Incorporating expert judgments in utility evaluation of bacteroidales qPCR assays for microbial source tracking in a drinking water source

Microbe-sediment interactions in Great Lakes recreational waters: Implications for human health risk

Microbial assessments of recreational water have traditionally focused on culturing or DNA-based approaches of the planktonic water column, omitting influence from microbe-sediment relationships. Sediment (bed and suspended) has been shown to often harbour levels of bacteria higher than the planktonic phase. The fate of suspended sediment (SS) bacteria is extensively related to transport dynamics (e.g., deposition) of the associated sediment/floc. When hydraulic energy allows, SS will settle, introducing new (potentially pathogenic) organisms to the bed. With turbulence, including waves, currents and swimmers, the risk of human ingestion is elevated due to resuspension of bed sediment and associated microbes. This research used multiplex nanofluidic reverse transcriptase quantitative PCR on RNA of bacteria associated with bed and SS to explore the active bacteria in freshwater shorelines. Bacterial genes of human health concern regarding recreational water use were targeted, such as faecal indicator bacteria (FIB), microbial source tracking genes and virulence factors from waterborne pathogens. Results indicate avian sources (i.e., gulls, geese) to be the largest nonpoint source of FIB associated with sediment in Great Lakes shorelines. This research introduces a novel approach to microbial water quality assessments and enhances our understanding of microbe-sediment dynamics and the quality of freshwater beaches.

Integrating Bayesian Analysis and Cumulative Probability Generates High Confidence Using a Single Microbial Source Tracking Marker

Microbial source tracking can identify waterbodies at risk of contamination using host-associated molecular markers. No assay used for microbial source tracking is both 100% host-specific and sensitive for human or animal fecal contamination. Using literature sensitivity and specificity values, Bayes' Theorem for conditional probability was applied to the human fecal-associated HF183 marker in a microbial source tracking context. Type I and Type II error rates were examined across a range of priors. Conditional probabilities were investigated using two human-associated markers, HF183 and HumM2, concurrently. Cumulative probability analysis was used to explore the likelihood of true contaminant detection using multiple samples. Probability of human fecal contamination was calculated for all combinations of positive and negative marker results given three samples. Results demonstrate the respective influence that specificity and sensitivity values exert on the likelihood of true positive and true negative. Using practical priors, high levels of confidence (99%) in results were observed when HF183 and HumM2 were used concurrently. Cumulative probability analyses showed that multiple samples from a single location can provide a >95% level of confidence in positive and negative results, suggesting that when multiple samples are necessary to account for in situ variability, a single marker can yield sufficiently reliable results.

Occurrence of heavy metals and contaminants on the surface of adjacent rivers

Water is fundamental to the survival of living beings. It registers every impact and can function as an indicator of environmental stressors. Our objective in the current study was to assess the sanitary conditions of the waters in the Açude, Maria Lucinda and Santa Rosa streams. This was done by checking pH, running quantitative analyses of heavy metals and testing for total coliforms. The effect of ultraviolet (UV) rays on samples positive for coliforms was evaluated. The average pH of the streams ranged between 4 and 7 and changed between drought and rainy season conditions. Chromium and nickel values were above those permitted by the Brazilian National Council on the Environment, CONAMA. In the dry season, zinc values were above those established by CONAMA for waterbodies of Classes 1 and 2. Thermotolerant coliforms were present in all samples collected and above permitted values. After exposing the bacteria to UV light, it was noted that UV irradiation was unable to decrease the bacteria count. Ninety residents who use stream water were interviewed: 24% of interviewees said they use the waters of the Açude and Mary Lucinda streams and along the Santa Rosa stream, 95% of inhabitants said they use the water.

Water quality at points-of-use in the Galapagos Islands

Piped drinking water is often considered a gold standard for protecting public health but research is needed to explicitly evaluate the effect of centralized treatment systems on water quality in developing world settings. This study examined the effect of a new drinking water treatment plant (DWTP) on microbial drinking water quality at the point-of-use on San Cristobal Island, Galapagos using fecal indicator bacteria total coliforms and Escherichia coli. Samples were collected during six collection periods before and after operation of the DWTP began from the freshwater sources (n=4), the finished water (n=6), and 50 sites throughout the distribution system (n=287). This study found that there was a significant decrease in contamination by total coliforms (two orders of magnitude) and E. coli (one order of magnitude) after DWTP operation began (p<0.001). However, during at least one post-construction collection cycle, total coliforms and E. coli were still found at 66% and 28% of points-of-use (n=50), respectively. During the final collection period, conventional methods were augmented with human-specific Bacteroides assays - validated herein - with the goal of elucidating possible microbial contamination sources. Results show that E. coli contamination was not predictive of contamination by human wastes and suggests that observed indicator bacteria contamination may have environmental origins. Together these findings highlight the necessity of a holistic approach to drinking water infrastructure improvements in order to deliver high quality water through to the point-of-use.

