Coli Loads Research Articles

Oral administration of a 2-aminopyrimidine robenidine analogue (NCL195) significantly reduces Staphylococcus aureus infection and reduces Escherichia coli infection in combination with sub-inhibitory colistin concentrations in a bioluminescent mouse model.

We have previously reported promising in vivo activity of the first-generation 2-aminopyramidine robenidine analogue NCL195 against Gram-positive bacteria (GPB) when administered via the systemic route. In this study, we examined the efficacy of oral treatment with NCL195 (± low-dose colistin) in comparison to oral moxifloxacin in bioluminescent Staphylococcus aureus and Escherichia coli peritonitis-sepsis models. Four oral doses of 50 mg/kg NCL195, commencing immediately post-infection, were administered at 4 h intervals in the S. aureus peritonitis-sepsis model. We used a combination of four oral doses of 50 mg/kg NCL195 and four intraperitoneal doses of colistin at 0.125 mg/kg, 0.25 mg/kg, or 0.5 mg/kg in the E. coli peritonitis-sepsis model. Subsequently, the dose rates of four intraperitoneal doses of colistin were increased to 0.5 mg/kg, 1 mg/kg, or 2 mg/kg at 4 h intervals to treat a colistin-resistant E. coli infection. In the S. aureus infection model, oral treatment of mice with NCL195 resulted in significantly reduced S. aureus infection loads (P < 0.01) and longer survival times (P < 0.001) than vehicle-only treated mice. In the E. coli infection model, co-administration of NCL195 and graded doses of colistin resulted in a dose-dependent significant reduction in colistin-susceptible (P < 0.01) or colistin-resistant (P < 0.05) E. coli loads compared to treatment with colistin alone at similar concentrations. Our results confirm that NCL195 is a potential candidate for further preclinical development as a specific treatment for multidrug-resistant infections, either as a stand-alone antibiotic for GPB or in combination with sub-inhibitory concentrations of colistin for Gram-negative bacteria.

Assessing Changes in Bacterial Load and Antibiotic Resistance in the Legon Sewage Treatment Plant between 2018 and 2023 in Accra, Ghana.

Wastewater treatment plants are efficient in reducing bacterial loads but are also considered potential drivers of environmental antimicrobial resistance (AMR). In this study, we determined the effect of increased influent wastewater volume (from 40% to 66%) in the Legon sewage treatment plant (STP) on the removal of E. coli from sewage, along with changes in AMR profiles. This before and after study compared E. coli loads and AMR patterns in influent and effluent samples from a published baseline study (January-June 2018) with a follow-up study (March-May 2023). Extended-spectrum beta-lactamase (ESBL) E. coli were measured pre- and post-sewage treatment during the follow-up study. The follow-up study showed 7.4% and 24% ESBL E. coli proportions in influent and effluent, respectively. In both studies, the STP was 99% efficient in reducing E. coli loads in effluents, with no significant difference (p = 0.42) between the two periods. More E. coli resistance to antimicrobials was seen in effluents in the follow-up study versus the baseline study. The increased influent capacity did not reduce the efficiency of the STP in removing E. coli from influent wastewater but was associated with increased AMR patterns in effluent water. Further studies are required to determine whether these changes have significant effects on human health.

Physicochemical parameters, organoleptic property, and Escherichia coli load of fresh turkey organs

