Microbial monitoring of surface water in South Africa: an overview

A regulatory framework for bottled water quality monitoring: A case of Emfuleni local municipality

Background

The quality of drinking water has recently become of utmost concern to consumers worldwide, especially in areas where Water Service Authorities (WSAs) failed to provide safe water. To combat this challenge, government entities regulate water to ensure that safe water is provided. The Emfuleni Local Municipality (ELM) has experienced cases of water contamination by human excretion, whereby communities were affected. As a result, there was a sharp increase in bottled water (BW) use, which however gave rise to unregulated and counterfeit versions of popular brands. This situation poses threats to public health.

Aim

This study sought to determine the regulation of drinking water and to assess whether environmental health practitioners (EHPs) monitor the quality of water sources (BW and tap water) in ELM as outlined by the National Environmental Health Norms and Standards (NEHNS).

Settings

The study was conducted in the Emfuleni Local Municipality in South Africa.

Methods

A quantitative cross-sectional study design was employed in this research. Fifteen online questionnaires using a Google Forms survey were distributed amongst all EHPs servicing ELM. Secondary data that included the Integrated Development Plan (IDP) and Service Delivery Budget Implentation Plan (SDBIP) for the 2017-2020 financial years were also evaluated, specifically for water quality monitoring (tap and bottled water). The dataset was analysed using the Statistical Package for the Social Sciences (SPSS) version 29.

Results

Due to complexity in the legislation and NEHNS in relation to Municipal Health Services (MHS), bottled water was not sampled at all. A number of EHPs were also not conversant with the regulations governing BW. Moreover, NEHNS consider bottled water as food, which does not fall under the MHS.

Conclusion

There should be clarity in the legislation to ensure that bottled water monitoring is intensified to protect public health within the WSAs.

Contribution

The findings of this study could assist policy-makers to make informed decisions on water quality monitoring, as well as clarify legislative issues on bottled water.

Multifunctional Heterogeneous Ion-Exchange Membranes for Ion and Microbe Removal in Low-Salinity Water

Here, multifunctional heterogeneous ion-exchange metal nanocomposite membranes were prepared for surface water desalination and bacterial inactivation under low-pressure (0.05 MPa) filtration conditions. Ultrafiltration (UF) heterogeneous ion exchange membranes (IEMs) were modified with different concentrations of AgNO₃ and CuSO₄ solutions using the intermatrix synthesis (IMS) technique to produce metal nanocomposite membranes. Scanning electron microscopy (SEM) images revealed that the metal nanoparticles (MNPs) (Ag and Cu) were uniformly distributed on the surface and the interior of the nanocomposite membranes. With increasing metal precursor solution concentration (0.01 to 0.05 mol·L^-1), the metal content of Ag and Cu nanocomposite membranes increased from 0.020 to 0.084 mg·cm^-2 and from 0.031 to 0.218 m·cm^-2 respectively. Results showed that the hydrodynamic diameter diameters of Ag and Cu nanoparticles (NPs) increased from 62.42 to 121.10 nm and from 54.2 to 125.7 nm respectively, as the metal precursor concentration loaded increased. The leaching of metals from metal nanocomposite membranes was measured in a dead-end filtration system, and the highest leaching concentration levels were 8.72 ppb and 5.32 ppb for Ag and Cu, respectively. The salt rejection studies indicated that ionic selectivity was improved with increasing metal content. Bacterial filtration showed higher antibacterial activity for metal nanocomposite membranes, reaching 3.6 log bacterial inactivation.

Water quality modelling and quantitative microbial risk assessment for uMsunduzi River in South Africa

South African rivers generally receive waste from inadequate wastewater infrastructure, mines, and farming activities, among others. The uMsunduzi River in KwaZulu-Natal, South Africa, is among these recipients with recorded poor to very poor water quality. To identify parts of the uMsunduzi River that are polluted by Cryptosporidium and Escherichia coli (E. coli), this study mapped out pollutants emanating from point and non-point sources using the Soil and Water Assessment Tool (SWAT). Streamflow calibration in the upper and lower reaches of the catchment showed good performance with R² of 0.64 and 0.58, respectively. SWAT water quality output data were combined with a Quantitative Microbial Risk Assessment (QMRA) to understand the microbial health implications for people using river water for drinking, recreational swimming, and non-competitive canoeing. QMRA results for Cryptosporidium and pathogenic E. coli showed that the probability of infection for most users exceeds the acceptable level for drinking and recreation as outlined in the South African water quality guidelines, and by the World Health Organization (WHO). The results of this study can be used as a baseline to assess the economic and health implications of different management plans, resulting in better-informed, cost-effective, and impactful decision-making.

