Bacterial indicators of risk of diarrhoeal disease from drinking-water in the Philippines

Inadequate measures of water quality have been used in many studies of the health effects associated with water supplies in developing countries. The present 1-year epidemiological-microbiological study evaluated four bacterial indicators of tropical drinking-water quality (faecal coliforms, Escherichia coli, enterococci and faecal streptococci) and their relationship to the prevalence of diarrhoeal disease in a population of 690 under-2-year-olds in Cebu, Philippines. E. coli and enterococci were better predictors than faecal coliforms of the risk of waterborne diarrhoeal disease. Methods to enumerate E. coli and enterococci were less subject to interference from the thermotolerant, non-faecal organisms that are indigenous to tropical waters. Little difference was observed between the illness rates of children drinking good quality water (less than 1 E. coli per 100 ml) and those drinking moderately contaminated water (2-100 E. coli per 100 ml). Children drinking water with greater than 1000 E. coli per 100 ml had significantly higher rates of diarrhoeal disease than those drinking less contaminated water. This threshold effect suggests that in developing countries where the quality of drinking-water is good or moderate other transmission routes of diarrhoeal disease may be more important; however, grossly contaminated water is a major source of exposure to faecal contamination and diarrhoeal pathogens.     

Development of a process-based model to predict pathogen budgets for the Sydney drinking water catchment

In drinking water catchments, reduction of pathogen loads delivered to reservoirs is an important priority for the management of raw source water quality. To assist with the evaluation of management options, a process-based mathematical model (pathogen catchment budgets - PCB) is developed to predict Cryptosporidium, Giardia and E. coli loads generated within and exported from drinking water catchments. The model quantifies the key processes affecting the generation and transport of microorganisms from humans and animals using land use and flow data, and catchment specific information including point sources such as sewage treatment plants and on-site systems. The resultant pathogen catchment budgets (PCB) can be used to prioritize the implementation of control measures for the reduction of pathogen risks to drinking water. The model is applied in the Wingecarribee catchment and used to rank those sub-catchments that would contribute the highest pathogen loads in dry weather, and in intermediate and large wet weather events. A sensitivity analysis of the model identifies that pathogen excretion rates from animals and humans, and manure mobilization rates are significant factors determining the output of the model and thus warrant further investigation.     

Development of a process-based model to predict pathogen budgets for the Sydney drinking water catchment

In drinking water catchments, reduction of pathogen loads delivered to reservoirs is an important priority for the management of raw source water quality. To assist with the evaluation of management options, a process-based mathematical model (pathogen catchment budgets - PCB) is developed to predict Cryptosporidium, Giardia and E. coli loads generated within and exported from drinking water catchments. The model quantifies the key processes affecting the generation and transport of microorganisms from humans and animals using land use and flow data, and catchment specific information including point sources such as sewage treatment plants and on-site systems. The resultant pathogen catchment budgets (PCB) can be used to prioritize the implementation of control measures for the reduction of pathogen risks to drinking water. The model is applied in the Wingecarribee catchment and used to rank those sub-catchments that would contribute the highest pathogen loads in dry weather, and in intermediate and large wet weather events. A sensitivity analysis of the model identifies that pathogen excretion rates from animals and humans, and manure mobilization rates are significant factors determining the output of the model and thus warrant further investigation.     

邯郸市农村集中供水微生物污染状况调查

目的全面了解邯郸市农村集中供水微生物污染状况,为改善农村生活饮用水的卫生质量提供依据。方法分别在枯水期和丰水期对我市6个县的108个自然村集中式供水的水源水和末梢水进行监测,按GB/T5750-2006《生活饮用水标准检验方法》检测菌落总数、总大肠菌群、耐热大肠菌群、大肠埃希氏菌;依据GB5749-2006《生活饮用水卫生标准》进行评价。结果邯郸市农村集中式供水微生物指标总合格率48.38%,其中细菌总数合格率为最低为50.93%。结论邯郸市农村生活饮用水微生物污染严重,有导致肠道传染病暴发流行的安全隐患,望政府加大农村供水设施建设的投入和对农村饮水卫生的监管力度,以保障农村居民饮水安全。     

Microbial quality of water in rural communities of Trinidad.