Escherichia coli is a common microorganism of the digestive microflora of many warm-blooded animal species, including humans. The presence of E. coli in food is an indicator of faecal contamination and ultimately, possible contamination by pathogenic digestive microflora. The aim of the present work was to study the physicochemical parameters, organoleptic property, and E. coli load in turkey organs (thigh, upper thigh, breast, throat, liver, wing, and skin). A total of 224 samples were purchased from several markets, and subjected to different experiments. Results showed that the best overall scores for organoleptic property were recorded for breast (8.64 ± 0.43) and upper thigh (7.12 ± 0.72). The physicochemical parameter results varied across the studied organs. E. coli was isolated up to 100, 93.75, 90.62, 87.50, 62.5, 56.25, and 40.62% in the skin, wing, throat, liver, thigh, breast, and upper thigh samples, respectively. The highest E. coli loads were recorded in the skin, throat, and wing at 3.89, 3.52, and 3.27 log10 CFU/g, respectively. The present work highlighted the physicochemical parameters, organoleptic property, and E. coli load of turkey organs purchased from several districts of Kenitra city, and discussed a number of practices to improve turkey meat quality and protect consumer health from coliform contamination.

Monitoring the Influence of Anthropogenic Pollution on the Quality of Irrigation Water for Market Gardening in Yamoussoukro, Côte d’Ivoire

Background: The microbiological quality of three vegetable crops (cabbages, carrots, lettuces) and their irrigation water from the lake system of the city of Yamoussoukro were studied. The pollution indicator used is Escherichia coli (E. coli), of the thermotolerant coliform family. Methods: During the period 2017-2019, in four dry and four wet seasons, a total of 744 water samples and 13392 vegetable samples were collected in five (5) lakes belonging to the lake system. The lakes were selected because of their position in the system. The E. coli loads were evaluated after isolation on a specific COMPASS ECC Agar and confirmed with Polymerase chain reaction (PCR) and the physicochemical parameters of the lakes, evaluated according to their respective ISO standards. Result: In irrigation waters, bacterial loads and physico-chemical parameters generally have evolved from the upstream lakes to those downstream of the lake system (from lake A to lake E). Values were higher during the rainy seasons. E. coli loads on vegetables were strongly correlated with those of irrigation water, especially in dry seasons. Spearman’s correlations revealed significant correlations between turbidity, DOC and bacterial loads. The risk of bacterial transmission between lake waters and surrounding vegetables is proven.

Experimental and modelling evidence of splash effects on manure borne Escherichia coli washoff.

In tropical montane South-East Asia, recent changes in land use have induced increased runoff, soil erosion and in-stream suspended sediment loads. Land use change is also contributing to increased microbial pathogen dissemination and contamination of stream waters. Escherichia coli (E. coli) is frequently used as an indicator of faecal contamination. Field rain simulations were conducted to examine how E. coli is exported from the surface of upland, agricultural soils during runoff events. The objectives were to characterize the loss dynamics of this indicator from agricultural soils contaminated with livestock waste, and to identify the effect of splash on washoff. Experiments were performed on nine 1 m2 plots, amended or not with pig or poultry manure. Each plot was divided into two 0.5 m2 sub-plots. One of the two sub-plots was protected with a mosquito net for limiting the raindrop impact effects. Runoff, soil detachment by raindrop impact and its entrainment by runoff, and E. coli loads and discharge were measured for each sub-plot. The results show that raindrop impact strongly enhances runoff generation, soil detachment and entrainment and E. coli export. When the impact of raindrops was reduced with a mosquito net, total runoff was reduced by more than 50%, soil erosion was on average reduced by 90% and E. coli export from the amended soil surface was on average 3 to 8 times lower. A coupled physics-based approach was performed using the Cast3M platform for modelling the time evolutions of runoff, solid particles detachment and transfer and bacteria transport that were measured for one of the nine plots. After estimation of the saturated hydraulic conductivity, soil erodibility and attachment rate of bacteria, model outputs were consistent with measured runoff coefficients, suspended sediment and E. coli loads. This work therefore underlines the need to maintain adequate vegetation at the soil surface to avoid the erosion and export of soil borne potential pathogens towards downstream aquatic systems.

Do reductions in agricultural field drainage during the growing season impact bacterial densities and loads in small tile-fed watersheds?