Culture independent DNA extraction method for bacterial cells concentrated from water

•

To bypass the problem of viable but non-culturable bacteria that cannot be isolated by culturable methods would be to isolate DNA from bacterial cells concentrated from water samples used as a template for the polymerase chain reactions (PCR). DNA extraction protocol (Omar et al. 2010) was used as a foundation for extracting Escherichia coli DNA from water. The method combinations i.e., guanidium thiocyanate, celite and home-made spin column were chosen because it has been shown to be reliable, rapid, simple, and inexpensive for routine analysis in developing country settings.

•

The following optimizations were included: (a) Polycarbonate (Poly) was statistically compared with Polyether sulphone (PES), Nitrocellulose acetate (NA) and Nitrocellulose (NC) membranes; (b) Various housing containers for the membranes were tested: plastic/glass petri-dish, Falcon tubes, Ogreiner cryovials; (c) various solutions was tested to add to the membrane to remove cells from membranes; (d) celite was chosen to bind the DNA because it had a higher DNA binding capacity compared to silicon dioxide; (e) incubation times and rotation speed were tested when adding reagents.

•

The optimized in-house DNA extraction method was validated with environmental water samples, high (dam water) and low (borehole) bacterial load to determine upper and lower detection limits of the method.

Prevalence and characteristics of Listeria species from selected African countries

Listeriosis, caused by Listeria spp., presents varying clinical manifestations among individuals, from moderate fecal infections such as diarrhea to severe infections such as septicemia, meningitis and abortion or newborn listeriosis in perinatal patients. In Africa, listeriosis is attributed to poor sanitation and cross-contamination in food processing environments, particularly ready to eat (RTE) foods including dairy products, leafy vegetables, fish and meat. Despite the global increase in reported cases and research on listeriosis, data from Africa remains scarce and this could lead to possible underestimation of the importance of listeriosis on the continent. This paper therefore presents a comprehensive overview of currently available reports on Listeria spp. in Africa with emphasis on molecular characteristics, antimicrobial susceptibility, and prevalence in food, animal and environmental samples. The majority of studies on Listeria spp. in Africa have so far focused on the prevalence and antibiotic susceptibility of L. monocytogenes isolated from RTE foods and raw meat but rarely from humans, animals, and the environment. The overall calculated average prevalence values from the available reports are 23.7 and 22.2% for Listeria spp. and L. monocytogenes, respectively. Listeria spp. isolated from different parts of Africa are generally sensitive to ciprofloxacin, but resistant to penicillin. The majority of these studies employed conventional culture and biochemical tests to characterize Listeria spp. However, the use of modern molecular techniques such as PCR and whole-genome sequencing is on the rise. Most of the studies employing molecular tools were carried out in South Africa and Nigeria, with the predominant strain reported in South Africa being ST6. In order to provide a better understanding of the importance of listeria in Africa, there is the need for extensive and coordinated studies using modern molecular-based techniques to characterize the various Listeria species, and to assess the disease epidemiology using the one health concept.

Investigation into the bacterial diversity of sediment samples obtained from Berg River, Western Cape, South Africa

This study used conventional culturing and 16S rRNA metagenomics analyses to assess the diversity of bacterial communities in sediment samples obtained from the Berg River, Western Cape, South Africa. Samples were collected from six points: a residential and recreational area, an industrial area, an informal residential settlement, a point next to a wastewater treatment plant (WWTP), a pumping station, and a residential and agricultural farming area along the river. High bacterial counts recorded on general selective and differential culture media signify substantial microbial contamination along the sampling sites. The most prevalent bacterial phyla detected (through metagenomics analyses) along the sampling sites were Proteobacteria (61%), Planctomycetes (9.5%), Firmicutes (7.8%), Bacteroidetes (5%), Acidobacteria (4.6%), and Actinobacteria (4.6%). Some members of the identified predominant bacterial phyla, genera, and classes are important public health bacteria that have been implicated in human diseases and outbreaks, while some others are metal or hydrocarbon tolerant, indicating possible significant environmental pollution. Notable human pathogenic genera such as Bacillus, Clostridium, Shigella, Legionella, Mycobacterium, and Pseudomonas were identified in varying percentages at five of the six sampling areas. Fecal contamination was particularly rife at all residential areas, with the informal housing area being the most notably polluted. Diverse functional pathways were predicted for identified bacteria, such as those associated with different chronic and infectious human diseases as well as those related to hydrocarbon and metal remediation. The point next to a WWTP contained vastly diverse groups of bacterial contaminants as well as the most abundant pathway identities and titles.