A cross-sectional study was conducted in four rural communities of northeastern Trinidad to determine the microbial quality of water supply to households and that quality's relationship to source and storage device. Of the 167 household water samples tested, total coliforms were detected in 132 of the samples (79.0%), fecal coliforms in 102 (61.1%), and E. coli in 111 (66.5%). There were significant differences among the towns in the proportion of the samples contaminated with coliforms (P < 0.001) and E. coli (P < 0.001). Of 253 strains of E. coli studied, 4 (1.6%) were mucoid, 9 (3.6%) were hemolytic, and 37 (14.6%) were nonsorbitol fermenters. Of 69 isolates of E. coli tested, 10 (14.5%) were verocytotoxigenic. Twenty-eight (14.0%) of 200 E. coli isolates tested belonged to enteropathogenic serogroups. Standpipe, the most common water source, was utilized by 57 (34.1%) of the 167 households. Treated water (pipeborne in homes, standpipes, or truckborne) was supplied to 119 households (71.3%), while 48 households (28.7%) used water from untreated sources (rain, river/stream, or well) as their primary water supply. The type of household storage device was associated with coliform contamination. Water stored in drums, barrels, or buckets was more likely to harbor fecal coliforms (74.2% of samples) than was water stored in tanks (53.3% of samples), even after controlling for water source (P = 0.04). Compared with water from other sources, water piped into homes was significantly less likely to be contaminated with total coliforms (56.9% versus 88.8%, P < 0.001) and fecal coliforms (41.2% versus 69.8%, P < 0.01), even when the type of storage device was taken into account. However, fecal contamination was not associated with whether the water came from a treated or untreated source. We concluded that the drinking water in rural communities in Trinidad was grossly unfit for human consumption, due both to contamination of various water sources and during household water storage.     

不同饮水类型与结直肠癌发病率的流行病学研究

目的 探索不同饮水类型与结直肠癌发病率之间的关系。方法 随机抽取了浙江省海宁市的８个乡镇为研究区,应用回顾前瞻性研究方法,分别对不同饮水类型的结肠、直肠癌发病率进行分析并作相对危险度（ＲＲ）估计。结果 饮用井水、自来水、河水和池塘水者的结直肠癌发病率男性分别为３．１９／１０万、７．９９／１０万、４５．０６／１０万和１２６．０４／１０万;女性分别为３．０６／１０万、５．１７／１０万、６３．４３／１０     

秦皇岛经济技术开发区农村饮用水情况调查报告

目的:了解秦皇岛经济技术开发区农村饮用水卫生现状,为改善农村饮用水工作提供科学依据。方法:覆盖全区所有村镇,开展农村生活饮用水水源类型、供水方式、水源污染等情况以及生活饮用水水质监测等调查,依据《生活饮用水卫生标准》(GB5749-2006)对水质卫生质量进行评价。结果:秦皇岛经济技术开发区农村枯水、丰水期水质合格率分别为42.32%和21.45%,地面水、地下水水质合格率分别为30.56%和32.04%,以地下水为水源的深水井与浅水井水质合格率为39%和19.27%,集中式供水与分散式供水合格率为35%和31.23%。结论:秦皇岛经济技术开发区的农村改水工作应进一步完善,农村饮用水消毒工艺必不可少,今后应加大饮水卫生宣传力度及监督监测频率,以保证全区农村饮水的卫生和安全。     

