I ncreased demand on water supplies, associated with population growth and changes in climatic pa... more I ncreased demand on water supplies, associated with population growth and changes in climatic patterns, has made it necessary for many utilities to consider augmenting their current drinking water sources with recycled water-i.e., potable reuse. For regions with imminent water supply shortages due to uncharacteristically long periods of drought or significant population shifts, the primary options for increasing water supply are water importation, saltwater desalination, and water reuse (Snyder 2014). Water reuse may include a combination of potable and nonpotable uses to increase water supply resiliency. Nonpotable reuse is water not intended for direct human consumption, such as irrigation or coolingtower water. Potable reuse involves integrating highly treated municipal wastewater directly into drinking water systems, which may or may not include retention in an engineered storage buffer before its introduction, such as direct versus indirect potable reuse. CURRENT EXTENT OF POTABLE REUSE In the United States, approximately 7-8% of the 32 bil gal of treated municipal wastewater effluent is recycled (USEPA 2012).
The use of nontraditional water sources, including reclaimed or recycled water, has become a desi... more The use of nontraditional water sources, including reclaimed or recycled water, has become a desirable option to meet increasing demands in water stressed regions. In the Southwest United States, utilization of alternative water sources is becoming increasingly common, including use for landscape irrigation, environmental enhancement, cooling and power generation, potable reuse, and as a source water for agricultural irrigation. While much research has gone into identifying public perception towards water reuse schemes, little attention has been given to understanding grower attitudes, perceptions, and knowledge on the use of nontraditional water, including reclaimed water, in agriculture and how that may influence grower acceptance and production practices. This unique study utilized a needs assessment survey of growers (n=521) within the Southwest region of the United States to gain an understanding of industry attitudes and needs regarding nontraditional water in agriculture. Results indicate that the majority of survey respondents were concerned with water availability (67.49%) yet less than half (48.30%) thought using a nontraditional water source in agriculture was 'very important'. Interestingly, respondents rated irrigation of 'food crops' third (42.20%) among agricultural activities for which they would be willing to use nontraditional water sources, behind irrigation of forage crops (61.60%) and dust control (61.60%). The importance of the use of nontraditional water sources in agriculture was influenced mostly by farm size (p=0.007) and primary water source (p=0.016), and the level of education was significant in respondent's level of concern over water availability (p=0.021). Information on the quality of nontraditional water sources, showing that it is as good or better than respondents current sources, was found to shift rejection and uncertainty towards acceptance by 16.04%. The results of this study provide insight into perceived risks, willingness to use, drivers and constraints to grower adoption, and preferred
The increasing use of treated wastewater for irrigation heightens the importance of accurate moni... more The increasing use of treated wastewater for irrigation heightens the importance of accurate monitoring of water quality. Chromogenic media, because they are easy to use and provide rapid results, are often used for detection of Escherichia coli in environmental samples, but unique levels of organic and inorganic compounds alter the chemistry of treated wastewater, potentially hindering the accurate performance of chromogenic media. We used MI agar and molecular confirmatory methods to assess false-positive identification of E. coli in treated wastewater samples collected from municipal utilities, an irrigation holding pond, irrigated soils, and in samples collected from storm flows destined for groundwater recharge. False-positive rates in storm flows (4.0%) agreed closely with USEPA technical literature but were higher in samples from the pond, soils, and treatment facilities (33.3%, 38.0%, and 48.8%, respectively). Sequencing of false-positive isolates confirmed that most were, l...
The California State Water Resources Control Board is the first regulatory body in the United Sta... more The California State Water Resources Control Board is the first regulatory body in the United States to develop statewide regulations for direct potable reuse (DPR). To support this effort, a pathogen monitoring campaign was undertaken to develop and implement an optimized standard operating protocol to better characterize the concentration of human pathogens in raw wastewater. Methods to detect relevant viral and protozoan pathogens in raw wastewater were optimized and implemented during a 14-month monitoring campaign. Over 120 samples were collected from five wastewater treatment plants treating a quarter of California's population. Samples were analyzed for two protozoa (Cryptosporidium and Giardia) using microscopy methods, three enteric viruses (enterovirus, adenovirus, and norovirus) using culture and/or molecular methods, and male-specific coliphage using culture methods. The method recovery efficiency was measured in every protozoa sample and every other virus sample to confirm minimum recovery efficiencies were achieved and to correct the concentrations for pathogen losses during sample processing. The results from this study provide the industry with a large, high-quality dataset as demonstrated by the high degree of method sensitivity, method recovery, and QA/QC steps. Such high-quality data on pathogen concentrations in raw wastewater are critical for confirming the level of treatment needed to reduce pathogen concentrations down to acceptable levels for potable water in DPR projects.
