Determination of low-density Escherichia coli and Helicobacter pylori suspensions in water

Helicobacter pylori virulence genotypes in Bogotá River and wastewater treatment plants in Colombia

BACKGROUND

Helicobacter pylori is a bacterium that infects 70%-80% of the population in Colombia, causing chronic gastritis in all those infected and gastric cancer in 1%-2% of those infected. In Colombia, some studies have identified the presence of vacA and cagA genes in environmental samples such as treated, surface, and wastewater, but they have not been evaluated in the Bogotá River. For this, the aim of this study was to identify the virulence genotypes of H. pylori present in samples from the Bogotá River and domestic wastewater treatment plants (WWTPs).

MATERIALS AND METHODS

A total of 75 water samples (51 from the Bogotá River and 24 from wastewater treatment plants) were collected. The presence of H. pylori DNA and its virulence genotypes was determined by polymerase chain reaction (PCR).

RESULTS

The presence of H. pylori DNA was demonstrated in 44% (33/75) of the samples, obtaining 63.6% (21/33) from the Bogotá River and 36.4% (12/33) from the WWTPs. The most prevalent H. pylori genotype was cagA (-) and vacAm1/s1/i1 being the most virulent of the vacA gene.

CONCLUSIONS

This is the first study in Colombia that determines the cagA and vacA genotypes in surface water and WWTPs, indicating the circulation of virulent genotypes in the population. The presence of this pathogen in the waters can be represent a risk to the health of the surrounding population since these waters are reused by the communities for different purposes.

Macroporous epoxy-based monoliths for rapid quantification of Pseudomonas aeruginosa by adsorption elution method optimized for qPCR

Pseudomonas aeruginosa contaminations in tap water systems have caused severe health problems in both hospital and household settings. To ensure fast and reliable detection, culture-independent methods are recommendable. However, the typically low cell number in water samples requires sample enrichment prior to analysis. Therefore, we developed and optimized an adsorption elution method using monolithic adsorption filtration and subsequent centrifugal ultrafiltration that can be combined with culture-independent detection methods. The principle of adsorption of Pseudomonas aeruginosa by hydrophobic and ionic interactions was studied in modified epoxy-based monoliths. Optimized conditions (5-L initial sample volume at pH 3 filtered for 30 min through hydrolyzed monoliths (MAF-OH) and eluted with beef extract glycine buffer at pH 9.5) achieved a recovery of 67.1 ± 1.2% and a concentration factor of 10³. For the first time, we therefore present a culture-independent approach for rapid enrichment and subsequent molecular biological quantification of P. aeruginosa by qPCR from tap water samples by monolithic adsorption filtration. The total enrichment and quantification process takes 4 h. This work further stresses the versatility of the monolithic adsorption filtration and its possibilities as a concentration tool for culture-independent analytics of pathogenic bacteria in the environment.

Graphical abstract

Fast, sensitive, and reliable detection of waterborne pathogens by digital PCR after coagulation and foam concentration

The quantification of pathogens is important for assessing water safety and preventing disease outbreaks. Culture-independent approaches, such as quantitative PCR (qPCR) and digital PCR (dPCR), are useful techniques for quantifying pathogens in water samples. However, since pathogens are usually present at low concentrations in water, it is necessary to concentrate microbial cells before extracting their DNA. Many existing microbial concentration methods are inefficient or take a long time to perform. In this study, we applied a coagulation and foam separation method to concentrate environmental water samples of between 1000 and 5000 mL to 100 μL of DNA (i.e., a 1-5 × 10⁴-fold concentration). The concentration process took <1 h. The DNA samples were then used to quantify various target pathogens using dPCR. One gene, the Shiga toxin gene (stx₂) of Shiga toxin-producing Escherichia coli, was detected at 32 copies/100 mL in a river water sample. The coagulation and foam concentration method followed by dPCR reported herein is a fast, sensitive, and reliable method to quantify pathogen genes in environmental water samples.

