing wastewater virus concentrations to the flow and number of people in the sewershed, less information is available regarding the potential for in-sewer processes to impact these observations. The aim of this research was to evaluate SARSCoV-2 accumulation in simulated sewer biofilms. An annular biofilm reactor was continuously fed with raw wastewater from a separate sanitary sewer during periods of high and low COVID-19 incidence. Periodic biofilm samples were collected, and SARSCoV-2 and pepper mottle virus gene copies were quantified via RT-qPCR. During the period of low COVID-19 incidence, SARSCoV-2 was below detection or below the quantitation limit in the sewer biofilms. During the period of high COVID-19 incidence, SARS-CoV-2 gene copies increased in the sewer biofilm across the 4-week study period. Accumulation of similar to 700 genome copies/cm(2) was observed in the biofilm and correlated with cumulative cases in the county. During both study periods, the pepper mottle virus plateaued after 1 week. These results provide insight into the potential for SARS-CoV-2 retardation in sewer biofilms, which may be of interest for interpreting wastewater-based epidemiology data, protecting utility workers, and monitoring infections.
Water Environment Research
Microbial Ecology, 2021
Sewer systems are reservoirs of pathogens and bacteria carrying antibiotic resistance genes (ARGs... more Sewer systems are reservoirs of pathogens and bacteria carrying antibiotic resistance genes (ARGs). However, most recent high-throughput studies rely on DNA-based techniques that cannot provide information on the physiological state of the cells nor expression of ARGs. In this study, wastewater and sewer sediment samples were collected from combined and separate sanitary sewer systems. The metabolically active prokaryote community was evaluated using 16S rRNA amplicon sequencing and actively transcribed ARG abundance was measured using mRNA RT-qPCR. Three (sul1, bla TEM , tet(G)) of the eight tested ARGs were quantifiable in select samples. Sewer sediment samples had greater abundance of actively transcribed ARGs compared to wastewater. Microbiome analysis showed the presence of metabolically active family taxa that contain clinically relevant pathogens (Pseudomonadaceae, Enterobacteraceae, Streptococcaceae, Arcobacteraceae, and Clostridiaceae) and corrosion-causing prokaryotes (Desulfobulbaceae and Desulfovibrionaceae) in both matrices. Spirochaetaceae and methanogens were more common in the sediment matrix while Mycobacteraceae were more common in wastewater. The microbiome obtained from 16S rRNA sequencing had a significantly different structure from the 16S rRNA gene microbiome. Overall, this study demonstrates active transcription of ARGs in sewer systems and provides insight into the abundance and physiological state of taxa of interest in the different sewer matrices and sewer types relevant for wastewater-based epidemiology, corrosion, and understanding the hazard posed by different matrices during sewer overflows.
Science of The Total Environment, 2021
Wastewater surveillance has been used as tool for outbreak detection for COVID-19 particularly wh... more Wastewater surveillance has been used as tool for outbreak detection for COVID-19 particularly where there was not capability in place for routine and robust individual testing. Given clinical reports that earlier detection is possible following infection from throat/nasal samples compared to fecal samples for COVID-19 patients, the utility of wastewater testing where robust individual testing is possible is less clear. The objective of this study was to compare the results of weekly required COVID-19 saliva tests to weekly wastewater monitoring for residential buildings (i.e., dormitories) located across three college campuses capturing wastewater from 80 to 441 occupants per sampling location. Sampling occurred during the spring semester of the 2021 academic year which captured the third wave of SARS-CoV-2 cases in the study region. Comparison of the saliva and wastewater testing results indicated that the wastewater SARS-CoV-2 concentrations had a strong linear correlation with the previous week's percentage of positive saliva test results and a weak linear correlation with the saliva testing results surrounding the wastewater sampling (four days before and 3 days after). Given that no correlation was observed between the wastewater and the saliva testing from the following week, the weekly saliva testing captured spikes in COVID-19 cases earlier than the weekly wastewater sampling. Interestingly, the N1 gene copy was observed in buildings on all campuses, but N2 was observed in wastewater on only one of the campuses. N1 and N2 were also observed in sewer biofilm. The campus-specific challenges associated with implementation of wastewater surveillance are discussed. Overall, these results can help inform design of surveillance for early detection of SARS-CoV-2 in residential settings informing mitigation strategies to slow or prevent the spread of the virus among residents in congregate living.
Environmental Science: Water Research & Technology, 2019
Fecal indicator bacteria are commonly used to evaluate water quality and make decisions on design... more Fecal indicator bacteria are commonly used to evaluate water quality and make decisions on designating and restricting use. A drawback of this method is that it does not differentiate fecal...
Science of The Total Environment, 2018
Antibiotic resistance is a public health issue with links to environmental sources of antibiotic ... more Antibiotic resistance is a public health issue with links to environmental sources of antibiotic resistance genes (ARGs). ARGs from nonviable sources may pose a hazard given the potential for transformation whereas ARGs in viable sources may proliferate during host growth or conjugation. In this study, ARGs in the effluent from three municipal wastewater treatment plants (WWTPs) and the receiving surface waters were investigated using a viability-based qPCR technique (vPCR) with propidium monoazide (PMA). ARGs sul1, tet(G), and bla TEM , fecal indicator marker BacHum, and 16S rRNA gene copies/mL were found to be significantly lower in viable-cells than in total concentrations for WWTP effluent. Viable-cell and total gene copy concentrations were similar in downstream samples except for tet(G). Differences with respect to season in the prevalence of nonviable ARGs in surface water or WWTP effluent were not observed. The results of this study indicate that qPCR may overestimate viable-cell ARGs and fecal indicator genes in WWTP effluent but not necessarily in the surface water >1.8km downstream.
Environmental Science: Water Research & Technology, 2017
Combined sewer overflows (CSOs) degrade water quality and end-of-pipe treatment is one potential ... more Combined sewer overflows (CSOs) degrade water quality and end-of-pipe treatment is one potential solution for retrofitting this outdated infrastructure.
Environmental science : water research & technology, 2020
Wastewater systems are recognized pathways for the spread of antibiotic resistant bacteria, but r... more 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. Sewer biofilm colonization by antibiotic resistance gene (ARG) carrying bacteria may impact interpretations of sewage epidemiology data, water quality during sewer overflows, and hazard to utility workers. The objectives of this research were to evaluate the (1) microbiome of real and simulated sewer biofilms and their potential to accumulate ARGs and (2) susceptibility of simulated sewer biofilms to bleach disinfection. First, biofilm samples were collected from sewer municipal systems. Next, an annular biofilm reactor was used to simulate the sewer environment while controlling the pipe material (concrete vs. PVC). The reactor was operated either as fed semi-batch with sewer sediment and synthetic wastewater (Sed-SB) or fed with a continuous flow of raw sewage (WW-CF). The abundance of ARGs, human fecal mar...
Environmental Science: Water Research & Technology
The sewer environment is a potential hotspot for the proliferation of antibiotic resistance genes... more The sewer environment is a potential hotspot for the proliferation of antibiotic resistance genes (ARGs) and other hazardous microbial agents.
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Papers by William R Morales Medina