Pathogen contamination of agricultural water has been identified as a probable cause of recalls a... more Pathogen contamination of agricultural water has been identified as a probable cause of recalls and outbreaks. However, variability in pathogen presence and concentration complicates the reliable identification of agricultural water at elevated risk of pathogen presence. In this study, we collected data on the presence of Salmonella and genetic markers for enterohemorrhagic E. coli (EHEC; PCR-based detection of stx and eaeA) in southwestern US canal water, which is used as agricultural water for produce. We developed and assessed the accuracy of models to predict the likelihood of pathogen contamination of southwestern US canal water. Based on 169 samples from 60 surface water canals (each sampled 1–3 times), 36% (60/169) and 21% (36/169) of samples were positive for Salmonella presence and EHEC markers, respectively. Water quality parameters (e.g., generic E. coli level, turbidity), surrounding land-use (e.g., natural cover, cropland cover), weather conditions (e.g., temperature), ...
We have all heard the saying “food grows where water flows,” but in the Western United States, ag... more We have all heard the saying “food grows where water flows,” but in the Western United States, agriculture’s share of freshwater supplies have been under pressure. This has been especially true in parts of Arizona, where the majority of the state was classified as suffering moderate to severe drought conditions in June 2014 (ADWR, 2014a). Lack of precipitation, combined with widespread urbanization of farmland has stimulated the transfer of water rights away from agriculture. But in turn, urbanization has also accelerated an increase in a completely new source of irrigation water: recycled municipal wastewater, defined by the Arizona Legislature as “water that has been treated or processed by a wastewater treatment plant or an on-site wastewater treatment facility” (AZLEG, 2014).
Pre harvest irrigation water represents a key potential source of pathogenic bacteria during the ... more Pre harvest irrigation water represents a key potential source of pathogenic bacteria during the production of fresh produce. Industry guidance metrics uniformly identify generic Escherichia coli (E. coli) as a practical and cost‐effective indicator of fecal contamination in water. Although generic E. coli satisfies most characteristics of an ideal bacterial indicator, very limited correlation exists between the presence of E. coli, pathogen presence, and microbial risk to consumers following consumption. The Food Safety Modernization Act’s Produce Safety Rule’s Microbial Water Quality Profile is under abeyance due to concerns that there is not enough scientific evidence to support the rule in its’ current form; thus, it is important to examine feasible alternative indicator organisms which could improve agricultural water quality assessment and the protection of public health. This work examines the bacterial group, Bacteroides for prediction of pathogens in irrigation water sample...
Environmental Science: Water Research & Technology, 2020
Brian Pecson and Daniel Gerrity present an Editorial Perspective which focuses on the impact of S... more Brian Pecson and Daniel Gerrity present an Editorial Perspective which focuses on the impact of SARS-CoV-2 on the water industry.
