Bacteria In Water Samples Research Articles

Molecular identification of beta lactamase producing gram negative bacteria in water samples collected from River Yamuna in Agra Region

Molecular identification of beta lactamase producing gram negative bacteria in water samples collected from River Yamuna in Agra Region

Consumer Preferences for Water Supply at Njala University, Njala Campus in Southern Sierra Leone

Suppliers of potable water would benefit from a sustainable business as long as consumers continue to prefer their brand. Some of the reasons for choosing a particular brand include water quality, cost of the finished product, reliability of supply, and supplier ethics. These important determinant factors form the basis of this work. The objective is to delineate consumer preferences for water supplied to the Njala campus community, in southern Sierra Leone, and the underlying determinant factors. A list of questions administered to 140 respondents, are used to help achieve the objective. The results of water quality tests are also used to determine if quality has anything to do with consumer preference. The Oxfam Delagua water testing kit is customized to incubate and enhance counting of fecal and no-fecal coliform bacteria in water samples. Bacterial contamination is the major concern in the study area. The survey results reveal the consumers prefer package water for drinking. Treated water from Tia River is only used for other domestic purposes. The consumers do not trust the quality of water supplied from Tia River, albeit filtration and disinfection at the University’s treatment center. This distrust is confirmed by the bacterial test. None of the campus water sources meet recommended guidelines for drinking water. The consumers are, however, willing to shift preference from package to tap drinking water if treatment comes with quality assurance. The university could benefit through economic gratification, customer protection, and reduced plastic waste from package drinking water.

An Assessment of Coliform Bacteria in Water Sources Near Appalachian Trail Shelters Within the Great Smoky Mountains National Park

Hikers and campers are exposed to risks while in the wilderness. One of these risks is the possibility of contracting an illness, including infectious diarrhea. This project tested for coliform bacteria in water samples taken near popular Appalachian Trail shelters. Water was collected from access points within the Great Smoky Mountains National Park. Samples were collected in sterile bottles and inoculated on a commercially available coliform detection kit for quantitative determination of total coliform and Escherichia coli counts. Water samples were taken during summer and fall seasons. During summer, 7 of 10 samples were positive for coliform bacteria and 6 of those 7 for E coli. The most probable number (MPN) of colony-forming units (CFU) for coliform bacteria ranged from 0 to 489 CFU/100 mL, with the MPN for E coli varying from 0 to 123 CFU/100 mL. These data differed from the fall collection, revealing 3 of 7 samples positive for coliform bacteria and 1 of those 3 for E coli. The MPN of CFU for coliform bacteria in fall samples varied from 0 to 119 CFU/100 mL and 0 to 5 to CFU/100 mL for E coli. Environmental Protection Agency drinking water standards set the standard of 0 CFU/100 mL to be considered safe. This analysis of water samples along the Appalachian Trail emphasizes that the majority of water access points require treatment during the summer season. Coliform burden was not as high through the fall months. These data suggest one infectious disease risk for wilderness travelers.

Prevalence of Legionella pneumophila in water distribution systems in hospitals and public buildings of the Lublin region of eastern Poland.

The aim of this study was to determine the prevalence of L. pneumophila in water supply systems, hospitals and public buildings in the Lublin region of eastern Poland. The study was carried out in 26 different objects in the Lublin region. The number of Legionella bacteria in water samples was determined by the membrane filtration method and/or by surface inoculation in accordance with the standards. The study showed the presence of L. pneumophila in 166 hot water samples (74.77%). In 34.33% (n=57) of water samples the count of tested bacteria exceeded the acceptable level of >100 CFU/100 ml. Of the samples where an acceptable level of bacteria was exceeded, 49 samples had an average level of L. pneumophila (100-1,000 CFU/100 ml), and the level in 8 samples was high (>1,000 CFU/100 ml). The water samples collected form the hot water supply system of hospitals and public buildings showed exceeded counts of L. pneumophila, indicating the risk of infection. The constant monitoring of water distribution systems is an important element of the control of infections caused by these organisms.

