Numbers Of Indicator Bacteria Research Articles

RESEARCH OF METHODS FOR WATER DISINFECTION

Access to safe water remains a challenge in conflict-affected areas. Irregular water supply, which is becoming a common phenomenon, is caused by numerous factors, in particular: 1) wear and tear of water mains that need repair and were damaged as a result of hostilities; 2) reduction in the efficiency of important pumps due to power outages, shelling of power lines that supply energy to the pumps; 3) access problems due to the presence of armed groups, the presence of mines or unexploded shells, as well as the poor condition of roads, which prevent local residents from reaching wells or obtaining water delivered by tankers; 4) problems with access, due to which workers cannot perform repair work or obtain spare parts necessary for repairing water pipes; 5) normative legal acts that limit the freedom of movement and/or supply of goods or water across the contact line, affecting the supply of water from settlements controlled by Ukraine to settlements not controlled by Ukraine; as well as 6) frequent water supply interruptions, which contributed to the deterioration of the situation. In most cases, the use of a combined system can be optimal for high-quality water disinfection. Combined water disinfection is carried out by physical and chemical methods at the same time. Water pollution is determined by its bacteriological examination, which shows the total number of bacteria and the number of indicator bacteria of the coliform group (E. coli) in 1 milligram of water. The main type of bacteria of the Escherichia coli group is E.coli bacteria, which in practice are the easiest to determine and have a high level of resistance coefficient. Traditional methods of water disinfection, namely chlorination and ozonation, are harmful byproducts of disinfection. Ultraviolet radiation is a safe alternative, but quite energy-consuming. The paper analyzes existing methods of decontamination of drinking water, examines the state of the issue, and analyzes alternative methods of decontamination of drinking water.

Monitoring faecal contamination and relationship of physicochemical variables with faecal indicator bacteria numbers in Bukavu surface waters, tributaries of Lake Kivu in Democratic Republic of Congo

The faecal indicator bacteria (FIB) in association with physicochemical parameters were monitored twice a month from 2017 to 2019 in the Kahuwa (KW), Wesha (WS), Tshula (TL), Bwindi (BN), and Nyamuhiga (NG) rivers and their tributaries. Results showed severe faecal contamination of waters compared to the WHO standards, and the FIB load levels (Mesophilic aerobic bacteria (MAB), Total coliforms (TC), Faecal coliforms (FC), and Faecal streptococci (FS)) were varied between stations (Kruskal-Wallis test (K) = 703; p < 0.01) and seasons (Fisher's test (F) = 2.13; p < 0.01). However, the presence of pathogenic bacteria such as Escherichia coli, Salmonella typhi, Streptococcus sp., Shigella dysenteriae, Aeromonas sp., Vibrio cholerae, and other bacteria indicative of faecal contamination were reported. Water temperature (WT) and dissolved oxygen (DO) were within the WHO standards for surface waters, except pH for some stations on KW and NG rivers, where it was highly alkaline. The highest nutrients concentrations (PO43–, NH4+, NO2– and NO3–) were recorded in the dry season for all stations, except in KW and NG rivers from the midstream to downstream stations. The structural equations regression model (F test, p ≤ 0.05 with R2) indicated a significant (p ≤ 0.05) positive correlation between the value of physicochemical parameters (WT, pH, PO43–, NH4+, NO2– and NO3–) and that of detected FIB numbers, except for DO which negatively affects bacteria numbers. The FC/FS ratio (1.01 – 4.30) linked polluted waters to human sources while the COD/BOD5 ratio (1.90 – 2.39) categorized them under domestic origin wastewater. The current degradation status of these rivers require a rapid waste management strategy and an efficient sanitation plan development along each catchment. Installation of wastewater treatment plants (WWTPs) with biological treatment can mitigate the ecological and health risks of the rivers and the coastal zone of Lake Kivu.

