A framework for valuing the health benefits of improved bathing water quality in the River Irvine catchment

A simple model predicting bathing water concentrations of Escherichia coli from livestock in the Irvine catchment in SW Scotland has been adapted for intestinal enterococci (IE). This has been used to predict risk of bather illness by extrapolation of published data on bather IE exposure vs incidence of gastro-enteritis. Simulated reduction in the risk of illness by reduced faecal loading was multiplied by a willingness to pay for risk reduction to estimate the annual benefits of mitigation. Health benefits of reducing loading by 75% at Irvine Beach were estimated by a willingness to pay method to be about pound 276k pa. Estimated annualised costs of diffuse pollution mitigation measures across the catchment were higher (> pound 1m), and it is very unlikely that 75% mitigation is achievable with current stocking rates. Further work should explore the influence of uncertainty of model parameters, and use emerging epidemiological information on specific zoonotic pathogens such as E. coli O157 and Cryptosporidium. Other components of the value of clean water should also be included to obtain a complete estimate of the cost:benefit of mitigation.     

Evaluation of the relationship between two different methods for enumeration fecal indicator bacteria： Colony-forming unit and most probable number

Most probable number (MPN) and colony-forming unit (CFU) estimates of fecal indicator bacteria (FIB) concentration are common measures of water quality in aquatic environments. Thus, FIB intensively monitored in Yeongsan Watershed in an attempt to compare two di erent methods and to develop a statistical model to convert from CFU to MPN estimates or vice versa. As a result, the significant di erence was found in the MPN and CFU estimates. The enumerated Escherichia coli concentrations in MPN are greater than those in CFU, except for the measurement in winter. Especially in fall, E. coli concentrations in MPN are one order of magnitude greater than that in CFU. Contrarily, enterococci bacteria in MPN are lower than those in CFU. However, in general, a strongly positive relationship are found between MPN and CFU estimates. Therefore, the statistical models were developed, and showed the reasonable converting FIB concentrations from CFU estimates to MPN estimates. We expect this study will provide preliminary information towards future research on whether di erent analysis methods may result in di erent water quality standard violation frequencies for the same water sample.     

南方某城市地表水体中粪源性污染指示微生物的分布特征研究

随着城市居民亲水娱乐活动日益增加,研究城市地表水体的粪源性微生物污染特征,开展人体健康风险评价,并以此为基础开展有效的水质监测和风险管理,对于人口密集的城市区域尤为重要.以我国南方某城市的5个典型地表水体为案例,监测总大肠菌（TC）、粪大肠菌（FC）、大肠埃希氏菌（EC）和肠球菌（ENT）这4种粪源性污染指示微生物以及常规理化水质指标,研究指示微生物在城市地表水体中的浓度水平、时间和空间分布特征以及不同水质指标之间的相关性.结果表明,案例水体中TC和FC通常在10^3～10^7个.L^-1,EC和ENT通常分别低于200个·L^-1和105个·L^-1;4种指示微生物的浓度分布呈现季节变化特征,并且能够指示水体受到周边环境的污染状况;4种指示微生物指标之间以及微生物指标与常规理化水质指标（如溶解氧等）之间具有一定的相关性.     

FECAL‐INDICATOR BACTERIA IN STREAMS ALONG A GRADIENT OF RESIDENTIAL DEVELOPMENT1

ABSTRACT: Fecal‐indicator bacteria were sampled at 14 stream sites in Anchorage, Alaska, USA, as part of a study to determine the effects of urbanization on water quality. Population density in the subbasins sampled ranged from zero to 1,750 persons per square kilometer. Higher concentrations of fecal‐coliform, E. coli, and enterococci bacteria were measured at the most urbanized sites. Although fecal‐indicator bacteria concentrations were higher in summer than in winter, seasonal differences in bacteria concentrations generally were not significant. Areas served by sewer systems had significantly higher fecal‐indicator bacteria concentrations than did areas served by septic systems. The areas served by sewer systems also had storm drains that discharged directly to the streams, whereas storm sewers were not present in the areas served by septic systems. Fecal‐indicator bacteria concentrations were highly variable over a two‐day period of stable streamflow, which may have implications for testing of compliance to water‐quality standards.     