치과대학 임상 시뮬레이션 실습실 치과용 유니트 수계의 세균 오염도 조사

The water supplied from dental unit water systems (DUWS) in dentistry may be heavily contaminated with bacteria and thus may be a potential source of infection for both practice staff and patients. The aim of this study was to evaluate the level of heterotrophic bacteria and to confirm the presence of opportunistic pathogens from DUWS in student clinical simulation laboratory of college of dentistry. Water samples were collected from 36 ultrasonic scalers in student clinical simulation laboratory. The levels of heterotrophic bacteria in water samples were quantified by counting colony forming units (CFUs) on R2A agar media. In addition, opportunistic pathogens were detected by using the polymerase chain reaction (PCR) method. The mean CFUs were 16,095 CFU/ml for water samples and all of water samples exceeded current American Dental Association recommendations of 200 CFU/ml. Pseudomonas species and non-tuberculous Mycobacterium species were detected in the one sample and two samples, respectively, among the 36 water samples by the PCR with specific primers for these bacteria. Our study indicated that DUWS in student clinical simulation laboratory can cause potential infection in students and participants. This study suggested the dental unit water line management and wearing personal protective equipment in student clinical simulation laboratory will be needed to reduce bacterial contamination.

Mobile Water Kit (MWK): a smartphone compatible low-cost water monitoring system for rapid detection of total coliform and E. coli

In this work, we have developed and demonstrated a rapid and low-cost water monitoring sensor that can simultaneously detect total coliform and Escherichia coli (E. coli) bacteria in contaminated drinking water samples. The test method, called Mobile Water Kit (MWK), comprises a set of custom chemical reagents that would serve as colorimetric or fluorometric chemosensors, syringe filter units and a smartphone platform that would serve as the detection/analysis system. The MWK provides information about the presence/absence of total coliform and E. coli in water samples. The MWK has preliminarily been tested for its selectivity, sensitivity and accuracy, with samples of known concentrations of bacteria. The MWK has also been tested with contaminated water samples collected during the two field trials conducted in Canada and India, and the obtained results were confirmed with conventional laboratory methods. With this MWK, we were able to detect the total coliform and E. coli bacteria in water samples within 30 min or less, depending on the concentration of the bacteria. For one of the field samples, the MWK was able to detect the total coliform within 35 s, which is faster than any rapid test methods available in the market. This new technology can dramatically improve the response times for the outbreak of water-borne diseases and will help water managers and individuals to assess the quality of water sources.

English

Fungi and bacteria in water samples taken from various flooded areas in Narathiwat Province, Thailand, were investigated. They were isolated by filtration from water samples, and identified by examining macroscopic and microscopic features for fungi and using biochemical methods for bacteria. Nine species of filamentous fungi and two yeast species were isolated. Water contaminated with dermatophytes contained Trichophyton mentagrophytes (44%), Trichophyton rubrum (19%) and Microsporum canis (15%). The yeast Candida albicans was also found (75.5%). Water samples were contaminated with fungi, identified as non-cutaneous mycoses. The dominant fungi were Aspergillus niger (73%), Cladosporium spp. (58%) and Aspergillus flavus (41%). Thirteen bacterial strains were isolated from the samples; Gram-negative bacteria were most prevalent. The three dominant Gram-negative bacteria were Escherichia coli (62.5%), Klebsiella pneumoniae (61%) and Enterobacter spp. (59.5%). The two most abundant Gram-positive bacteria were Corynebacterium spp. (59.5%) and Bacillus spp. (not Bacillus cereus) (52.5%). These results suggest contaminated flood areas may be a transmission route for pathogens, and increase the risk of abnormal skin conditions among people exposed to the area.   Key words: Flood, Thailand, fungus, bacteria, yeast.

English

Marine outfalls contribute to the environmental protection of coastal zones. However, these structures may serve as vehicles for microbiological contamination. This study aimed to investigate the occurrence of antimicrobial-resistant bacteria in water samples collected from 67 stations located in nearby areas of the ocean outfall in Fortaleza, Brazil. 81 Enterococcus strains were isolated, identified and distributed in the following groups of species: Enterococcus faecalis (n = 37; 45.7%), Enterococcus faecium (n = 30; 37%), Enterococcus mundtii (n = 9; 11.1%), Enterococcus raffinosus (n = 2; 2.5%), Enterococcus dispar (n = 2; 2.5%) and Enterococcus durans (n = 1; 1.2%). Antimicrobial resistance was observed in 47 (58%) of the strains, and the most predominant profile was the concurrent resistance to ampicillin, clindamycin, penicillin and vancomycin. In 31 strains were detected phenotypically, plasmid resistance factors. The data reported in this study should serve as an alert to public health authorities, since they suggest that the area near the submarine outfall in Fortaleza may contribute to antimicrobial-resistant enterococci spread. Key words: Enterococci, seawater, multidrug-resistant bacteria, public health.