Proposal of a pathway for enteric virus groups detection as indicators of faecal contamination to enhance the evaluation of microbiological quality in freshwater in Argentina

An environmental survey was conducted in order to assess the frequency of detection of picobirnavirus (PBV), human adenovirus (HAdV) and infective enterovirus (iEV) as indicators of faecal contamination in freshwater, and to determine their potential as reporters of the presence of other enteric viruses, such as group A rotavirus (RVA). The study was carried out over a three-year period (2013-2015) in the San Roque Dam, Córdoba, Argentina. The overall frequency detection was 62.9% for PBV, 64.2% for HAdV and 70.4% for iEV. No significant differences were observed in the rates of detection for any of these viruses through the years studied, and a seasonal pattern was not present. Whenever there was RVA detection in the samples analyzed, there was also detection of iEV and/or HAdV and/or PBV. At least one of the viral groups analyzed was demonstrated in the 100% of the samples with faecal coliforms values within the guideline limits. In this setting, especially in those samples which reveal faecal indicator bacteria within the guideline limit, we propose to carry out a pathway, involving PBV, HAdV and iEV detection in order to enhance the evaluation of microbiological quality in freshwater in Argentina. The proposed methodological strategy could report faecal contamination in water, mainly of human origin, and the condition of the matrix to maintain viral viability. In addition, the viral groups selected could report the presence of RV.

An outbreak of cutaneous abscesses caused by Panton-Valentine leukocidin-producing methicillin-susceptible Staphylococcus aureus among gold mine workers, South Africa, November 2017 to March 2018

BACKGROUND

We aimed to describe an outbreak of cutaneous abscesses caused by Panton-Valentine leukocidin (PVL)-producing methicillin-susceptible Staphylococcus aureus (MSSA) among gold mine workers.

METHODS

In February 2018, we retrospectively reviewed a random sample of 50 medical records from 243 cases and conducted face-to-face interviews using a structured questionnaire. Pus aspirates were sent to the National Institute for Communicable Diseases from prospectively-identified cases (November 2017-March 2018). Nasopharyngeal swabs were collected during a colonisation survey in February 2018. Staphylococcus aureus isolates were screened with a conventional PCR for lukS/F-PV. Pulsed-field gel electrophoresis (PFGE) was performed to determine the genetic relatedness among the isolates. A sample of isolates were selected for whole genome sequencing (WGS). We conducted an assessment on biological risks associated with mining activities.

RESULTS

From January 2017 to February 2018, 10% (350/3582) of mine workers sought care for cutaneous abscesses. Forty-seven medical files were available for review, 96% were male (n = 45) with a mean age of 43 years (SD = 7). About 52% (24/46) were involved in stoping and 28% (13/47) worked on a particular level. We cultured S. aureus from 79% (30/38) of cases with a submitted specimen and 14% (12/83) from colonisation swabs. All isolates were susceptible to cloxacillin. Seventy-one percent of S. aureus isolates (30/42) were PVL-PCR-positive. Six PFGE clusters were identified, 57% (21/37) were closely related. WGS analysis found nine different sequence types. PFGE and WGS analysis showed more than one cluster of S. aureus infections involving closely related isolates. Test reports for feed and product water of the mine showed that total plate counts were above the limits of 1000 cfu/ml, coliform counts > 10 cfu/100 ml and presence of faecal coliforms. Best practices were poorly implemented as some mine workers washed protective clothing with untreated water and hung them for drying at the underground surface.

CONCLUSIONS

PVL-producing MSSA caused an outbreak of cutaneous abscesses among underground workers at a gold mining company. To our knowledge, no other outbreaks of PVL-producing S. aureus involving skin and soft tissue infections have been reported in mining facilities in South Africa. We recommend that worker awareness of infection prevention and control practices be strengthened.