Predicting bacterial levels in watersheds in response to agricultural beneficial management practices (BMPs) requires understanding the germane processes at both the watershed and field scale. Controlling subsurface tile drainage (CTD) is a highly effective BMP at reducing nutrient losses from fields, and watersheds when employed en masse, but little work has been conducted on CTD effects on bacterial loads and densities in a watershed context. This study compared fecal indicator bacteria (FIB) [E. coli, Enterococcus, Fecal coliform, Total coliform, Clostridium perfringens] densities and unit area loads (UAL) from a pair of flat tile-drained watersheds (∼250–467 ha catchment areas) during the growing season over a 10−year monitoring period, using a before-after-control-impact (BACI) design (i.e., test CTD watershed vs. reference uncontrolled tile drainage (UCTD) watershed during a pre CTD intervention period and a CTD-intervention period where the test CTD watershed had CTD deployed on over 80% of the fields). With no tile drainage management, upstream tile drainage to ditches comprised ∼90% of total ditch discharge. We also examined FIB loads from a subset of tile drained fields to determine field load contributions to the watershed drainage ditches. Statistical evidence of a CTD effect on FIB UAL in the surface water systems was not strong; however, there was statistical evidence of increased FIB densities [pronounced when E. coli >200 most probable number (MPN) 100 mL−1] in the test CTD watershed during the CTD-intervention period. This was likely a result of reduced dilution/flushing in the test CTD watershed ditch due to CTD significantly decreasing the amount of tile drainage water entering the surface water system. Tile E. coli load contributions to the ditches were low; for example, during the 6-yr CTD-intervention period they amounted to on average only ∼3 and ∼9% of the ditch loads for the test CTD and reference UCTD watersheds, respectively. This suggests in-stream, or off-field FIB reservoirs and bacteria mobilization drivers, dominated ditch E. coli loads in the watersheds during the growing season. Overall, this study suggested that decision making regarding deployment of CTD en masse in tile-fed watersheds should consider drainage practice effects on bacterial densities and loads, as well as CTD's documented capacity to boost crop yields and reduce seasonal nutrient pollution.

Contributions of combined sewer overflows and treated effluents to the bacterial load released into a coastal area

The impact of combined sewer overflow (CSO) on the receiving water body is an issue of increasing concern, as it may lead to restrictions in the use and destination of the receiving body, such as bathing or recreational area closures, fish and shellfish consumption restrictions, and contamination of drinking water resources. Recent investigations have mainly referred to the occurrence and loads of suspended solids, organic compounds and, in some cases, micropollutants. Attempts have been made to find correlations between the discharged load and the size and characteristics of the catchment area, climate conditions, rainfall duration and intensity.This study refers to a touristic coastal area in the north-east of Italy, which is characterized by a combined sewer network including 5 CSO outfalls which, in the case of heavy rain events, directly discharge the exceeding water flow rate into channels which, after a short distance, reach the Adriatic Sea. The study analyzed: i) rainfall events during the summer period in 2014 which led to overflow in the different outfalls, ii) the inter- and intra-event variability with regard to E. coli, Enterococci and conductivity, and iii) the hydraulic and pollutant (E. coli and Enterococci) loads discharged by the local wastewater treatment plant and by all the CSO outfalls. Finally, it estimated the contribution of each source to the released hydraulic and pollutant loads into the receiving water body. Moreover, it was also found that the modest water volume discharged by all CSO outfalls (only 8% of the total volume discharged by the area) contains >90% of the microbial load.

Effect of land use and hydrological processes on Escherichia coli concentrations in streams of tropical, humid headwater catchments.