Detection of Fecal Bacteria and Source Tracking Identifiers in Environmental Waters Using rRNA-Based RT-qPCR and rDNA-Based qPCR Assays

In this study, we evaluated the use of RT-qPCR assays targeting rRNA gene sequences for the detection of fecal bacteria in water samples. We challenged the RT-qPCR assays against RNA extracted from sewage effluent (n = 14), surface water (n = 30), and treated source water (n = 15) samples. Additionally, we applied the same assays using DNA as the qPCR template. The targeted fecal bacteria were present in most of the samples tested, although in several cases, the detection frequency increased when RNA was used as the template. For example, the majority of samples that tested positive for E. coli and Campylobacter spp. in surface waters, and for human-specific Bacteroidales, E. coli, and Enterococcus spp. in treated source waters were only detected when rRNA was used as the original template. The difference in detection frequency using rRNA or rDNA (rRNA gene) was sample- and assay-dependent, suggesting that the abundance of active and nonactive populations differed between samples. Statistical analyses for each population exhibiting multiple quantifiable results showed that the rRNA copy numbers were significantly higher than the rDNA counterparts (p < 0.05). Moreover, the detection frequency of rRNA-based assays were in better agreement with the culture-based results of E. coli, intestinal enterococci, and thermotolerant Campylobacter spp. in surface waters than that of rDNA-based assays, suggesting that rRNA signals were associated to active bacterial populations. Our data show that using rRNA-based approaches significantly increases detection sensitivity for common fecal bacteria in environmental waters. These findings have important implications for microbial water quality monitoring and public health risk assessments.

Analysis of microbial community structure in an integrated pond recirculating aquaculture system

Aquaculture has been one of the fastest growing segments of global food production sector in recent decades.With the rapid development,it also leads to many environmental problems.For example,both per unit area yield of aquatic products and their quality has declined continuously.It is important that well-balanced systems be developed that are sustainable.Constructed wetlands (CWs) are ecologically beneficial,low-cost treatment alternatives,proven capable of reducing suspended solids,5-day biochemical oxygen demand (BOD 5),nitrogen,phosphorus and heavy metals from wastewater of many sources.In the present paper,the physicochemical and microbial characteristics of culture ponds in an Integrated Pond Recirculating Aquaculture System (IPRAS) based on constructed wetland were investigated during the period of June to October 2008.In the study,16S rDNA gene V3 region was amplified from total DNA of bacteria in water samples and followed by DGGE.Sequences of 13 dominant bands excised from DGGE gels were analyzed and the closest relatives of obtained sequences were all uncultured bacterial clone in GenBank.The results indicated that levels of dissolved oxygen (DO) and transparency (SD) showed a decreasing trend along the flow direction (P1→P5),while an opposite trend for ammonium nitrogen (NH4+-N),total phosphorus (TP) and chemical oxygen demand (COD Mn).The recirculating treatment increased water DO and SD,while decreased pH,COD Mn and nutrients compared to the control.The DGGE fingerprints suggested a high species richness of microorganism and the clustering dendrogram revealed distinct differences in microbial community structure between the recirculating and control ponds.By the phylogenetic tree,the 13 dominant bands were grouped into four phyla:Actinobacteria,Proteobacteria,Cyanobacteria and Bacteroidetes,among which two cyanobacterial bands particular distributed in the control.The results of canonical correspondence analysis (CCA) also revealed that the distribution characteristics of DGGE fingerprints was strongly associated with the measured environment.Hereby,conclusions could be reached that the recirculating aquaculture system,as a new cultivation pattern,effectively improved the microbial environment of the culture ponds and benefited pond aquaculture.The results also provided basic references for analyzing the microbial community structure and their functional relationships in further study.

A new highly sensitive multi-walled carbon nanotubes based nano-fishing enriching rod for bacteria in water sample

Owing to the distinct properties,carbon nanotubes have been widely applied in biologic field.In this contribution,multi-walled carbon nanotubes were used as a nano-fishing enriching rod in targeting detection of bacteria in water sample.Single-stranded DNA (ssDNA) modified by amino group was linked to the silanized capillary through glutaral and then MWCNTs were immobilized through π-π interaction between DNA bases and MWCNTs,producing a nano-fishing rod device.Due to the high affinity between MWCNTs and cytomembrane,the device exhibited ability to actively hunt and capture the bacteria in aqueous solutions.It was found that using E.coli as targeted bacteria,the optimal detection time of nano-fishing rod device is 15 min and the detection limit is 6.25×10 CFU/mL.The novel device can find applications in real-time detection of total bacterial number in drinking water .