河口县农村集中式供水水质检测结果分析

目的:了解河口县农村集中式供水的水质状况,为政府及相关部门对农村饮水工程的建设与管理提供科学依据。方法:对河口县46个自然村基本情况进行现场调查,并进行水质检测分析。结果:736份农村饮用水水样合格率仅为12.91%,丰水期水质与枯水期水质无显著性差异(P>0.05),出厂水与末梢水水质无显著性差异(P>0.05)。结论:河口县农村集中式供水水质卫生状况较差,受微生物污染非常严重,加强对农村饮水安全工程管理和饮水消毒刻不容缓。     

Microbial indicators and fresh water quality assessment

Traditionally, the microbiological quality of waters has been measured by the analysis of indicator microorganisms. The article reviews the sanitary significance of traditional indicators of faecal contamination (total coliforms, faecal coliforms and faecal streptococci) and points out their limits. For some characteristics Escherichia coli may be considered a more useful indicator then faecal coliforms and recently it has been included in all recent laws regarding fresh, marine and drinking water. A clearer taxonomic definition of faecal streptococci evidenced the difficulty into defining a specific standard methodology of enumeration and suggested the more suitable role of enterococci as indicator microorganisms. Several current laws require the detection of enterococci. The resistance of Clostridium perfringens spores may mean that they would serve as a useful indicator of the sanitary quality of sea sediments.     

Microbiological evaluation of water quality from urban watersheds for domestic water supply improvement

Agricultural and urban runoffs may be major sources of pollution of water bodies and major sources of bacteria affecting the quality of drinking water. Of the different pathways by which bacterial pathogens can enter drinking water, this one has received little attention to date; that is, because soils are often considered to be near perfect filters for the transport of bacterial pathogens through the subsoil to groundwater. The goals of this study were to determine the distribution, diversity, and antimicrobial resistance of pathogenic Escherichia coli isolates from low flowing river water and sediment with inputs from different sources before water is discharged into ground water and to compare microbial contamination in water and sediment at different sampling sites. Water and sediment samples were collected from 19 locations throughout the watershed for the isolation of pathogenic E. coli. Heterotrophic plate counts and E. coli were also determined after running tertiary treated water through two tanks containing aquifer sand material. Presumptive pathogenic E. coli isolates were obtained and characterized for virulent factors and antimicrobial resistance. None of the isolates was confirmed as Shiga toxin E. coli (STEC), but as others, such as enterotoxigenic E. coli (ETEC). Pulsed field gel electrophoresis (PFGE) was used to show the diversity E. coli populations from different sources throughout the watershed. Seventy six percent of the isolates from urban sources exhibited resistance to more than one antimicrobial agent. A subsequent filtration experiment after water has gone through filtration tanks containing aquifer sand material showed that there was a 1 to 2 log reduction in E. coli in aquifer sand tank. Our data showed multiple strains of E. coli without virulence attributes, but with high distribution of resistant phenotypes. Therefore, the occurrence of E. coli with multiple resistances in the environment is a matter of great concern due to possible transfer of resistant genes from nonpathogenic to pathogenic strains that may result in increased duration and severity of morbidity.     

2008年兰州市农村集中式供水现状调查研究

目的了解兰州市农村集中式供水现状,为兰州市进一步进行农村改水工作,制定农村饮水安全工程规划,保障农民身体健康提供科学依据。方法对兰州市38个农村集中式供水点基本情况进行现场调查,并进行水质抽样检测。调查的数据全部输入Excel数据库,率的比较采用SPSS13.0软件进行χ2检验,P<0.05为差异有统计学意义。结果本调查研究的38个供水点中79.0%的供水点未进行水处理,84.2%无任何消毒设备,未进行任何方式消毒;水质合格率为20.4%,以细菌学指标超标最为严重,菌落总数超标率高达65.8%;丰水期水质明显差于枯水期(P<0.05)。结论兰州市农村集中式供水水质卫生状况相当差,应加强农民群众饮水卫生知识的教育,保护水源不受污染,同时加强饮水的净化和消毒,加强水质监测。     