Lack of access to clean water and adequate sanitation continues to be a major brake on development. Here we present the results of a 12-month investigation into the dynamics of Escherichia coli, a commonly used indicator of faecal contamination in water supplies, in three small, rural catchments in Laos, Thailand and Vietnam. We show that land use and hydrology are major controlling factors of E. coli concentrations in streamwater and that the relative importance of these two factors varies between the dry and wet seasons. In all three catchments, the highest concentrations were observed during the wet season when storm events and overland flow were highest. However, smaller peaks of E. coli concentration were also observed during the dry season. These latter correspond to periods of intense farming activities and small, episodic rain events. Furthermore, vegetation type, through land use and soil surface crusting, combined with mammalian presence play an important role in determining E. coli loads in the streams. Finally, sampling during stormflow revealed the importance of having appropriate sampling protocols if information on maximum contamination levels is required as grab sampling at a fixed time step may miss important peaks in E. coli numbers.

Changes in the Abundance of Faecalibacterium prausnitzii Phylogroups I and II in the Intestinal Mucosa of Inflammatory Bowel Disease and Patients with Colorectal Cancer.

Faecalibacterium prausnitzii comprises 2 phylogroups, whose abundance in healthy and diseased gut and in conjunction with Escherichia coli has not yet been studied. This work aims to determine the contribution of F. prausnitzii phylogroups I and II in intestinal disease and to assess their potential diagnostic usefulness as biomarkers for gut diseases. Total F. prausnitzii, its phylogroups, and E. coli loads were determined by quantitative polymerase chain reaction targeting the 16S rRNA gene on biopsies from 31 healthy controls (H), 45 patients with Crohn's disease (CD), 25 patients with ulcerative colitis, 10 patients with irritable bowel syndrome, and 20 patients with colorectal cancer. Data were normalized to total bacterial counts and analyzed according to patients' disease location and clinical characteristics. Lower levels of both total F. prausnitzii and phylogroup I were found in subjects with CD, ulcerative colitis, and colorectal cancer (P < 0.001) compared with H subjects. Phylogroup I load was a better biomarker than total F. prausnitzii to discriminate subjects with gut disorders from H. Phylogroup II depletion was observed only in patients with CD (P < 0.001) and can be potentially applied to differentiate ulcerative pancolitis from colonic CD. No statistically significant correlation between E. coli and any of the 2 F. prausnitzii phylogroups was found in any group of patients or by inflammatory bowel disease location. Phylogroup I was lower in active patients with CD, whereas those CD with intestinal resection showed a reduction in phylogroup II. Treatments with mesalazine and immunosuppressants did not result in the recovery of F. prausnitzii phylogroups abundance. F. prausnitzii phylogroup I was depleted in CD, ulcerative colitis, and colorectal cancer, whereas phylogroup II was specifically reduced in CD. Quantification of F. prausnitzii phylogroups and E. coli may help to identify gut disorders and to classify inflammatory bowel disease location.

Recent Applications of Spectroscopic and Hyperspectral Imaging Techniques with Chemometric Analysis for Rapid Inspection of Microbial Spoilage in Muscle Foods

AbstractMuscle food is one of the most perishable food products because of its vulnerability to microbial spoilage, which can result in critical food safety problems. Traditional techniques for detection and evaluation of microbial spoilage in muscle foods are tedious, laborious, destructive, and time‐consuming. In recent years, spectroscopic and imaging technologies have shown great potentials for the assessment of food quality and safety due to their nondestructive, noninvasive, cost‐effective, and rapid responsive nature. This review focuses on the applications of several valuable spectroscopic techniques including visible and near‐infrared spectroscopy, Fourier transform infrared spectroscopy, fluorescence spectroscopy, Raman spectroscopy, and hyperspectral imaging for the rapid and nondestructive detection of microbial spoilage in common muscle foods such as meat, poultry, fish, and related products. Combined with chemometric analysis, such as spectral preprocessing and modeling methods, these potential technologies have been successfully developed for the determination of total viable count, aerobic plate count, Enterobacteriaceae, Pseudomonas, Escherichia coli, and lactic acid bacteria loads in muscle foods. Moreover, the advantages and disadvantages of these techniques are discussed and some perspectives about future trends are also presented.