Agricultural water is an important source of foodborne pathogens on produce farms. Managing water... more Agricultural water is an important source of foodborne pathogens on produce farms. Managing water-associated risks does not lend itself to one-size-fits-all approaches due to the heterogeneous nature of freshwater environments. To improve our ability to develop location-specific risk management practices, a study was conducted in two produce-growing regions to (i) characterize the relationship between Escherichia coli levels and pathogen presence in agricultural water, and (ii) identify environmental factors associated with pathogen detection. Three AZ and six NY waterways were sampled longitudinally using 10-L grab samples (GS) and 24-h Moore swabs (MS). Regression showed that the likelihood of Salmonella detection (Odds Ratio [OR] = 2.18), and eaeA-stx codetection (OR = 6.49) was significantly greater for MS compared to GS, while the likelihood of detecting L. monocytogenes was not. Regression also showed that eaeA-stx codetection in AZ (OR = 50.2) and NY (OR = 18.4), and Salmonella detection in AZ (OR = 4.4) were significantly associated with E. coli levels, while Salmonella detection in NY was not. Random forest analysis indicated that interactions between environmental factors (e.g., rainfall, temperature, turbidity) (i) were associated with likelihood of pathogen detection and (ii) mediated the relationship between E. coli levels and likelihood of pathogen detection. Our findings suggest that (i) environmental heterogeneity, including interactions between factors, affects microbial water quality, and (ii) E. coli levels alone may not be a suitable indicator of food safety risks. Instead, targeted methods that utilize environmental and microbial data (e.g., models that use turbidity and E. coli levels to predict when there is a high or low risk of surface water being contaminated by pathogens) are needed to assess and mitigate the food safety risks associated with preharvest water use. By identifying environmental factors associated with an increased likelihood of detecting pathogens in agricultural
Current Opinion in Environmental Science & Health, 2020
Abstract Despite the global push for a circular water and nutrient economy, the United States sti... more Abstract Despite the global push for a circular water and nutrient economy, the United States still lags in recycling and reusing valuable waste streams. The reuse of waste streams could result in more sustainable agricultural practices by reducing water withdrawals in stressed environments and nutrient inputs to eutrophication-impacted ecosystems. However, microbial risks are a key barrier to reuse. We identify research and regulatory gaps through a systematic review of quantitative microbial risk assessments (QMRAs) and regulations for biosolids, manure, and human source-separated urine. We propose a cohesive path forward to improve upon existing QMRA approaches, to combine QMRA with other risk frameworks, and to develop integrated monitoring and control strategies by incorporating molecular biology tools. The application of a farm-to-fork risk-based approach that considers the combined use of waste streams is needed to develop comprehensive best management practices, treatment recommendations, and microbial quality criteria that promote food safety while advancing agricultural sustainability.
Сборник содержит статьи Всероссийской научно-практической конференции «Архивы в истории. История ... more Сборник содержит статьи Всероссийской научно-практической конференции «Архивы в истории. История в архивах», посвященной 100-летию Государственной архивной службы России, 95-летию архивной службы Республики Бурятия и 140-летию В.П. Гирченко, историка, архивиста, организатора архивного дела в Бурятии (7 июня 2018 г., г. Улан-Удэ). Тематика статей охватывает исследования по истории становления архивного дела в России, социальной роли архивов и значения архивных документов в сохранении исторической памяти. Адресовано широкому кругу читателей, интересующихся историей и современной жизнью региона.
Treatment of wastewater for potable reuse requires the reduction of enteric viruses to levels tha... more Treatment of wastewater for potable reuse requires the reduction of enteric viruses to levels that pose no significant risk to human health. Advanced water treatment trains (e.g., chemical clarification, reverse osmosis, ultrafiltration, advanced oxidation) have been developed to provide reductions of viruses to differing levels of regulatory control depending upon the levels of human exposure and associated health risks. Importance in any assessment is information on the concentration and types of viruses in the untreated wastewater, as well as the degree of removal by each treatment process. However, it is critical that the uncertainty associated with virus concentration and removal or inactivation by wastewater treatment be understood to improve these estimates and identifying research needs. We reviewed the critically literature to assess to identify uncertainty in these estimates. Biological diversity within families and genera of viruses (e.g. enteroviruses, rotaviruses, adeno...
Bacteria can grow in the presence of trimethoprim and sulfamethoxazole by expressing antibiotic r... more Bacteria can grow in the presence of trimethoprim and sulfamethoxazole by expressing antibiotic resistance genes or by acquiring thymine or thymidine from environmental reservoirs to facilitate DNA synthesis. The purpose of this study was to evaluate whether activated sludge serves as a reservoir for thymine or thymidine, potentially impacting the quantification of antibiotic resistant bacteria. This study also assessed the impacts of varying solids retention time (SRT) on trimethoprim and sulfamethoxazole removal during wastewater treatment and single and multi-drug resistance. When assayed in the presence of the antibiotics at standard clinical concentrations, up to 40% increases in the relative prevalence of resistant bacteria were observed with (1) samples manually augmented with reagent-grade thymidine, (2) samples manually augmented with sonicated biomass (i.e., cell lysate), (3) samples manually augmented with activated sludge filtrate, and (4) activated sludge samples collected from reactors with longer SRTs. These observations suggest that longer SRTs may select for antibiotic resistant bacteria and/or result in false positives for antibiotic resistance due to higher concentrations of free thymine, thymidine, or other extracellular constituents.