Advancements in mitigating interference in quantitative polymerase chain reaction (qPCR) for microbial water quality monitoring

The United States Environmental Protection Agency's (EPA)¹ 2012 Recreational Water Quality Criteria included an Enterococcus spp. quantitative polymerase chain reaction (qPCR) method as a supplemental indicator-method. In 2012, performance of qPCR for beach monitoring remained limited, specifically with addressing interference. A systematic literature search of peer-reviewed publications was conducted to identify where Enterococcus spp. and E. coli qPCR methods have been applied in ambient waters. In the present study, we evaluated interference rates, contributing factors resulting in increased interference in these methods, and method improvements that reduced interference. Information on qPCR methods of interest and interference controls were reported in 16 papers for Enterococcus spp. and 13 papers for E. coli. Of the Enterococcus spp. qPCR methods assessed in this effort, the lowest frequencies of interference were reported in samples using Method 1609. Low frequencies of sample interference were also reported EPA's modified E. coli qPCR method, which incorporates the same reagents and interference controls as Method 1609. The literature indicates that more work is needed to demonstrate the utility of E. coli qPCR for widespread beach monitoring purposes, whereas more broad use of Method 1609 for Enterococcus spp. is appropriate when the required and suggested controls are employed.

Correlation among fecal indicator bacteria and physicochemical parameters with the presence of Helicobacter pylori DNA in raw and drinking water from Bogotá, Colombia

BACKGROUND

The quality of raw and drinking water is a matter of considerable concern due to the possibility of fecal contamination. To assess the quality and public health risk of different types of water, the fecal indicator bacteria (FIB) are used. However, some pathogens, such as Helicobacter pylori, may be present in water when FIB cannot be found. H pylori is recognized as the causative agent of chronic gastritis, peptic and duodenal ulcers, and gastric cancer. The aim of this study was to evaluate the relationships among physicochemical parameters, FIB concentrations, and the presence of H pylori DNA in raw and drinking water from Bogotá, Colombia.

MATERIALS AND METHODS

A total of 310 water samples were collected 1 day per week from July 2015 to August 2016, and physicochemical parameters (pH, turbidity, conductivity, and residual free chlorine) were measured. Presence of H pylori DNA was determined and quantified by quantitative polymerase chain reaction (qPCR). Fecal indicator bacteria (total coliforms, Escherichia coli, and spores of sulfite-reducing Clostridia) were enumerated by using standard culture techniques.

RESULTS

Thirty of 155 (31%) raw water samples and forty-eight of 155 (38.7%) drinking water samples were positive for the presence of H pylori. No statistically significant relationships were found between physicochemical parameters or FIB with the presence or absence of H pylori in any sample (P < 0.05).

CONCLUSIONS

This study provides evidence of the presence of H pylori DNA in raw and drinking water in Bogotá, and shows that the detection and enumeration of FIB and physicochemical parameters in water do not correlate with the risk of contamination with H pylori.

Evaluation and modification of lanthanum-based flocculation for isolation of bacteria from water samples

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A published lanthanum-based flocculation protocol is evaluated for four bacterial species

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The success of lanthanum-based flocculation is determined by both the bacterial species and the nature of the water sample

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Addition of 20 mM bicarbonate significantly improve the flocculation efficiency for tap water

Molecular detection of pathogenic microorganisms in drinking and natural water is often challenged by low concentrations of the sought-after agents. Convenient methods to concentrate bacteria from water samples ranging from 1-10 L are highly warranted. Here we account for the evaluation of a lanthanum-based flocculation method to concentrate bacteria from water samples, applying four different bacterial species in tap water as well as river water. Our results show that the success of lanthanum-based flocculation is determined by both the bacterial species and the nature of the water sample. For tap water, satisfying flocculation efficiencies (above 60 %) were only reached for autoclaved water samples. However, the performance of the lanthanum-based flocculation method for non-autoclaved water was markedly improved by the addition of 20 mM bicarbonate to increase alkalinity. Our modified flocculation protocol may be applied as an alternative concentration method for bacteria in water samples of one liter or more.