Quantifying faecal indicator organism hydrological transfer pathways and phases in agricultural catchments

Faecal indicator organisms (FIOs) can impact on water quality and pose a health and environmental risk. The transfer of FIOs, such as Escherichia coli (E. coli), from land to water is driven by hydrological connectivity and may follow the same flowpaths as nutrients, from agricultural and human sources. This study investigated E. coli transfer in two catchment areas with high source and transport pressures. These pressures were: organic phosphorus (P) loading; human settlement; conduits and fissures in a grassland karst area; and clay rich and impermeable soils in a mixed arable area. The occurrence of E. coli and its transport pathways, along with the pathways of nutrients, were studied using a combination of targeted FIO sampling, during different hydrological phases and events, and high resolution nutrient analysis. The quick flow component in both catchments was found to be a more potent vector for E. coli, and was coincident with the total P flowpaths using a P Loadograph Recession Analysis (LRA). The karst grassland catchment was found to be a transport limited system and the mixed arable catchment a source limited system. Hence, despite the grassland catchment being a potentially higher FIO source, the E. coli loads leaving the catchment were low compared to the mixed arable catchment. E. coli load whole-event comparisons also indicated that the grassland karst transfers tended to be much lower on falling phases of runoff, while the arable catchment, over greywacke and mudstone geology, showed little change between the phases. Furthermore, the arable catchment showed asymptotic decline of sustained E. coli loads towards low flows, which may be indicative of chronic point sources. These results indicate the dominance of transport mechanisms over source mechanisms for mass E. coli loads and also chronic loads during low flow. These will be important considerations for risk assessment and mitigation.

Rapid Quantification Analysis and Visualization of Escherichia coli Loads in Grass Carp Fish Flesh by Hyperspectral Imaging Method

Microbial contamination during fish flesh spoilage process can easily induce food-borne outbreaks and consumer health problems. Hyperspectral imaging in the spectral range of 400–1000 nm was developed to measure the Escherichia coli (E. coli) loads in grass carp fish for evaluation and visualization of microbial spoilage. Partial least square regression (PLSR) model was conducted to build prediction models between the spectral data and the reference E. coli loads estimated by classical microbiological plating method. The PLSR model based on full wavelengths showed good performance on predicting E. coli loads with the residual predictive deviation (RPD) of 5.47 and determination coefficient of R2P = 0.880. Six characteristic wavelengths were selected by the weighted regression coefficients from PLSR analysis and used to simplify the models. The simplified PLSR and multiple linear regression (MLR) models also presented good prediction capability. The better simplified MLR model (RPD = 5.22 and R2P = 0.870) was used to transfer each pixel in the image for visualizing the spatial distribution of E. coli loads. The results demonstrated that hyperspectral imaging technique with multivariate analysis has the potential to rapidly and non-invasively quantify and visualize the E. coli loads in grass carp fish flesh during the spoilage process.

Temporal analysis of E. coli, TSS and wastewater micropollutant loads from combined sewer overflows: implications for management.

A combined sewer overflow (CSO) outfall was monitored to assess the impact of temporal mass loads on the appropriateness of treatment options. Instantaneous loads (mass per s) varied by approximately three orders of magnitude during events (n = 9 in spring, summer and the fall) with no significant seasonal variations. The median fraction of total loads discharged with the first 25% of the total volume ranged from 28% (theophylline) to 40% (Total Suspended Solids (TSS)) and loads remained high for the duration of the events. E. coli and TSS loads originated primarily from wastewater (WW) (63% and 75%, respectively). However, a mix of stormwater (SW) and sewer deposit (SD) resuspension contributed from 73 to 95% for the first 50% of the volume discharged of total TSS loads for 2 events. The contribution of SD resuspension was not negligible for Wastewater Micropollutants (WWMPs), especially for carbamazepine. Sustained high loads over the course of CSOs highlight the need to revisit current CSO and SW management strategies that focus on the treatment of early discharge volumes.

Wastewater treatment plants release large amounts of extended-spectrum β-lactamase-producing Escherichia coli into the environment.