丹阳市生活饮用水卫生学调查

对丹阳市２７个乡镇生活饮用水调查结果表明：丹阳市生活饮用水水源主要是浅井水、河水和沟塘水；无论是集中式供水或分散式供水，９０％以上的水源有生活污染源；各指标的超标率以氨氮居首位，其次是耗氧量、浑浊度；丹阳市生活饮用水的有机污染严重，生活饮用水水源的水质最差的是沟塘水，其次是河水，浅井水的水质较好；丹阳市饮用不合格水的人口数占４０．９％。     

Microbiological standards for water and their relationship to health risk

Maintenance of the microbiological quality of water has been used as an important means of preventing waterborne disease throughout the twentieth century. The commonest microbiological tests done on water are for coliforms and Escherichia coli (or faecal coliform). This paper reviews the legislative and other guidance for microbial standards in drinking and bathing waters and considers evidence for the relationship between the microbiological quality of water and risk to human health. In the past measures of the microbiological quality of water correlated well with risks of acquiring gastrointestinal disease. More recent work suggests that gastrointestinal disease is more strongly associated with the presence of enterococci than of E. coli. New diseases such as cryptosporidiosis have been shown to cause outbreaks of waterborne disease when levels of conventional microbiological parameters are satisfactory. In response to this, and because of failure of prosecution in one outbreak, the United Kingdom (UK) Government has introduced new legislation that requires water providers to perform a risk assessment on their water treatment facilities and to implement continuous monitoring for cryptosporidium. A new European directive on drinking water has been introduced and legislation on cryptosporidium in drinking water has been proposed in the UK.     

Child dysentery in the Limpopo Valley: a cohort study of water, sanitation and hygiene risk factors

The objective of this cohort study was to assess risk factors for child dysentery and watery diarrhoea. The study participants consisted of 254 children aged 12–24 months in rural South Africa and Zimbabwe in households where drinking water was collected from communal sources. The main outcome measure was the most severe diarrhoea episode: dysentery, watery diarrhoea or none. For dysentery, drinking water from sources other than standpipes had a relative risk ratio of 3.8 (95% CI 1.5–9.8). Poor source water quality, as indicated by Escherichia coli counts of 10 or more cfu 100 ml^-1, increased risk by 2.9 (1.5–5.7). There were no other significant risk factors for dysentery and none for watery diarrhoea. In this study, endemic dysentery is associated only with faecal contamination of source water. Sources other than standpipes, including improved groundwater, are of greater risk. Remediation of water quality by treatment at source or in the household will be required to achieve access to safe drinking water in accordance with the 7th Millennium Development Goal.     

Bottled water: United States consumers and their perceptions of water quality

Consumption of bottled water is increasing worldwide. Prior research shows many consumers believe bottled water is convenient and has better taste than tap water, despite reports of a number of water quality incidents with bottled water. The authors explore the demographic and social factors associated with bottled water users in the U.S. and the relationship between bottled water use and perceptions of the quality of local water supply. They find that U.S. consumers are more likely to report bottled water as their primary drinking water source when they perceive that drinking water is not safe. Furthermore, those who give lower ratings to the quality of their ground water are more likely to regularly purchase bottle water for drinking and use bottle water as their primary drinking water source.     

Problems of epidemic safety of drinking water use by the population of Russia

Quantitative relationships were studied between the indicators (common coliform bacteria (CCP), glucose-positive bacteria (GPB), thermoduric bacteria (TDB), coliform bacteria, enterococci, clostridia, coliphages) and the opportunistic (Pseudomonas aeruginosa, Proteus, Klebsiella) and pathogenetic (Salmonella and intestinal viruses) microorganisms at the stages of effluent purification and decontamination, in processes of self-purification in the water reservoirs and of water preparation at water-supplying stations, as well as in the association with the incidence of acute intestinal infections of bacterial and viral genesis in different climatic zones of the country. Salmonella and the opportunistic bacteria of the Enterobacteriaceae family and Pseudomonas aeruginosa were found to be highly resistant to detoxifying agents and environmental factors, adaptable, able to reproduce in pure water, to long survive in underground waters, and to accumulate when water is desalinated at the erections. The cases of intestinal infections were found in the population using the portable water of the standard quality in terms of E. coli, TDB, CCB, and enterococci. In this case only the wider integral index of GPB, which includes the indices of E. coli, TDB, CCB, as well as lactose-negative pathogenic and opportunistic species retains its sanitary significance in terms of all signs and is a reliable indicator of the potential epidemic hazard of drinking water use. Long-term studies have provided evidence for the sanitary value of coliphages as indicators of viral drinking water contamination.     