I ncreased demand on water supplies, associated with population growth and changes in climatic pa... more I ncreased demand on water supplies, associated with population growth and changes in climatic patterns, has made it necessary for many utilities to consider augmenting their current drinking water sources with recycled water-i.e., potable reuse. For regions with imminent water supply shortages due to uncharacteristically long periods of drought or significant population shifts, the primary options for increasing water supply are water importation, saltwater desalination, and water reuse (Snyder 2014). Water reuse may include a combination of potable and nonpotable uses to increase water supply resiliency. Nonpotable reuse is water not intended for direct human consumption, such as irrigation or coolingtower water. Potable reuse involves integrating highly treated municipal wastewater directly into drinking water systems, which may or may not include retention in an engineered storage buffer before its introduction, such as direct versus indirect potable reuse. CURRENT EXTENT OF POTABLE REUSE In the United States, approximately 7-8% of the 32 bil gal of treated municipal wastewater effluent is recycled (USEPA 2012).
The use of nontraditional water sources, including reclaimed or recycled water, has become a desi... more The use of nontraditional water sources, including reclaimed or recycled water, has become a desirable option to meet increasing demands in water stressed regions. In the Southwest United States, utilization of alternative water sources is becoming increasingly common, including use for landscape irrigation, environmental enhancement, cooling and power generation, potable reuse, and as a source water for agricultural irrigation. While much research has gone into identifying public perception towards water reuse schemes, little attention has been given to understanding grower attitudes, perceptions, and knowledge on the use of nontraditional water, including reclaimed water, in agriculture and how that may influence grower acceptance and production practices. This unique study utilized a needs assessment survey of growers (n=521) within the Southwest region of the United States to gain an understanding of industry attitudes and needs regarding nontraditional water in agriculture. Results indicate that the majority of survey respondents were concerned with water availability (67.49%) yet less than half (48.30%) thought using a nontraditional water source in agriculture was 'very important'. Interestingly, respondents rated irrigation of 'food crops' third (42.20%) among agricultural activities for which they would be willing to use nontraditional water sources, behind irrigation of forage crops (61.60%) and dust control (61.60%). The importance of the use of nontraditional water sources in agriculture was influenced mostly by farm size (p=0.007) and primary water source (p=0.016), and the level of education was significant in respondent's level of concern over water availability (p=0.021). Information on the quality of nontraditional water sources, showing that it is as good or better than respondents current sources, was found to shift rejection and uncertainty towards acceptance by 16.04%. The results of this study provide insight into perceived risks, willingness to use, drivers and constraints to grower adoption, and preferred
The increasing use of treated wastewater for irrigation heightens the importance of accurate moni... more The increasing use of treated wastewater for irrigation heightens the importance of accurate monitoring of water quality. Chromogenic media, because they are easy to use and provide rapid results, are often used for detection of Escherichia coli in environmental samples, but unique levels of organic and inorganic compounds alter the chemistry of treated wastewater, potentially hindering the accurate performance of chromogenic media. We used MI agar and molecular confirmatory methods to assess false-positive identification of E. coli in treated wastewater samples collected from municipal utilities, an irrigation holding pond, irrigated soils, and in samples collected from storm flows destined for groundwater recharge. False-positive rates in storm flows (4.0%) agreed closely with USEPA technical literature but were higher in samples from the pond, soils, and treatment facilities (33.3%, 38.0%, and 48.8%, respectively). Sequencing of false-positive isolates confirmed that most were, l...
The California State Water Resources Control Board is the first regulatory body in the United Sta... more The California State Water Resources Control Board is the first regulatory body in the United States to develop statewide regulations for direct potable reuse (DPR). To support this effort, a pathogen monitoring campaign was undertaken to develop and implement an optimized standard operating protocol to better characterize the concentration of human pathogens in raw wastewater. Methods to detect relevant viral and protozoan pathogens in raw wastewater were optimized and implemented during a 14-month monitoring campaign. Over 120 samples were collected from five wastewater treatment plants treating a quarter of California's population. Samples were analyzed for two protozoa (Cryptosporidium and Giardia) using microscopy methods, three enteric viruses (enterovirus, adenovirus, and norovirus) using culture and/or molecular methods, and male-specific coliphage using culture methods. The method recovery efficiency was measured in every protozoa sample and every other virus sample to confirm minimum recovery efficiencies were achieved and to correct the concentrations for pathogen losses during sample processing. The results from this study provide the industry with a large, high-quality dataset as demonstrated by the high degree of method sensitivity, method recovery, and QA/QC steps. Such high-quality data on pathogen concentrations in raw wastewater are critical for confirming the level of treatment needed to reduce pathogen concentrations down to acceptable levels for potable water in DPR projects.