The determinants of the spread of extended-spectrum β-lactamase-producing Escherichia coli (ESBLEC) in the community remain unclear. To evaluate its dissemination in the environment, we analyzed the ESBLEC population throughout an urban wastewater network. Samples were collected weekly, over a 10-week period, from 11 sites throughout the wastewater network of Besançon city (France). Total E. coli and ESBLEC loads were determined for each sample. As a control, we analyzed 51 clinical ESBLEC isolates collected at our hospital. We genotyped both environmental and clinical ESBLEC by pulsed-field gel electrophoresis and multilocus sequence typing and identified their blaESBL genes by sequencing. The E. coli load was higher in urban wastewater than in hospital wastewater (7.5 × 10(5) vs 3.5 × 10(5) CFU/mL, respectively). ESBLEC was recovered from almost all the environmental samples and accounted for 0.3% of total E. coli in the untreated water upstream from the wastewater treatment plant (WWTP). The ESBLEC load was higher in hospital wastewater than in community wastewater (27 × 10(3) vs 0.8 × 10(3) CFU/mL, respectively). Treatment by the WWTP eliminated 98% and 94% of total E. coli and ESBLEC, respectively. The genotyping revealed considerable diversity within both environmental and clinical ESBLEC and the overrepresentation of some clonal complexes. Most of the sequence types displayed by the clinical isolates were also found in the environment. CTX-M enzymes were the most common enzymes whatever the origin of the isolates. The treatment at the WWTP led to the relative enrichment of ESBLEC. We estimated that >600 billion of ESBLEC are released into the river Doubs daily and the sludge produced by the WWTP, used as fertilizer, contains 2.6 × 10(5) ESBLEC per gram.

Estimating Escherichia coli loads in streams based on various physical, chemical, and biological factors.

Microbes have been identified as a major contaminant of water resources. Escherichia coli (E. coli) is a commonly used indicator organism. It is well recognized that the fate of E. coli in surface water systems is governed by multiple physical, chemical, and biological factors. The aim of this work is to provide insight into the physical, chemical, and biological factors along with their interactions that are critical in the estimation of E. coli loads in surface streams. There are various models to predict E. coli loads in streams, but they tend to be system or site specific or overly complex without enhancing our understanding of these factors. Hence, based on available data, a Bayesian Neural Network (BNN) is presented for estimating E. coli loads based on physical, chemical, and biological factors in streams. The BNN has the dual advantage of overcoming the absence of quality data (with regards to consistency in data) and determination of mechanistic model parameters by employing a probabilistic framework. This study evaluates whether the BNN model can be an effective alternative tool to mechanistic models for E. coli loads estimation in streams. For this purpose, a comparison with a traditional model (LOADEST, USGS) is conducted. The models are compared for estimated E. coli loads based on available water quality data in Plum Creek, Texas. All the model efficiency measures suggest that overall E. coli loads estimations by the BNN model are better than the E. coli loads estimations by the LOADEST model on all the three occasions (three-fold cross validation). Thirteen factors were used for estimating E. coli loads with the exhaustive feature selection technique, which indicated that six of thirteen factors are important for estimating E. coli loads. Physical factors included temperature and dissolved oxygen; chemical factors include phosphate and ammonia; biological factors include suspended solids and chlorophyll. The results highlight that the LOADEST model estimates E. coli loads better in the smaller ranges, whereas the BNN model estimates E. coli loads better in the higher ranges. Hence, the BNN model can be used to design targeted monitoring programs and implement regulatory standards through TMDL programs.