Analysis of the structure of bacteria communities and detection of resistance genes of quinolones from pharmaceutical wastewater

The aim of the present study was to investigate the distribution of bacteria and detect the presence of quinolone resistance gene (qnrA) and integrons (intI1, intI2) in a habitat polluted by pharmaceutical sewage. The bacteria were isolated by nutrient agar and nutrient broth from waste water and sludge collected from the sewage outfall of a pharmaceutical factory. The bacteria were identified by Gram staining and biochemical tests, and the bacterial community diversity was analyzed by Shannon–Wiener diversity index (H), Pielou evenness index (J) and Simpson’s diversity index (D). The occurrence of qnrA and integrons (intI1, intI2) were detected by Real-time PCR assays. The results showed that 90 strains were isolated from water samples and sludge samples including 22 genera and 26 species. Types of bacteria in water samples contained 18 genera and 20 species, while 13 genera and 14 species were detected in sludge samples. Fifty-five Enterobacteriaceae isolates (61.11 %, 55 of 90) were the predominant bacteria in water and sludge samples. Bacterial species richness and evenness in water samples were higher than in sludge samples. The resistance genes of qnrA and integrons (intI1, intI2) with the total DNA and single isolate plasmid DNA were detected. There were a variety of bacterial species and the presence of qnrA and integrons (intI1, intI2) genes in pharmaceutical wastewater habitats, in which Enterobacteriaceae strains were the dominant bacteria. These results suggested that pharmaceutical wastewater had potential risks to public health.

Faecal contamination of public water sources in informal settlements of Kisumu City, western Kenya

High levels of environmental contamination, often associated with improper waste and excreta management, are widespread among informal settlements within urban areas in developing countries. We determined the level of faecal contamination in domestic water sources and evaluated the potential contribution of these water sources to intestinal helminthiases in seven informal settlements of Kisumu City, western Kenya. Membrane filtration technique was used for enumeration of total and faecal (Escherichia coli) coliform bacteria in water samples collected from dams, rivers, springs and wells. Out of the 80 water sources sampled, 76 (95%) were highly contaminated with E coli. All water samples from unprotected wells (26) and 92.6% of samples from protected wells (25) were positive for E. coli. The highest and lowest E. coli densities were observed in samples from dams (3,800 ± 1,807 coliforms per 100 ml) and boreholes (419 ± 223 coliforms per 100 ml), respectively (p = 0.0321). Distance from pit latrines was negatively associated with E. coli coliform density for wells (r = -0.34, n = 53, p = 0.0142). Untreated well-water may not be suitable for human consumption, and its continued use constitutes a major health risk for the inhabitants of these informal settlements.

Phenotypic characterization and 16S rDNA identification of culturable non-obligate halophilic bacterial communities from a hypersaline lake, La Sal del Rey, in extreme South Texas (USA)

BackgroundLa Sal del Rey ("the King's Salt") is one of several naturally-occurring salt lakes in Hidalgo County, Texas and is part of the Lower Rio Grande Valley National Wildlife Refuge. The research objective was to isolate and characterize halophilic microorganisms from La Sal del Rey. Water samples were collected from the lake and a small creek that feeds into the lake. Soil samples were collected from land adjacent to the water sample locations. Sample salinity was determined using a refractometer. Samples were diluted and cultured on a synthetic saline medium to grow halophilic bacteria. The density of halophiles was estimated by viable plate counts. A collection of isolates was selected, gram-stained, tested for catalase, and characterized using API 20E® test strips. Isolates were putatively identified by sequencing the 16S rDNA. Carbon source utilization by the microbial community from each sample site was examined using EcoPlate™ assays and the carbon utilization total activity of the community was determined.ResultsResults showed that salinity ranged from 4 parts per thousand (ppt) at the lake water source to 420 ppt in water samples taken just along the lake shore. The density of halophilic bacteria in water samples ranged from 1.2 × 102 - 5.2 × 103 colony forming units per ml (cfu ml-1) whereas the density in soil samples ranged from 4.0 × 105 - 2.5 × 106 colony forming units per gram (cfu g-1). In general, as salinity increased the density of the bacterial community decreased. Microbial communities from water and soil samples were able to utilize 12 - 31 carbon substrates. The greatest number of substrates utilized was by water-borne communities compared to soil-based communities, especially at lower salinities. The majority of bacteria isolated were gram-negative, catalase-positive, rods. Biochemical profiles constructed from API 20E® test strips showed that bacterial isolates from low-salinity water samples (4 ppt) showed the greatest phenotypic diversity with regards to the types and number of positive tests from the strip. Isolates taken from water samples at the highest salinity (420 ppt) tended to be less diverse and have only a limited number of positive tests. Sequencing of 16S DNA displayed the presence of members of bacterial genera Bacillus, Halomonas, Pseudomonas, Exiguobacterium and others. The genus Bacillus was most commonly identified. None of the isolates were members of the Archaea probably due to dilution of salts in the samples.ConclusionsThe La Sal del Rey ecosystem supports a robust and diverse bacterial community despite the high salinity of the lake and soil. However, salinity does appear to a limiting factor with regards to the density and diversity of the bacterial communities that inhabit the lake and surrounding area.