Biostimulating Effects of Disintegrated Waste Activated Sludge on Soil Enzyme Activities

Sludge disintegration methods are used in a variety of applications to enhance sludge characteristics or bring about a reduction in solid content of sludge. Hydrodynamic cavitation is one of the mechanical disintegration methods used on waste-activated sludge, and its efficiency has been investigated in recent years. In this study, the possible use of waste-activated sludge disintegrated by hydrodynamic cavitation and chemically assisted hydrodynamic cavitation as a soil amendment was evaluated by an incubation procedure. Possible biostimulating effects were assessed by monitoring the variations in soil enzyme activities. The obtained results indicated that sludge solubilization was effectively performed with respect to soluble chemical oxygen demand, soluble total Kjeldahl nitrogen and soluble total phosphorus. According to the incubation study, the biostimulating/bioremediating properties of waste-activated sludge were significantly improved by the applied methods. Especially after a 60-day incubation period, the levels of urease, alkaline phosphatase, β-glucosidase and dehydrogenase activities in soils applied with a high dose of disintegrated sludge were significantly higher than the levels in raw sludge-amended soils. Consequently, it is thought that mechanically and chemically disintegrated waste-activated sludge with reduced numbers of indicator bacteria can be considered as a way of soil amendment to rehabilitate the quality of environmentally stressed soils.

Evaluation of the effectiveness of disinfection in dog shelter

Cleaning and disinfection are among the most important tasks in shelters and an important link in the prevention and battle against infectious diseases. Inadequate cleaning and ineffective disinfection can spread the disease to animals in the surrounding pens or to people during their daily contact and care of the animals. It is important to follow the order of the individual steps performed during hygiene procedures and carry out subsequent control of their efficacy. The aim of this study was to evaluate the effectiveness of disinfection by means of swabs taken from selected surfaces in a dog shelter – Happy dog, located in eastern Slovakia. The surfaces were disinfected with Savo Prim contains active substance sodium hypochlorite and anionic surfactant. For good cleaning effect was added disinfectant in a ratio of 1:5 to hot water at a temperature of 50°C and sprayed under pressure of 50 Bar. The effectiveness of mechanical cleaning followed by disinfection was evaluated by microbiological swabs from watering and food bowls, wall and floor. Swabs were taken before and after mechanical cleaning and disinfection, from 10cm2 areas. The surface area was wiped with a sterile cotton swab, the swab was placed in a sterile tube with 10ml of sterile saline solution and 0.1ml from this mixture was applied to Endo agar and meat peptone agar. Swabbing of the disinfected surfaces showed a significant decrease in TCB (total count of bacteria) and CB (coliform bacteria). However, on the walls and floors were detected small count of TCB and CB after disinfection in comparison with the counts detected before cleaning but the number of indicator bacteria was below the recommended value. Based on these observations, we can evaluate the hygienic program with the disinfection performed in the shelter as sufficient.

Proof of Concept for Ozone-Based Disinfection of Heater Cooler Units

Abstract Heater Cooler Units (HCUs) are frequently used not only during heart surgery but also in ECMO therapy to regulate the blood temperature of patients. It is known from cardiac surgery that the water circuits of HCUs can be bacterially contaminated and under adverse conditions can lead to a nosocomial infection of the patient. The addition of chemical disinfectants to the water of HCUs is problematic. In addition, it is an increasingly significant cost factor due to the required material and personnel input. The aim of this research project is both the development of an automated device for disinfecting water in HCUs and proof of its effectiveness. The device is based on ozone, a substance with known antimicrobial properties. To prevent ozone from coming into contact with the HCU components, the water is irradiated with UV light (254nm). Two bypasses and ozone sensors guarantee a complete elimination of residual ozone. The effectiveness of the device was tested by series of experiments with the surrogate germ, Pseudomonas aeruginosa. The device allows a wide range of ozone concentrations and exposure times to be selected. In previous test series, it has been shown both that a reduction of the bacterial count to drinking water quality can be achieved with a treatment time of only one hour, and that self-cleaning can be carried out effectively before clinical use, and in standby mode. Attention must be paid to the water quality in HCUs as a potential source of infection, regardless of where they are used. The "proof of concept" showed an excellent disinfection effect with simultaneous elimination of excess ozone to drinking water levels. The number of indicator bacteria in the water tank of the dummy HCU was reduced by approx. 98% after only 30 minutes.