Estimating Potential E. coli Sources in a Watershed Using Spatially Explicit Modeling Techniques1

Riebschleager, K.J., R. Karthikeyan, R. Srinivasan, and K. McKee, 2012. Estimating Potential E. coli Sources in a Watershed Using Spatially Explicit Modeling Techniques. Journal of the American Water Resources Association (JAWRA) 48(4): 745‐761. DOI: 10.1111/j.1752‐1688.2012.00649.xAbstract: The Spatially Explicit Load Enrichment Calculation Tool (SELECT) was automated to characterize waste and the associated pathogens from various sources within a mixed land use watershed. Potential Escherichia coli loads in Lake Granbury watershed were estimated using spatially variable governing factors, such as land use, soil condition, and distance to streams. A new approach for characterizing E. coli loads resulting from malfunctioning on‐site wastewater treatment systems (OWTSs) was incorporated into SELECT along with the Pollutant Connectivity Factor (PCF) module. The PCF component was applied to identify areas contributing E. coli loads during runoff events by incorporating the influence of potential E. coli loading, runoff potential, and travel distance to waterbodies. Simulation results indicated livestock and wildlife are potential E. coli contributing sources in the watershed. The areas in which these sources are potentially contributing are not currently monitored for E. coli. The bacterial water quality violations seen around Lake Granbury are most likely the result of malfunctioning OWTSs and pet wastes. SELECT results demonstrate the need to evaluate each contributing source separately to effectively allocate site specific best management practices (BMPs) utilizing stakeholder inputs. It also serves as a powerful screening tool for determining areas where detailed investigation is merited.

E. coli Transport through Surface-Connected Biopores Identified from Smoke Injection Tests

Macropores are the primary mechanism by which fecal bacteria from surface-applied manure can be transported into subsurface drains or shallow groundwater bypassing the soil matrix. Limited research has been performed investigating fecal bacteria transport through specific macropores identified in the field. The objective of this research was to better understand how fecal bacteria, using Escherichia coli (E. coli) as an indicator organism, are transported through naturally occurring macropores and potential interactions between the macropore and soil matrix domains in the field under controlled experimental conditions. Direct injection/infiltration tests were conducted in two naturally occurring, surface-connected macropores (biopores) that penetrated to the subsurface drain depth, as identified by smoke tests. Data included total drain flow rate (baseflow rate and biopore flow rate), biopore inflow rate, and Rhodamine WT and E. coli concentrations in the drains. Analysis techniques included determining increases in subsurface drain flow rates due to the infiltration tests and percentage of the injected concentration reaching the subsurface drains after dilution with the drain baseflow. In the absence of data for mechanistic models, empirically based rational polynomial models were compared to the more commonly utilized lognormal distribution for modeling the load rate breakthrough curves. Load estimates were derived from integrated forms of these empirical functions, and percent reductions were calculated for Rhodamine WT and E. coli. Peak total drain flow rates increased nearly two-fold due to direct injection into the biopores. Less than 25% of the initial concentrations injected into the biopores reached the drain after dilution with the baseflow in the drain. Lognormal distributions best fit the Rhodamine WT load rate breakthrough curves (R2 = 0.99 for both biopores) and the E. coli load rate data for one of the biopores (R2 = 0.98). A rational fractional polynomial model that tailed off more slowly best fit the E. coli load rate data for the other biopore (R2 = 0.98). Approximately one log reduction was estimated for E. coli loads due to interaction with the soil profile as water flowed through the tortuous path of the biopores; in other words, the soil surrounding the biopore filtered approximately 90% of the E. coli load that entered the biopore compared to approximately 75% for Rhodamine WT. Considering that applied animal manure can contain millions of bacteria per mL, high concentrations and loads are still possible in the subsurface drain flow if macropores are present.