Pathogen contamination of agricultural water has been identified as a probable cause of recalls a... more Pathogen contamination of agricultural water has been identified as a probable cause of recalls and outbreaks. However, variability in pathogen presence and concentration complicates the reliable identification of agricultural water at elevated risk of pathogen presence. In this study, we collected data on the presence of Salmonella and genetic markers for enterohemorrhagic E. coli (EHEC; PCR-based detection of stx and eaeA) in southwestern US canal water, which is used as agricultural water for produce. We developed and assessed the accuracy of models to predict the likelihood of pathogen contamination of southwestern US canal water. Based on 169 samples from 60 surface water canals (each sampled 1–3 times), 36% (60/169) and 21% (36/169) of samples were positive for Salmonella presence and EHEC markers, respectively. Water quality parameters (e.g., generic E. coli level, turbidity), surrounding land-use (e.g., natural cover, cropland cover), weather conditions (e.g., temperature), ...
We have all heard the saying “food grows where water flows,” but in the Western United States, ag... more We have all heard the saying “food grows where water flows,” but in the Western United States, agriculture’s share of freshwater supplies have been under pressure. This has been especially true in parts of Arizona, where the majority of the state was classified as suffering moderate to severe drought conditions in June 2014 (ADWR, 2014a). Lack of precipitation, combined with widespread urbanization of farmland has stimulated the transfer of water rights away from agriculture. But in turn, urbanization has also accelerated an increase in a completely new source of irrigation water: recycled municipal wastewater, defined by the Arizona Legislature as “water that has been treated or processed by a wastewater treatment plant or an on-site wastewater treatment facility” (AZLEG, 2014).
Pre harvest irrigation water represents a key potential source of pathogenic bacteria during the ... more Pre harvest irrigation water represents a key potential source of pathogenic bacteria during the production of fresh produce. Industry guidance metrics uniformly identify generic Escherichia coli (E. coli) as a practical and cost‐effective indicator of fecal contamination in water. Although generic E. coli satisfies most characteristics of an ideal bacterial indicator, very limited correlation exists between the presence of E. coli, pathogen presence, and microbial risk to consumers following consumption. The Food Safety Modernization Act’s Produce Safety Rule’s Microbial Water Quality Profile is under abeyance due to concerns that there is not enough scientific evidence to support the rule in its’ current form; thus, it is important to examine feasible alternative indicator organisms which could improve agricultural water quality assessment and the protection of public health. This work examines the bacterial group, Bacteroides for prediction of pathogens in irrigation water sample...
Environmental Science: Water Research & Technology, 2020
Brian Pecson and Daniel Gerrity present an Editorial Perspective which focuses on the impact of S... more Brian Pecson and Daniel Gerrity present an Editorial Perspective which focuses on the impact of SARS-CoV-2 on the water industry.