건고추 생산 농장의 위생지표세균과 병원성미생물 오염도 조사

The purpose of this study was to investigate the main source of contamination of dried red pepper by assessing microbial loads on red peppers, washing water, washing machines, harvesting containers, and worker gloves that had come in contact with the dried red pepper. To estimate microbial loads, indicator bacteria (total bacteria, coliform bacteria and Escherichia coli) and pathogenic bacteria (E. coli O157:H7, Salmonella spp., Listeria monocytogenes, and Clostridium perfringens) were enumerated. The results showed that the numbers of indicator bacteria increased significantly after washing red peppers compared with that before washing (p&lt;0.05). Moreover, E. coli and Listeria spp. were recovered from the red peppers after washing and from the ground water used in the washing process. The number of indicator bacteria on red peppers dried in the green house was lower than that on red peppers dried in a dry oven (p&lt;0.05). However, E. coli O157:H7, Salmonella spp., L. monocytogenes, and C. perfringens were not detected. These results suggested that a disinfection technique may be needed during the washing step in order to prevent potential contamination. In addition, hygienic practices during the drying step using the dry oven, such as establishment of an optimal temperature, should be developed to enhance the safety of dried red pepper.

Disinfection of rainwater as a way to their microbiological stability and safe use

Research on the microbiological quality of rainwater collected from roof surfaces indicates their significant contamination with microorganisms, including potentially pathogenic ones. The aim of the research was to attempt disinfection of rainwater with chemical methods and to evaluate the effectiveness of this disinfection. The research was carried out with the use of appropriate means in the case of decontamination of large volumes of water, when it is important to maintain their biological stability - chlorination and ozonation. After the disinfector was administered for 4 weeks, bacterial microflora (stability) was observed in stored water. The control was carried out by determining the total amount of bacteria at 37°C and the total amount of bacteria at 22°C on the reference medium (agar A) and on the non-standard substrate (R2A agar). The number of indicator bacteria was also determined: fecal streptococci and Escherichia coli (on the chromogenic medium). Changes in the amount of microorganisms after disinfection processes were also monitored by flow cytometry. The research results clearly indicate better chlorinating disinfection effects. It allows the removal of indicator microorganisms in a relatively short time (1 hour), and the effect of the disinfectant lasts up to about a half month.

Modular development of an inline monitoring system for waterborne pathogens in raw and drinking water

The state-of-the-art monitoring of drinking water hygiene is based on the cultivation and enumeration of indicator bacteria. Despite its proven reliability, this approach has the disadvantages of being (a) relatively slow and (b) limited to a small number of indicator bacteria. Ideally, alternative methods would be less time-consuming while providing information about a larger set of hygienically relevant microorganisms including viruses. In this paper, we present insights into the design of a modular concentration and detection system for bacteria, bacteriophages and viruses. Following further validation, this or similar techniques have the potential to extend and speed up the monitoring of raw and drinking water hygiene in the future. The system consists of different modules for the concentration of microorganisms, an amplification and detection unit that includes a module for the differentiation between live and dead microorganisms, and an automated system for decision support and self-diagnosis. The ongoing testing under controlled laboratory conditions and real-life conditions in the water supply industry yields further system improvements. Moreover, the increased sensitivity and broader range of microbiological parameters emphasize the need for a reconsideration of the currently used criteria for the assessment of (drinking) water hygiene.

The assessment of airborne bacterial and fungal contamination emitted by a municipal landfill site in Northern Poland