Estimation of pathogen concentrations in a drinking water source using hydrodynamic modelling and microbial source tracking

The faecal contamination of drinking water sources can lead to waterborne disease outbreaks. To estimate a potential risk for waterborne infections caused by faecal contamination of drinking water sources, knowledge of the pathogen concentrations in raw water is required. We suggest a novel approach to estimate pathogen concentrations in a drinking water source by using microbial source tracking data and fate and transport modelling. First, the pathogen (norovirus, Cryptosporidium, Escherichia coli O157/H7) concentrations in faecal contamination sources around the drinking water source Lake R?dasj?n in Sweden were estimated for endemic and epidemic conditions using measured concentrations of faecal indicators (E. coli and Bacteroidales genetic markers). Afterwards, the fate and transport of pathogens within the lake were simulated using a three-dimensional coupled hydrodynamic and microbiological model. This approach provided information on the contribution from different contamination sources to the pathogen concentrations at the water intake of a drinking water treatment plant. This approach addresses the limitations of monitoring and provides data for quantitative microbial risk assessment (QMRA) and risk management in the context of faecal contamination of surface drinking water sources.     

Epidemiological study on contamination of water and diarrheal diseases in a rural community in northeast Thailand

An epidemiological and bacteriological study of diarrheal diseases as well as the relation between domestic-use water and passage of enteric pathogens with stools of the villagers was performed in the northeastern rural area of Thailand on 4 different occasions during the 3 years from 1992-1994. The questionnaire study indicated that 93% of the residents used rain water stored in containers for drinking and other domestic uses, and that 28% of them filtrated and/or boiled the water before drinking it. About 90% of drinking water samples collected from the same residents showed positive responses for the preliminary test ofEscherichia coli contamination. Furthermore, a precise bacteriological survey indicated that more than half of the drinking water samples collected from containers storing rain water were contaminated with various enteropathogenic bacteria, includingE. coli, Vibrio spp. andShigella spp. The new serotype ofV. cholerae O139, synonym 'Bengal cholerae,' which could be isolated from different specimens, is replacing the traditional species ofVibrio. Forty-one per cent of the villagers carried enteropathogenic bacteria in their stools. Most of them were asymptomatic carriers and only a few of them showed clinical features of diarrhea. A few concrete propositions were discussed to supply safe water in these areas where drinkable underground water is not available.     

2011年大连市农村生活饮用水水质卫生监测结果分析

目的了解农村生活饮用水水质卫生状况,为今后改善农村饮用水卫生状况和保障农村居民生活饮用水安全提供科学依据。方法2011年3—8月随机选择大连市250处农村集中式供水工程进行基本情况调查,对每处出厂水和末梢水进行采样检测。结果本市供水方式以分散式供水为主,农村集中式供水以地下水为主,完全处理的工程占2．09％。抽检1000份水样,在不计算消毒指标的情况下,总合格率为73．80％,枯水期和丰水期水质合格率分别为80．80％和66．80％,出厂水和末梢水水质合格率分别为75．00％和72．60％。微生物和硝酸盐超标较严重,其中总大肠菌群、菌落总数、硝酸盐、耐热大肠菌群合格率分别为93．20％、91．40％、83．70％、75．00％。结论大连农村集中水供水工程水消毒处理设施不完善,水质合格率低,微生物指标和硝酸盐超标率高,饮用水安全存在一定的隐患。