On the track for an efficient detection of Escherichia coli in water: A review on PCR-based methods

Ensuring water safety is an ongoing challenge to public health providers. Assessing the presence of fecal contamination indicators in water is essential to protect public health from diseases caused by waterborne pathogens. For this purpose, the bacteria Escherichia coli has been used as the most reliable indicator of fecal contamination in water. The methods currently in use for monitoring the microbiological safety of water are based on culturing the microorganisms. However, these methods are not the desirable solution to prevent outbreaks as they provide the results with a considerable delay, lacking on specificity and sensitivity. Moreover, viable but non-culturable microorganisms, which may be present as a result of environmental stress or water treatment processes, are not detected by culture-based methods and, thus, may result in false-negative assessments of E. coli in water samples. These limitations may place public health at significant risk, leading to substantial monetary losses in health care and, additionally, in costs related with a reduced productivity in the area affected by the outbreak, and in costs supported by the water quality control departments involved. Molecular methods, particularly polymerase chain reaction-based methods, have been studied as an alternative technology to overcome the current limitations, as they offer the possibility to reduce the assay time, to improve the detection sensitivity and specificity, and to identify multiple targets and pathogens, including new or emerging strains. The variety of techniques and applications available for PCR-based methods has increased considerably and the costs involved have been substantially reduced, which together have contributed to the potential standardization of these techniques. However, they still require further refinement in order to be standardized and applied to the variety of environmental waters and their specific characteristics. The PCR-based methods under development for monitoring the presence of E. coli in water are here discussed. Special emphasis is given to methodologies that avoid pre-enrichment during the water sample preparation process so that the assay time is reduced and the required legislated sensitivity is achieved. The advantages and limitations of these methods are also reviewed, contributing to a more comprehensive overview toward a more conscious research in identifying E. coli in water.

Contaminated water as a source of Helicobacter pylori infection: A review

Over the preceding years and to date, the definitive mode of human infection by Helicobacter pylori has remained largely unknown and has thus gained the interest of researchers around the world. Numerous studies investigated possible sources of transmission of this emerging carcinogenic pathogen that colonizes >50% of humans, in many of which contaminated water is mentioned as a major cause. The infection rate is especially higher in developing countries, where contaminated water, combined with social hardships and poor sanitary conditions, plays a key role. Judging from the growing global population and the changing climate, the rate is expected to rise. Here, we sum up the current views of the water transmission hypothesis, and we discuss its implications.

Development of a virus concentration method using lanthanum-based chemical flocculation coupled with modified membrane filtration procedures

Direct membrane filtration is often used to concentrate viruses in water but it may suffer from severe membrane fouling and clogging. Here, a lanthanum-based flocculation method coupled with modified membrane filtration procedures was developed and evaluated to detect viruses in large volume (40 L) water samples. The lanthanum-based flocculation method could easily reduce the water sample volume by a factor of 40. Additional volume reduction was achieved by a two-step membrane filtration approach. First, selected membrane filters (including 1MDS electropositive filters and nitrocellulose electronegative filters-Millipore HATF filters) were used to reduce water sample volume further and compare their efficiencies in virus recovery. The Mg²⁺-modified HATF membrane performed better on MS2 retention with an average virus recovery of 83.4% (±4.5% [standard deviation]). After HATF membrane filtration and elution, centrifugal ultrafiltration through a 30 kDa cut-off membrane resulted in an overall concentration factor of 20,000. Results from the infectivity assay showed that the MS2 recovery efficiencies from the NanoCeram- and 1MDS-based direct filtration and the lanthanum-based concentration coupled with the modified filtration procedure were 10.1% (±1.0%), 3.3% (±0.1%), and 17.5% (±1.1%), respectively. Results from the PCR analysis showed that the virus recoveries of the lanthanum-based method were 20.6% (±2.9%) and 19.5% (±3.4%) for MS2 and adenovirus, respectively, while no adenovirus could be detected through the NanoCeram- and 1MDS-based direct filtration. The lanthanum-based concentration method coupled with modified membrane filtration procedures is therefore a promising method for detecting waterborne viruses.