Airborne bacteria and fungi are important biological components of bioaerosol and play an important role in the conservation environmental. A microbiological study on bioaerosoles was carried out at the Municipal Waste Utilization Plant in Northern Poland and at points located beyond the facility at the distance of 150, 450, 1000 and 1250 m. The highest emission of bioaerosol occurred in the area of the waste landfill site and during compost pile turning. The total number of mesophilic bacteria, filamentous fungi and actinomycetes reached the values up to 104 CFU/m3. Strong air contamination with mannitol-positive and mannitol-negative staphylococci occurred remarkably more frequently in the area of the test facility than in the points beyond it. The number of indicator bacteria of Pseudomonas fluorescens was quite changeable and did not depend on a distance from pollutant emission source. The number of Escherichia coli rods remained at the low level of about 102 CFU/m3, and they were only isolated sporadically in the points beyond the landfill. The highest percentage of bacterial aerosol comprised Gram-positive cocci, and then Gram-positive bacilli. Mycological analyses confirmed the presence in the studied air of fungi with potentially allergic and mycotoxinogenic properties, such as: Aspergillus fumigatus, A. niger, A. terreus, Cladosporium herbarum and the genus Fusarium. The concentration level of microbial bioaerosol several times exceeded the threshold values recommended by the Polish Standards. The factors influenced the concentration of microorganisms in the tested air included the distance of the active landfill, weather conditions and the season.

Microbiological Evaluation of Pork and Chicken By-Products in South Korea

In this study, we aimed to evaluate the microbiological risk of pork and chicken by-products by enumerating indicator bacteria (total aerobic bacteria, coliforms, and Escherichia coli) and identifying pathogens such as Campylobacter and Salmonella. The antibiotic resistance of pathogenic isolates was determined, and molecular subtyping was performed using automated repetitive sequence-based PCR (rep-PCR). Pork and chicken by-products were collected from 10 processing plants. The mean numbers of total aerobic bacteria, coliforms, and E. coli from 95 pork by-product samples and 64 chicken by-product samples were 5.1, 3.6, and 2.4 log CFU/g and 4.5, 3.0, and 1.8 log CFU/g, respectively. The numbers of indicator bacteria in the gastrointestinal tract (small intestine, large intestine, and gizzard) were significantly higher than those in other organs. Salmonella and Campylobacter species were detected in 3 and 5 of 95 pork by-product samples and in 6 and 3 of 64 chicken by-product samples, respectively. Four of 9 Salmonella isolates examined were resistant to eight antibiotics, and each of these resistant strains produced an extended-spectrum β-lactamase. Most Campylobacter isolates were resistant to tetracycline (7 of 8 strains) and quinolones (7 of 8 strains). The similarity in rep-PCR patterns among Salmonella isolates was more closely associated with serotype than with the processing plant and type of meat. Conversely, the rep-PCR patterns of Campylobacter isolates were specific to the processing plant. Our findings could help agencies develop regulations for protection from foodborne bacterial infections arising from animal by-products.

Seasonal variability of faecal indicator bacteria numbers and die-off rates in the Red River basin, North Viet Nam.

The Red River is the second largest river in Viet Nam and constitutes the main water source for a large percentage of the population of North Viet Nam. Here we present the results of an annual survey of Escherichia coli (EC) and Total Coliforms (TC) in the Red River basin, North Viet Nam. The objective of this work was to obtain information on faecal indicator bacteria (FIB) numbers over an annual cycle and, secondly, to determine the die-off rates of these bacterial indicators. Monthly observations at 10 stations from July 2013–June 2014 showed that TC and EC reached as high as 39100 cfu (colony forming units) 100 ml−1 and 15300 colonies 100 ml−1, respectively. We observed a significant seasonal difference for TC (p < 0.05) with numbers being higher during the wet season. In contrast, no significant seasonal difference was found for EC. The FIB die-off rates ranged from 0.01 d−1 to a maximum of 1.13 d−1 for EC and from 0.17 d−1 to 1.33 d−1 for TC. Die-off rates were significantly higher for free bacteria than for total (free + particle attached) bacteria, suggesting that particle attachment provided a certain level of protection to FIB in this system.

Efficiency of biological treatment for the removal of total and thermotolerant coliform bacteria from domestic sewage

Researchers around the world have focused their efforts on devising combinations of technologies that are not only economically feasible but also effective in mitigating the impacts caused by wastes containing pathogens that pose potential risks to human and animal health. The purpose of this study was to evaluate the performance of a biological treatment system for removing total and thermotolerant coliform bacteria with a view to the possible organic recycling of domestic sewage. To this end, a tubular continuous flow anaerobic digester, with hydraulic retention time (HRT) of 25 days and an optional stabilization pond, were used to treat the sewage produced by 150 people in the municipality of Sertaozinho, SP, Brazil. The samples were collected weekly, always on the same day, at three different sampling points (inlet of the treatment system, the outlet of tubular digester, and the optional stabilization pond), totaling 108 samples. The MPN method was employed to determine the total coliform and thermotolerant coliform populations, using multiple series of three tubes (APHA, 2005). The system proved efficient in reducing the number of indicator bacteria of fecal contamination, showing a removal efficiency of 98.76% for total coliforms and of 99.29% for thermotolerant coliforms. However, a third treatment step involving polishing should be included to render the effluent suitable for use in fertigation or discharge into water bodies.