Development and testing of a model for Micro-Organism Prediction in Urban Stormwater (MOPUS)

Accurate estimation of the levels of microorganisms in urban stormwater is needed for stormwater harvesting and to ensure that our streams and bays are safe for recreational uses. The aim of this research was to develop and test a simple urban stormwater microorganism model (Micro-Organism Prediction in Urban Stormwater – MOPUS) which is spatially lumped and coupled to a rainfall runoff model. The microorganism model has surface and subsurface components to simulate build-up and wash-off of microorganisms from the impervious surfaces of the catchment and the stormwater pipes, respectively. The rainfall-runoff model simulates processes from both pervious and impervious surfaces. Both models are conceptual and represent important processes in a simplified manner, thereby limiting the number of calibration coefficients (five for each model) while maintaining accuracy. The coupled model has been tested using a large Escherichia coli ( E. coli) dataset collected from four urban catchments in Melbourne, Australia. For each catchment, around 20 well sampled pollutographs were available. Reasonably good predictions were obtained at each site for both instantaneous flow rates (Nash Sutcliffe E between 0.62 and 0.89) and E. coli concentrations ( E = 0.25–0.45). Event E. coli peaks ( E = 0.42–0.75), E. coli loads ( E = 0.48–0.86) and event mean E. coli concentrations ( E = 0.56–0.76) were also well estimated. In general, it has been demonstrated that, with further development and testing, MOPUS appears capable of reliable predictions of E. coli discharges from urban stormwater systems, allowing its use as a planning tool for urban catchments.

Stormflow dynamics and loads of Escherichia coli in a large mixed land use catchment

AbstractStorm events are major transporters of faecal microbial contaminants, but few studies have reported storm loads or concentration dynamics in relation to discharge or other pollutants, notably fine sediment. Episodically, high loads of faecal contamination during storm flows impact downstream uses of water bodies, particularly contact recreation and shellfish harvesting. We examined the storm dynamics of Escherichia coli, turbidity and discharge in the mixed land use Motueka catchment (2047 km2; 60% forest and 19% pasture) to gain insights into E. coli sources and transport. We also explored different approaches for calculating E. coli loads. Discharge and field turbidity were recorded continuously, and E. coli concentrations were sampled during events, over a 13‐month period near the mouth of the Motueka River. E. coli loads were estimated by interpolation, averaging estimators and by using linear regression with smearing correction of the log‐transformed variables: discharge, turbidity, and both turbidity and discharge. The annual E. coli load was dominated (∼98%) by export during events. Comparison of monthly monitoring with the intensive storm monitoring campaign suggests that simple stratification of the sampling into storm and baseflow would greatly improve export estimates. E. coli peak concentrations always preceded discharge and turbidity peaks (which had similar timing). Turbidity can be a useful surrogate for faecal microbes in smaller catchments, but in the Motueka turbidity was no better for predicting E. coli concentration than discharge. Runoff from grazed pasture and direct deposition from livestock are probably the ultimate E. coli sources in the Motueka catchment. However, in‐channel stores seem to dominate E. coli dynamics during events and account for the typical feature of bacterial concentrations peaking ahead of discharge and turbidity. This study demonstrates the importance of storm events to faecal microbial loads and shows that E. coli concentration dynamics may contrast with those of turbidity. Copyright © 2009 John Wiley &amp; Sons, Ltd.

Efficacy of Gaseous Chlorine Dioxide as a Sanitizer against Cryptosporidium parvum, Cyclospora cayetanensis, and Encephalitozoon intestinalis on Produce

The efficacy of gaseous chlorine dioxide to reduce parasite and bacterial burden in produce was studied. Basil and lettuce leaves were inoculated with Cryptosporidium parvum and Cyclospora cayetanensis oocysts, Encephalitozoon intestinalis spores, and a cocktail of two isolates of nalidixic acid–resistant Escherichia coli O157:H7. The inoculated samples were then treated for 20 min with gaseous chlorine dioxide at 4.1 mg/liter. Cryptosporidium had a 2.6 and 3.31 most-probable-number log reduction in basil and lettuce, respectively. Reduction of Encephalitozoon in basil and lettuce was 3.58 and 4.58 CFU/g respectively. E. coli loads were significantly reduced (2.45 to 3.97 log), whereas Cyclospora sporulation was not affected by this treatment.