Combining physicochemical properties and microbiome data to evaluate the water quality of South African drinking water production plants

Anthropogenic activities in catchments used for drinking water production largely contaminates source waters, and this may impact the quality of the final drinking water product. These contaminants may also affect taxonomic and functional profiles of the bacterial communities in the drinking water. Here, we report an integrated insight into the microbiome and water quality of four water treatment plants (NWC, NWE, WCA and NWG) that supply portable water to communities in South Africa. A new scoring system based on combined significant changes of physicochemical parameters and microbial abundance from raw to treated water was used to evaluate the effectiveness of the treatment plants at water purification. Physicochemical parameters which include total soluble solids, turbidity, pH, nitrites and phosphorus among others, were measured in source, treated, and distributed water. There were general statistically significant (P ≤ 0.05) differences between raw and treated water, demonstrating the effectiveness of the purification process. Illumina sequencing of the 16S rRNA gene was used for taxonomic profiling of the microbial communities and this data was used to infer functional attributes of the communities. Structure and composition of the bacterial communities differed significantly (P < 0.05) among the treatment plants, only NWE and NWG showed no significant differences (P > 0.05), this correlated with the predicted functional profile of the microbial communities obtained from Phylogenetic Investigation of Communities by Reconstruction of Observed States (PICRUSt), as well as the likely pollutants of source water. Bacteroidetes, Chlorobi and Fibrobacteres significantly differed (P < 0.05) between raw and distributed water. PICRUSt inferred a number of pathways involved in the degradation of xenobiotics such as Dichlorodiphenyltrichloroethane, atrazine and polycyclic aromatic hydrocarbons. More worryingly, was the presence of pathways involved in beta-lactam resistance, potential pathogenic Escherichia coli infection, Vibrio cholerae infection, and Shigellosis. Also present in drinking and treated water were OTUs associated with a number of opportunistic pathogens.

Rare earth elements (REE) in the urban wastewater of Cotonou (Benin, West Africa)

The rare earth element (REE) contamination of urban wastewater, which was collected from open sewers and the inlet of a wastewater treatment plant in Cotonou (Benin), was assessed. The drinking water distributed to the inhabitants of Cotonou and water samples from private wells were also analyzed. The sampling occurred between October and December 2016 and the samples were analyzed by ICP-MS. Although the only magnetic resonance imaging facility in Cotonou opened in November 2016, pollution by anthropogenic gadolinium (Gd), which is included in phase contrast agents, was observed: there was 30-620 times more Gd in wastewater samples than in drinking and well water samples. Europium was another REE presenting positive anomalies. It is hypothetized than the europium came from the leachates of solid waste piles in the street. In the absence of any wastewater treatment, the REEs found in the wastewater are spread to the aquatic environment. It would be interesting to monitor the wastewater REEs over the long term. So far, the aquifers used for water provision have not been polluted by the anthropogenic REEs.

The efficiency of a low-cost hydrogen sulphide (H2S) kit as an early warning test for assessing microbial rainwater quality and its correlation with standard indicators microorganisms

Testing microbial quality of the harvested rainwater remains a challenge in many countries. The H2S test kit is a low-cost microbiological field-based test which can be used in areas where water testing facilities are limited. This study compares its efficiency with the standard indicators microorganisms in the detection of faecal contamination of rainwater in South Africa. A total of 88 rainwater samples were collected from various tanks in the Eastern Cape, South Africa over three months in 2016. The collected samples were analysed for faecal bacterial contamination using the H2S test kit, Colilert-18/Quanti-tray®/2000 and the membrane filtration technique for faecal coliforms (MFT). The correspondence rate of the H2S test kit with MFT was 88 %, while for the Colilert®it was 76 %. The H2S test kit confirmed faecal contamination when concentrations of standards indicators microorganisms were 5 most-probable number of cells/100 cm3or higher. Overall, the best correspondence of the H2S test kit with Colilert®was observed atE. coliconcentrations above 50 most-probable number of cells/100 cm3. Results of the H2S test kit correlated better with MTF, while the medium used has strongly influenced the enumeration of faecal contamination. Results point to strong effect of media used and revealed the need to calibrate the correspondence between the standard indicator microorganisms and the H2S test kit under local conditions for specific settings.

Prevalence and public health implications of mycotoxigenic fungi in treated drinking water systems

Insufficient potable water resources and poorly treated drinking water quality are the world's number one cause for preventable morbidity and mortality from water-related pathogenic microorganisms. Pathogenic microorganisms, including mycotoxigenic fungi, have been identified in treated drinking water. This paper presents a review of mycotoxigenic fungi as a health risk to the public as these fungi are responsible for allergies, cancers and opportunistic infections mainly to immunocompromised patients. The exacerbating factors contributing to fungal presence in water distribution systems, factors that lead to fungi being resistant to water treatment and treated drinking water quality legislations are also discussed. This paper provides a review on the prevalence of mycotoxigenic fungi and their implications to public health in treated drinking water, and the need for inclusion in treated drinking water quality regulations.