Rainfall intensity effects on removal of fecal indicator bacteria from solid dairy manure applied over grass-covered soil

The rainfall-induced release of pathogens and microbial indicators from land-applied manure and their subsequent removal with runoff and infiltration precedes the impairment of surface and groundwater resources. It has been assumed that rainfall intensity and changes in intensity during rainfall do not affect microbial removal when expressed as a function of rainfall depth. The objective of this work was to test this assumption by measuring the removal of Escherichia coli, enterococci, total coliforms, and chloride ion from dairy manure applied in soil boxes containing fescue, under 3, 6, and 9cmh−1 of rainfall. Runoff and leachate were collected at increasing time intervals during rainfall, and post-rainfall soil samples were taken at 0, 2, 5, and 10cm depths. Three kinetic-based models were fitted to the data on manure-constituent removal with runoff. Rainfall intensity appeared to have positive effects on rainwater partitioning to runoff, and removal with this effluent type occurred in two stages. While rainfall intensity generally did not impact the parameters of runoff-removal models, it had significant, inverse effects on the numbers of bacteria remaining in soil after rainfall. As rainfall intensity and soil profile depth increased, the numbers of indicator bacteria tended to decrease. The cumulative removal of E. coli from manure exceeded that of enterococci, especially in the form of removal with infiltration. This work may be used to improve the parameterization of models for bacteria removal with runoff and to advance estimations of depths of bacteria removal with infiltration, both of which are critical to risk assessment of microbial fate and transport in the environment.

Homogeneous Distribution of &amp;lt;i&amp;gt;Escherichia coli&amp;lt;/i&amp;gt; Measured within the Vertical Water Column of Small, Freshwater Streams

Sampling for coliform bacterial indicators such as Escherichia coli (E. coli) provides a universally accepted gauge of the microbiologic quality of fresh surface waters worldwide. Protocols for the capture, preservation, and analysis of indicator bacteria collected from moving waters (e.g., rivers, streams, canals, etc.) parallel those for collecting bacteria from standing waters (e.g., ponds, lakes, and impoundments). Strict depth- and width-integrated rules established for testing moving waters are likely a result of the historical precedence of our knowledge of bacterial stratification in standing waters. Sampling protocols for indicator bacteria in freshwater streams recommend capture and retrieval of samples from the mid-water column directed into the current and within the deepest portion of the channel to prevent collection of either benthic particles or surface films. Chi-square analyses of multiple stratified samples captured on the same date and time reveal that variability in sampling position at specified depths within the main stream column or within randomly chosen locations within the main stream channel has no effect (p ≥ 0.25) upon such indicator bacteria numbers. Additionally, these data are the first to show that concentrations of the common bacterial indicator, E. coli, are homogeneously distributed throughout both lateral area and vertical water column within/near a single sampling location of a moving water body up to 245 cubic feet per second (cfs) discharge. Moreover, one data point (bacterial sample) appears to represent the overall bacterial concentration of a small freshwater stream obtained from any single sampling location within/near the main channel for a given date and time. These findings suggest some latitude in sampling strategies for assessing small freshwater streams for indicator bacteria such as E. coli for workers in both environmental and public health fields.