Application of EMA-qPCR as a complementary tool for the detection and monitoring of Legionella in different water systems

Legionella are prevalent in human-made water systems and cause legionellosis in humans. Conventional culturing and polymerase chain reaction (PCR) techniques are not sufficiently accurate for the quantitative analysis of live Legionella bacteria in water samples because of the presence of viable but nonculturable cells and dead cells. Here, we report a rapid detection method for viable Legionella that combines ethidium monoazide (EMA) with quantitative real-time PCR (qPCR) and apply this method to detect Legionella in a large number of water samples from different sources. Results yielded that samples treated with 5 μg/ml EMA for 10 min and subsequently exposed to light irradiation for 5 min were optimal for detecting Legionella. EMA treatment before qPCR could block the signal from approximately 4 log(10) of dead cells. When investigating environmental water samples, the percent-positive rate obtained by EMA-qPCR was significantly higher than conventional PCR and culture methods, and slightly lower than qPCR. The bacterial count of Legionella determined by EMA-qPCR were mostly greater than those determined by culture assays and lower than those determined by qPCR. Acceptable correlations were found between the EMA-qPCR and qPCR results for cooling towers, piped water and hot spring water samples (r = 0.849, P < 0.001) and also found between the EMA-qPCR and culture results for hot spring water samples (r = 0.698, P < 0.001). The results indicate that EMA-qPCR could be used as a complementary tool for the detection and monitoring of Legionella in water systems, especially in hot spring water samples.

Development and validation of a FISH-based method for the detection and quantification of E. coli and coliform bacteria in water samples

Monitoring of microbiological contaminants in water supplies requires fast and sensitive methods for the specific detection of indicator organisms or pathogens. We developed a protocol for the simultaneous detection of E. coli and coliform bacteria based on the Fluorescence in situ Hybridization (FISH) technology. This protocol consists of two approaches. The first allows the direct detection of single E. coli and coliform bacterial cells on the filter membranes. The second approach includes incubation of the filter membranes on a nutrient agar plate and subsequent detection of the grown micro-colonies. Both approaches were validated using drinking water samples spiked with pure cultures and naturally contaminated water samples. The effects of heat, chlorine and UV disinfection were also investigated. The micro-colony approach yielded very good results for all samples and conditions tested, and thus can be thoroughly recommended for usage as an alternative method to detect E. coli and coliform bacteria in water samples. However, during this study, some limitations became visible for the single cell approach. The method cannot be applied for water samples which have been disinfected by UV irradiation. In addition, our results indicated that green fluorescent dyes are not suitable to be used with chlorine disinfected samples.

Microbiological risk assessment and sanitary inspection survey of Tefenni (Burdur/Turkey) region

The aim of the study was to examine microbiological risk of public water system of Tefenni (Burdur) region, which is located in southwest of Turkey. The important pollutants of the study area are cattle breeding, use of animal manure for agricultural activities and unsanitary water supply system and water tank. The microbiological condition was assessed using total coliform bacteria in water samples, which was collected from springs, wells and water supply system of Tefenni county and villages during the period January 2009 and December 2009. Microbiological analyses indicate that failure rate (positive samples) was 43% for sampling period. There was greater consistency among failures of total coliform indicator standards during spring and winter than during autumn and summer. This observation was explained partially by a significant positive correlation with the rainfall amount (rPearson = 0.70, P = 0.01). In addition, the microbiological risk assessment was made using modified sanitary inspection forms and prepared final score map. Compared with final score and microbial pollutant maps of the study area, it has been shown that water resources having high risk score were directly proportional with pollutants related to land use.