A Regional Survey of the Microbiological Water Quality along the Shoreline of the Southern California Bight

A regional survey of the microbiological water quality along the shoreline of the Southern California Bight (SCB), from Point Conception south to Ensenada, Mexico, was conducted during August, 1998, by 36 agencies under the coordination of the Southern California Coastal Water Research Project (SCCWRP). Microbiological water quality was assessed by calculating the percentage of shoreline-mile-days that exceeded bacterial indicator thresholds for total and fecal coliforms, total/fecal ratios, and enterococci. Sample sites were selected using a stratified random sampling approach, with the SCB recreational shoreline divided into six strata: high- and low-use sandy beaches, high- and low-use rocky shoreline, and perennial and ephemeral freshwater outlets. Samples were collected on a weekly basis at a total of 253 sites, beginning on August 2^nd, 1998 and continuing for five weeks. Samples were analyzed by 22 participating labs using their normal methods (multiple tube fermentation, membrane filtration, Colilert® and/or Enterolert®). All labs met testing criteria established through intercalibration exercises and quality control check samples distributed during the sampling period. Nearly 95% of the shoreline-mile days did not exceed daily and monthly bacterial indicator thresholds, demonstrating good bacteriological water quality along the SCB shoreline. Freshwater outlets, comprised mainly of storm drains, had the poorest water quality with 60% and 40% of the shoreline-miles exceeding monthly and daily thresholds, respectively. Freshwater outlets were also more likely to demonstrate exceedances by multiple indicators at a single site, and repeat exceedances at sites over the five-week period. Compared with the southern California beaches, Mexican beaches had nearly 5 times the number of exceedances for total and fecal coliforms, and nearly 8 times the number of exceedances for total/fecal ratios.     

Antibacterial effects of Anodonta cygnea fluids on Escherichia coli and enterococci multi-drug-resistant strains: environmental implications

The persistence of bacteria in Anodonta cygnea largely depends on the hemolymph bactericidal activity against aquatic micro-organisms.

The aim of this study was to assess the in vitro bactericidal activity of whole hemolymph against multi-drug-resistant Escherichia coli and enterococci strains. Four mussels were injected with multi-resistant strains of E. coli in order to determine their in vivo bactericidal reactivity. In vitro experiments showed that the hemocytes viability decreased almost 70% in 4 h, the same happened in the control hemolymph. Enterococci tested in in vitro experiments were more susceptible than E. coli to whole hemolymph and hemocytes fractions. None of the enterococci bacteria was detected in the hemolymph fractions from 24 to 72 h, while E. coli was still detectable 72 h after inoculation both in the control and respective plasma fractions. The microbial inhibition on both hemolymph and cell pellets suggest that hemocytes may be the main responsibles for that process.

In vivo experiments showed that hemolymph inhibited the E. coli load injected and it was correlated with a high tendency for the increase in hemocytes counts, after 72 h. High adherence of E. coli and an intense pseudopods manifestation, mainly to the granulocytes, suggest a clear phagocytosis process.     

热水解污泥厌氧消化过程中肠球菌抗生素抗性基因与毒力基因的转归

城市污泥中含有大量肠球菌,可携带抗生素抗性基因(antibiotic resistance genes,ARGs)和毒力基因(virulence gene,VGs),从而具有潜在的耐药性和致病性,对人类健康存在巨大威胁.为此考察了热水解污泥在中温(40℃)/高温(55℃)厌氧消化过程中肠球菌的耐药表型、基因型及携带VGs的变化规律.结果表明,厌氧进泥中肠球菌对阿奇霉素的耐药率均显著高于螺旋霉素和四环素.高温厌氧对肠球菌的数量及耐药性具有更好地控制及削减效果.高温厌氧消化可能会促进四环素类抗性基因在肠球菌的表达.中温、高温厌氧消化可促进ARGs在肠球菌中发生水平转移,导致其潜在双重甚至多重耐药性增加.中温厌氧消化可降低肠球菌同时具有潜在致病性和耐药性的几率,而高温厌氧消化则会增加此风险.