Opportunistic pathogens in roof-captured rainwater samples, determined using quantitative PCR

In this study, quantitative PCR (qPCR) was used for the detection of four opportunistic bacterial pathogens in water samples collected from 72 rainwater tanks in Southeast Queensland, Australia. Tank water samples were also tested for fecal indicator bacteria (Escherichia coli and Enterococcus spp.) using culture-based methods. Among the 72 tank water samples tested, 74% and 94% samples contained E. coli and Enterococcus spp., respectively, and the numbers of E. coli and Enterococcus spp. in tank water samples ranged from 0.3 to 3.7 log10 colony forming units (CFU) per 100 mL of water. In all, 29%, 15%, 13%, and 6% of tank water samples contained Aeromonas hydrophila, Staphylococcus aureus, Pseudomonas aeruginosa and Legionella pneumophila, respectively. The genomic units (GU) of opportunistic pathogens in tank water samples ranged from 1.5 to 4.6 log10 GU per 100 mL of water. A significant correlation was found between E. coli and Enterococcus spp. numbers in pooled tank water samples data (Spearman's rs = 0.50; P < 0.001). In contrast, fecal indicator bacteria numbers did not correlate with the presence/absence of opportunistic pathogens tested in this study. Based on the results of this study, it would be prudent, to undertake a Quantitative Microbial Risk Assessment (QMRA) analysis of opportunistic pathogens to determine associated health risks for potable and nonpotable uses of tank water.

Molecular Approach to Microbiological Examination of Water Quality in the Grand Bay National Estuarine Research Reserve (NERR) in Mississippi, USA

Grand Bay National Estuarine Research Reserve (NERR) is an important ecosystem in the Mississippi Gulf Coast. It serves as important nursery areas for juveniles of many species of fish. The bay is also used for fishing, crabbing, oyster togging, boating as well as recreation. Like in other aquatic environments, this bay may be contaminated by microorganisms including pathogenic bacteria. The objective of this study was to evaluate the microbiological quality of water in the Grand Bay NERR and determine the levels and potential source(s) of human fecal pollution. To achieve this goal, water samples were collected aseptically every month in Bayou Heron, Bayou Cumbest, Point Aux Chenes Bay and Bangs Lake. Enterococci were concentrated from water samples by membrane filtration according to the methodology outlined in USEPA Method 1600. After incubation, DNA was extracted from bacteria colonies on the membrane filters by using QIAamp DNA extraction kit. Water samples were also tested for the presence of traditional indicator bacteria including: heterotrophic plate count, total coliforms, fecal coliforms, and Enterococcus bacteria. The marker esp gene was detected in one site of Bayou Cumbest, an area where human populations reside. Data from this study indicates higher concentrations of indicator bacteria compared to the recommended acceptable levels. Presence of esp marker and high numbers of indicator bacteria suggest a public health concern for shellfish and water contact activities. Hence, control strategies should be developed and implemented to prevent further contamination of the Grand bay NERR waters.

Prevalence of Vibrio parahaemolyticus in oyster and clam culturing environments in Taiwan

Vibrio parahaemolyticus is the most prevalent gastroenteritis pathogen in Taiwan and some other Asian countries, and it frequently occurs in oysters and other seafood. This study monitors changes in the density of V. parahaemolyticus and environmental parameters in oyster and hard clam aquacultural environments in Taiwan. Water, sediment and shellfish samples were collected from five sampling sites in 2008–2010, and analyzed for environmental physiochemical parameters, numbers of indicator bacteria (total aerobic counts, total coliforms and fecal coliforms), Vibrio and V. parahaemolyticus present. The results for open oyster farms and hard clam ponds did not differ significantly. V. parahaemolyticus was detected in 77.5, 77.5, 70.8 and 68.8% of the water, sediment, oyster and clam samples, respectively. The densities of V. parahaemolyticus were significantly higher in shellfish than in sediment or water samples, with mean values of 1.33, 1.04 and −0.02 Log CFU/g, respectively. Among these five sampling sites, Shengang and Fangyuan yielded significantly different data from those obtained at the other three sites. As determined by linear multiple regression, V. parahaemolyticus density in water samples depended significantly on the precipitation and Vibrio count, while the V. parahaemolyticus density in the sediment or shellfish samples depended significantly on the salinity of the seawater. Among 1076 isolates examined, a total of three putative pathogenic isolates were identified from 2.5% of the examined samples, and these isolates exhibited hemolytic or urease activities and the presence of gene markers for tdh, trh, type III secretion system (T3SS) 1 (vcrD1) or T3SS2α (vcrD2). The results herein may facilitate the assessment of risk associated with this pathogen in Taiwan and other geographically similar regions.