Development and field testing of low-cost, quantal microbial assays with volunteer reporting as scalable means of drinking water safety estimation

AIMS

To evaluate a low-cost water quality test for at-scale drinking water safety estimation in rural India.

METHODS AND RESULTS

Within a longitudinal study to characterize variability in household drinking water safety in rural Maharashtra, we piloted a low-cost presence-absence (LCPA) microbial test designed to be used by volunteer residents in rural areas. In comparing the LCPA results with standard laboratory methods for enumeration of Escherichia coli, we found that LCPA tests using modified mTec media were highly sensitive in detecting drinking water of moderate risk (88% of tests were positive at E. coli counts of 11-100 CFU per 100 ml) and high risk (96% of tests were positive at E. coli counts of 101 + CFU per 100 ml). The LCPA tests demonstrated low specificity for E. coli specifically, due to concurrent detection of Klebsiella: 38% of LCPA tests were positive even when E. coli was not detected in a 100 ml sample by membrane filtration, suggesting the test would be conservative in risk estimation. We also found that 47% of participants in rural villages in India were willing to conduct tests and return results after a brief training, with 45% of active participants sending their water testing results via short message service.

CONCLUSIONS

Given their low cost (~US$0.50 as piloted) and open-source format, such tests may provide a compelling alternative to standard methods for rapid water quality assessments, especially in resource-limited settings.

SIGNIFICANCE AND IMPACT OF THE STUDY

The lack of availability of water quality data constrains efforts to monitor, evaluate and improve the safety of water and sanitation infrastructure in underserved settings. Current water testing methods are not scalable because of laboratory and cost constraints. Our findings indicate the LCPA or similar low-cost microbial tests could be useful in rapid water safety estimation, including via crowdsourcing.

[A protocol for evaluating the probability of the recreational use of rivers and its application in risk analysis]

Contaminated waters constitute health risks not only due to direct consumption, but also in recreational use. Risk analysis strategies aim to reduce the instances of contaminations and must include the population's perceptions and willingness to assume risks. A rapid and simple method was developed to evaluate the probability of use of recreational waters. Interviews were conducted in municipalities with different ecological conditions, in order to define the factors used by people to decide to use, or otherwise, river waters. After analyzing the results, the "Índice de Probabilidade de Uso Recreativo de Águas (I-PURA)" was elaborated and tested. The index was then employed at 26 river locations representing five of the nine hydrographic regions of Rio de Janeiro state. The frequency of use, water contamination and a Habitat Assessment Visual Index (IAH) was also measured. The I-PURA was correlated with the frequency of use. Furthermore, the I-PURA was not correlated with IAH, showing that user perceptions are different from purely ecological aspects. This tool offers useful information for risk assessment and environmental management. Sites with a high probability of use, or observed use, that are highly contaminated should be prioritized for interventions.

Microbial Indicators and Environmental Relationships in the Umhlangane River, Durban, South Africa

The use of rivers for recreational and domestic practices makes it imperative to scrutinize the water quality circulating within surrounding communities. The complexity of biological, physical and chemical constituents in water is constantly evolving. This study evaluated various microbial and physico-chemical parameters in a polluted river system over a 12-month period. Apart from an increase in chemical pollutants, elevated levels of E. coli, total (TC) and faecal (FC) coliforms, and Shigella species could be attributed to faecal contamination entering the catchment. Canonical correspondence analysis revealed a strong relationship between FC, TC and temperature whereas moderate interactions was seen between total dissolved solids, electrical conductivity, TC and FC populations. Furthermore, close relationships between the bacterial and phage communities were also observed. The complex interactions of these physico-chemical and microbial indicators could be due to anthropogenic activities, changing climatic conditions and the excreta of infected and non-infected individuals entering the river. Assessing the complexity of aquatic ecosystems can aid in the development of novel, customizable, inexpensive water purification tools.