Microbial source tracking of private well water samples across at-risk regions in southern Ontario and analysis of traditional fecal indicator bacteria assays including culture and qPCR

Many people living in rural areas rely on privately owned wells as their primary source of drinking water. These water sources are at risk for fecal contamination of human, wildlife, and livestock origin. While traditional bacteriological testing involves culture-based methods, microbial source tracking (MST) assays present an opportunity to additionally determine the source of fecal contamination. This study investigated the main host sources of contamination in private well water samples with high levels of Escherichia coli (E. coli), using MST with human and multi-species specific markers. Fecal contamination of human origin was detected in approximately 50% of samples, indicating that current contamination prevention strategies require reconsideration. The relationship between cattle density and fecal contamination of bovine origin was investigated using a Bovine Bacteroidales specific MST assay. Regional variations of microbial sources were examined, and may inform local primary prevention strategies. Additionally, in order to assess MST and E. coli quantitative real time polymerase chain reaction (qPCR) assays as indicators of fecal contamination, these were compared to E. coli culture methods. Variation in results was observed across all assay methods investigated, suggesting the most appropriate routine bacteriological testing methodology cannot be determined without comparison to a method that directly detects the presence of fecal contamination.

Predicting microbial water quality with models: Over-arching questions for managing risk in agricultural catchments

The application of models to predict concentrations of faecal indicator organisms (FIOs) in environmental systems plays an important role for guiding decision-making associated with the management of microbial water quality. In recent years there has been an increasing demand by policy-makers for models to help inform FIO dynamics in order to prioritise efforts for environmental and human-health protection. However, given the limited evidence-base on which FIO models are built relative to other agricultural pollutants (e.g. nutrients) it is imperative that the end-user expectations of FIO models are appropriately managed. In response, this commentary highlights four over-arching questions associated with: (i) model purpose; (ii) modelling approach; (iii) data availability; and (iv) model application, that must be considered as part of good practice prior to the deployment of any modelling approach to predict FIO behaviour in catchment systems. A series of short and longer-term research priorities are proposed in response to these questions in order to promote better model deployment in the field of catchment microbial dynamics.

Utility of Helicobacter spp. associated GFD markers for detecting avian fecal pollution in natural waters of two continents

Avian fecal droppings may negatively impact environmental water quality due to the presence of high concentrations of fecal indicator bacteria (FIB) and zoonotic pathogens. This study was aimed at evaluating the performance characteristics and utility of a Helicobacter spp. associated GFD marker by screening 265 fecal and wastewater samples from a range of avian and non-avian host groups from two continents (Brisbane, Australia and Florida, USA). The host-prevalence and -specificity of this marker among fecal and wastewater samples tested from Brisbane were 0.58 and 0.94 (maximum value of 1.00). These values for the Florida fecal samples were 0.30 (host-prevalence) and 1.00 (host-specificity). The concentrations of the GFD markers in avian and non-avian fecal nucleic acid samples were measured at a test concentration of 10 ng of nucleic acid at Brisbane and Florida laboratories using the quantitative PCR (qPCR) assay. The mean concentrations of the GFD marker in avian fecal nucleic acid samples (5.2 × 10(3) gene copies) were two orders of magnitude higher than non-avian fecal nucleic acid samples (8.6 × 10(1) gene copies). The utility of this marker was evaluated by testing water samples from the Brisbane River, Brisbane and a freshwater creek in Florida. Among the 18 water samples tested from the Brisbane River, 83% (n = 18) were positive for the GFD marker, and the concentrations ranged from 6.0 × 10(1)-3.2 × 10(2) gene copies per 100 mL water. In all, 92% (n = 25) water samples from the freshwater creek in Florida were also positive for the GFD marker with concentrations ranging from 2.8 × 10(1)-1.3 × 10(4) gene copies per 100 mL water. Based on the results, it can be concluded that the GFD marker is highly specific to avian host groups, and could be used as a reliable marker to detect the presence and amount of avian fecal pollution in environmental waters.

LA35 Poultry Fecal Marker Persistence Is Correlated with That of Indicators and Pathogens in Environmental Waters

Disposal of fecally contaminated poultry litter by land application can deliver pathogens and fecal indicator bacteria (FIB) into receiving waters via runoff. While water quality is regulated by FIB enumeration, FIB testing provides inadequate information about contamination source and health risk. This microbial source tracking (MST) study compared the persistence of the Brevibacterium sp. strain LA35 16S rRNA gene (marker) for poultry litter with that of pathogens and FIB under outdoor, environmentally relevant conditions in freshwater, marine water, and sediments over 7 days. Salmonella enterica, Campylobacter jejuni, Campylobacter coli, Bacteroidales, and LA35 were enumerated by quantitative PCR (qPCR), and Enterococcus spp. and E. coli were quantified by culture and qPCR. Unlike the other bacteria, C. jejuni was not detectable after 48 h. Bacterial levels in the water column consistently declined over time and were highly correlated among species. Survival in sediments ranged from a slow decrease over time to growth, particularly in marine microcosms and for Bacteroidales. S. enterica also grew in marine sediments. Linear decay rates in water (k) ranged from -0.17 day(-1) for LA35 to -3.12 day(-1) for C. coli. LA35 levels correlated well with those of other bacteria in the water column but not in sediments. These observations suggest that, particularly in the water column, the fate of LA35 in aquatic environments is similar to that of FIB, C. coli, and Salmonella, supporting the hypothesis that the LA35 marker gene can be a useful tool for evaluating the impact of poultry litter on water quality and human health risk.