Terrestrial Sources Homogenize Bacterial Water Quality During Rainfall in Two Urbanized Watersheds in Santa Barbara, CA

Microbiological contamination from runoff is a human health concern in urbanized coastal environments, but the contamination sources are often unknown. This study quantified fecal indicator bacteria and compared the distributions of human-specific genetic markers and bacterial community composition during dry and wet weather in urban creeks draining two neighboring watersheds in Santa Barbara, CA. In a prior study conducted during exclusively dry weather, the creeks were contaminated with human waste as indicated by elevated numbers of the human-specific Bacteroidales marker HF183 (Sercu et al. in Environ Sci Technol 43:293-298, 2009). During the storm, fecal indicator bacterial numbers and loads increased orders of magnitude above dry weather conditions. Moreover, bacterial community composition drastically changed during rainfall and differed from dry weather flow by (1) increased bacterial diversity, (2) reduced spatial heterogeneity within and between watersheds, and (3) clone library sequences more related to terrestrial than freshwater taxa. Finally, the spatial patterns of human-associated genetic markers (HF183 and Methanobrevibacter smithii nifH gene) changed during wet weather, and the contribution of surface soils to M. smithii nifH gene detection was suspected. The increased fecal indicator bacteria numbers during wet weather were likely associated with terrestrial sources, instead of human waste sources that dominated during dry weather flow.

Resuscitation and quantification of stressed Escherichia coli K12 NCTC8797 in water samples

The aim of this study was to investigate the impact on numbers of using different media for the enumeration of Escherichia coli subjected to stress, and to evaluate the use of different resuscitation methods on bacterial numbers. E. coli was subjected to heat stress by exposure to 55 degrees C for 1h or to light-induced oxidative stress by exposure to artificial light for up to 8h in the presence of methylene blue. In both cases, the bacterial counts on selective media were below the limits of detection whereas on non-selective media colonies were still produced. After resuscitation in non-selective media, using a multi-well MPN resuscitation method or resuscitation on membrane filters, the bacterial counts on selective media matched those on non-selective media. Heat and light stress can affect the ability of E. coli to grow on selective media essential for the enumeration as indicator bacteria. A resuscitation method is essential for the recovery of these stressed bacteria in order to avoid underestimation of indicator bacteria numbers in water. There was no difference in resuscitation efficiency using the membrane filter and multi-well MPN methods. This study emphasises the need to use a resuscitation method if the numbers of indicator bacteria in water samples are not to be underestimated. False-negative results in the analysis of drinking water or natural bathing waters could have profound health effects.

Realising the maximum health benefits from water quality improvements in the home: a case from Zaka district, Zimbabwe

The provision of good quality household drinking water is often regarded as an important means of improving health. There are however indications that the microbiological quality of water deteriorates between source and point of use in the home. The notion that providing clean water sources could be the solution to the rural water supply problem might therefore not be correct. This paper presents the findings from a survey that sought to investigate the quality of water in the home post-collection and any factors that were contributing to the quality. The 24 households that participated in the study were selected randomly from two villages. Water samples were collected from the households and from the drinking water sources. These were tested for total coliforms and Escherichia coli. Greater contamination was detected in the water drawn from unprotected wells than in that drawn from protected ones. For protected sources, there was an increase in the numbers of pathogens in the stored water relative to the source water. In a few instances there was a decrease in indicator bacteria numbers following water collection. This could have been due to a natural die off of the pathogens. There however did not seem to be a significant correlation between the microbiological quality of water in the home and the length of time the water has been stored. These findings indicate that there is some deterioration in the microbiological quality of water post-collection and it appears the phenomenon may be attributable to water handling and hygiene behaviours in the home. Water was collected frequently and rarely treated after collection. Only one household out of the 24 reported treating their water after collecting it. Home water treatment or safe storage may be an appropriate intervention in this community to reduce diarrhoeal disease.