Agricultural water is an important source of foodborne pathogens on produce farms. Managing water... more Agricultural water is an important source of foodborne pathogens on produce farms. Managing water-associated risks does not lend itself to one-size-fits-all approaches due to the heterogeneous nature of freshwater environments. To improve our ability to develop location-specific risk management practices, a study was conducted in two produce-growing regions to (i) characterize the relationship between Escherichia coli levels and pathogen presence in agricultural water, and (ii) identify environmental factors associated with pathogen detection. Three AZ and six NY waterways were sampled longitudinally using 10-L grab samples (GS) and 24-h Moore swabs (MS). Regression showed that the likelihood of Salmonella detection (Odds Ratio [OR] = 2.18), and eaeA-stx codetection (OR = 6.49) was significantly greater for MS compared to GS, while the likelihood of detecting L. monocytogenes was not. Regression also showed that eaeA-stx codetection in AZ (OR = 50.2) and NY (OR = 18.4), and Salmonella detection in AZ (OR = 4.4) were significantly associated with E. coli levels, while Salmonella detection in NY was not. Random forest analysis indicated that interactions between environmental factors (e.g., rainfall, temperature, turbidity) (i) were associated with likelihood of pathogen detection and (ii) mediated the relationship between E. coli levels and likelihood of pathogen detection. Our findings suggest that (i) environmental heterogeneity, including interactions between factors, affects microbial water quality, and (ii) E. coli levels alone may not be a suitable indicator of food safety risks. Instead, targeted methods that utilize environmental and microbial data (e.g., models that use turbidity and E. coli levels to predict when there is a high or low risk of surface water being contaminated by pathogens) are needed to assess and mitigate the food safety risks associated with preharvest water use. By identifying environmental factors associated with an increased likelihood of detecting pathogens in agricultural
Current Opinion in Environmental Science & Health, 2020
Abstract Despite the global push for a circular water and nutrient economy, the United States sti... more Abstract Despite the global push for a circular water and nutrient economy, the United States still lags in recycling and reusing valuable waste streams. The reuse of waste streams could result in more sustainable agricultural practices by reducing water withdrawals in stressed environments and nutrient inputs to eutrophication-impacted ecosystems. However, microbial risks are a key barrier to reuse. We identify research and regulatory gaps through a systematic review of quantitative microbial risk assessments (QMRAs) and regulations for biosolids, manure, and human source-separated urine. We propose a cohesive path forward to improve upon existing QMRA approaches, to combine QMRA with other risk frameworks, and to develop integrated monitoring and control strategies by incorporating molecular biology tools. The application of a farm-to-fork risk-based approach that considers the combined use of waste streams is needed to develop comprehensive best management practices, treatment recommendations, and microbial quality criteria that promote food safety while advancing agricultural sustainability.
Сборник содержит статьи Всероссийской научно-практической конференции «Архивы в истории. История ... more Сборник содержит статьи Всероссийской научно-практической конференции «Архивы в истории. История в архивах», посвященной 100-летию Государственной архивной службы России, 95-летию архивной службы Республики Бурятия и 140-летию В.П. Гирченко, историка, архивиста, организатора архивного дела в Бурятии (7 июня 2018 г., г. Улан-Удэ). Тематика статей охватывает исследования по истории становления архивного дела в России, социальной роли архивов и значения архивных документов в сохранении исторической памяти. Адресовано широкому кругу читателей, интересующихся историей и современной жизнью региона.
Treatment of wastewater for potable reuse requires the reduction of enteric viruses to levels tha... more Treatment of wastewater for potable reuse requires the reduction of enteric viruses to levels that pose no significant risk to human health. Advanced water treatment trains (e.g., chemical clarification, reverse osmosis, ultrafiltration, advanced oxidation) have been developed to provide reductions of viruses to differing levels of regulatory control depending upon the levels of human exposure and associated health risks. Importance in any assessment is information on the concentration and types of viruses in the untreated wastewater, as well as the degree of removal by each treatment process. However, it is critical that the uncertainty associated with virus concentration and removal or inactivation by wastewater treatment be understood to improve these estimates and identifying research needs. We reviewed the critically literature to assess to identify uncertainty in these estimates. Biological diversity within families and genera of viruses (e.g. enteroviruses, rotaviruses, adeno...
Bacteria can grow in the presence of trimethoprim and sulfamethoxazole by expressing antibiotic r... more Bacteria can grow in the presence of trimethoprim and sulfamethoxazole by expressing antibiotic resistance genes or by acquiring thymine or thymidine from environmental reservoirs to facilitate DNA synthesis. The purpose of this study was to evaluate whether activated sludge serves as a reservoir for thymine or thymidine, potentially impacting the quantification of antibiotic resistant bacteria. This study also assessed the impacts of varying solids retention time (SRT) on trimethoprim and sulfamethoxazole removal during wastewater treatment and single and multi-drug resistance. When assayed in the presence of the antibiotics at standard clinical concentrations, up to 40% increases in the relative prevalence of resistant bacteria were observed with (1) samples manually augmented with reagent-grade thymidine, (2) samples manually augmented with sonicated biomass (i.e., cell lysate), (3) samples manually augmented with activated sludge filtrate, and (4) activated sludge samples collected from reactors with longer SRTs. These observations suggest that longer SRTs may select for antibiotic resistant bacteria and/or result in false positives for antibiotic resistance due to higher concentrations of free thymine, thymidine, or other extracellular constituents.
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