A rapid detection method using flow cytometry to monitor the risk of Legionella in bath water

Legionella species are the causative agents of human legionellosis, and bathing facilities have been identified as the sources of infection in several outbreaks in Japan. Researchers in Japan have recently reported evidence of significant associations between bacterial counts and the occurrence of Legionella in bathing facilities and in a hot tub model. A convenient and quantitative bacterial enumeration method is therefore required as an indicator of Legionella contamination or disinfection to replace existing methods such as time-consuming Legionella culture and expensive Legionella-DNA amplification. In this study, we developed a rapid detection method (RDM) to monitor the risk of Legionella using an automated microbial analyzing device based on flow cytometry techniques to measure the total number of bacteria in water samples within two minutes, by detecting typical patterns of scattered light and fluorescence. We first compared the results of our RDM with plate counting results for five filtered hot spring water samples spiked with three species of bacteria, including Legionella. Inactivation of these samples by chlorine was also assessed by the RDM, a live/dead bacterial fluorescence assay and plate counting. Using the RDM, the lower limit of quantitative bacterial counts in the spiked samples was determined as 3.0×103(3.48log)countsmL−1. We then used a laboratory model of a hot tub and found that the RDM could monitor the growth curve of naturally occurring heterotrophic bacteria with 1 and 2days' delayed growth of amoeba and Legionella, respectively, and could also determine the killing curve of these bacteria by chlorination. Finally, samples with ≥3.48 or <3.48logtotal bacterial countsmL−1 were tested using the RDM from 149 different hot tubs, and were found to be significantly associated with the positive or negative detection of Legionella with 95% sensitivity and 84% specificity. These findings indicated that the RDM can be used for Legionella control at bathing facilities, especially those where the effectiveness of chlorine is reduced by the presence of Fe2+, Mn2+, NH4+, skin debris, and/or biofilms in the water.

Automated measurement and quantification of heterotrophic bacteria in water samples based on the MPN method

Quantification of heterotrophic bacteria is a widely used measure for water analysis. Especially in terms of drinking water analysis, testing for microorganisms is strictly regulated by the European Drinking Water Directive, including quality criteria and detection limits. The quantification procedure presented in this study is based on the most probable number (MPN) method, which was adapted to comply with the need for a quick and easy screening tool for different kinds of water samples as well as varying microbial loads. Replacing tubes with 24-well titer plates for cultivation of bacteria drastically reduces the amount of culture media and also simplifies incubation. Automated photometric measurement of turbidity instead of visual evaluation of bacterial growth avoids misinterpretation by operators. Definition of a threshold ensures definite and user-independent determination of microbial growth. Calculation of the MPN itself is done using a program provided by the US Food and Drug Administration (FDA). For evaluation of the method, real water samples of different origins as well as pure cultures of bacteria were analyzed in parallel with the conventional plating methods. Thus, the procedure described requires less preparation time, reduces costs and ensures both stable and reliable results for water samples.

Lanthanum-based concentration and microrespirometric detection of microbes in water

Rapid concentration and detection of microorganisms, particularly pathogens, are important but remain a challenge. In this research, lanthanum chloride (LaCl 3) was used to concentrate E. coli in water and the results were compared with those obtained using traditional flocculants, such as ferric sulfate and aluminum sulfate. A turbidimetric assay and a microrespirometric assay were employed to enumerate the bacteria in water samples by monitoring the absorbance of bacteria and the oxygen-based fluorescence intensity, respectively. The microrespirometric method requires less time than the turbidimetric assay. Both assays could linearly enumerate the bacteria at the concentration range from 10 1 to 10 9 cells/mL. Based on the turbidimetric assay, the relative concentration efficiencies of the three flocculants were 75% (LaCl 3), 40% (FeCl 3) and 33% (Al 2(SO 4) 3), while for the microrespirometric assay, the concentration efficiencies were 85% (LaCl 3), 34% (FeCl 3) and 32% (Al 2(SO 4) 3). The microbial recovery rates, defined as the ratio of cell number in the sediment after coagulation/flocculation to that of the controls, were 94% (LaCl 3), 69% (FeCl 3) and 51% (Al 2(SO 4) 3) from the turbidimetric assay. The results demonstrate that compared with traditional flocculants, LaCl 3 has higher relative concentration and recovery efficiencies and thus possesses the potential for microbial concentration in water samples.