Abundance of Pathogenic Escherichia coli Virulence-Associated Genes in Well and Borehole Water Used for Domestic Purposes in a Peri-Urban Community of South Africa

In the absence of pipe-borne water, many people in Africa, especially in rural communities, depend on alternative water sources such as wells, boreholes and rivers for household and personal hygiene. Poor maintenance and nearby pit latrines, however, lead to microbial pollution of these sources. We evaluated the abundance of Escherichia coli and the prevalence of pathogenic E. coli virulence genes in water from wells, boreholes and a river in a South African peri-urban community. Monthly samples were collected between August 2015 and November 2016. In all, 144 water samples were analysed for E. coli using the Colilert 18 system. Virulence genes (eagg, eaeA, stx1, stx2, flichH7, ST, ipaH, ibeA) were investigated using real-time polymerase chain reaction. Mean E. coli counts ranged between 0 and 443.1 Most Probable Number (MPN)/100 mL of water sample. Overall, 99.3% of samples were positive for at least one virulence gene studied, with flicH7 being the most detected gene (81/140; 57.6%) and the stx2 gene the least detected gene (8/140; 5.7%). Both intestinal and extraintestinal pathogenic E. coli genes were detected. The detection of virulence genes in these water sources suggests the presence of potentially pathogenic E. coli strains and is a public health concern.

Evaluation of simple diffusion chlorinators for decontamination of wells in a rural settlement in Amazonia, Brazil

While the Amazon region has the world's largest reserve of fresh water, the lack of water services and water treatment, especially in non-urban regions, causes environmental and health problems. In isolated rural settlements supply is usually by shallow wells, and the quality of water is a concern for residents. These are situations where there are restricted options for water treatment. This study aimed to assess the use of simplified diffusion chlorinators as an alternative water treatment method. Bacteriological analyses were made of 100 samples of water from the wells, before and after application of the chlorinators, in the Rural Settlement of Rio Pardo, Presidente Figueiredo in the Brazilian State of Amazonas. The sources that were analyzed were considered inappropriate for consumption without prior treatment, and the use of the chlorinators eliminated all contamination by thermotolerant coliforms in the great majority of cases. Also, the method was well received by residents, because it does not leave a taste in the water, is relatively low-cost and handling is easy. We discuss the advantages and limitations of the use of this method of treatment for this social-environmental context and present suggestions for improvement and adaptation, for application of this methodology in other settlements.

Impact of seasonal variation on Escherichia coli concentrations in the riverbed sediments in the Apies River, South Africa

Many South Africans living in resource-poor settings with little or no access to pipe-borne water still rely on rivers as alternative water sources for drinking and other purposes. The poor microbial quality of such water bodies calls for appropriate monitoring. However, routine monitoring only takes into consideration the microbial quality of the water column, and does not include monitoring of the riverbed sediments for microbial pollution. This study sought to investigate the microbial quality of riverbed sediments in the Apies River, Gauteng Province, South Africa, using Escherichia coli as a faecal indicator organism and to investigate the impact of seasonal variation on its abundance. Weekly samples were collected at 10 sampling sites on the Apies River between May and August 2013 (dry season) and between January and February 2014 (wet season). E. coli was enumerated using the Colilert®-18 Quanti-Tray® 2000 system. All sites tested positive for E. coli. Wastewater treatment work effluents had the highest negative impact on the river water quality. Seasonal variations had an impact on the concentration of E. coli both in water and sediments with concentrations increasing during the wet season. A strong positive correlation was observed between temperature and the E. coli concentrations. We therefore conclude that the sediments of the Apies River are heavily polluted with faecal indicator bacteria and could also harbour other microorganisms including pathogens. The release of such pathogens into the water column as a result of the resuspension of sediments due to extreme events like floods or human activities could increase the health risk of the populations using the untreated river water for recreation and other household purposes. There is therefore an urgent need to reconsider and review the current South African guidelines for water quality monitoring to include sediments, so as to protect human health and other aquatic lives.

Quantification of human infection risk caused by rotavirus in surface waters from Córdoba, Argentina

Fecal contamination of water is a worrying problem because it is associated with the transmission of enteric pathogenic microorganisms that can cause many infectious diseases. In this study, an environmental survey was conducted to assess the level of viral contamination by viable enterovirus and rotavirus genome in two recreational rivers (Suquía and Xanaes) of Córdoba, Argentina. Quantitative microbial risk assessment (QMRA) was calculated to estimate the risk of rotavirus infection. Water sampling was carried out during a one-year period, the presence of total and fecal coliforms was determined and water samples were then concentrated for viral determination. Cell culture and indirect immunofluorescence were applied for enterovirus detection and RT-qPCR for rotavirus quantification. Coliform bacteria levels found in Suquía River often far exceeded the guideline limits for recreational waters. The Xanaes exhibited a lower level of bacterial contamination, frequently within the guideline limits. Enterovirus and rotavirus were frequently detected in the monitoring rivers (percentage of positive samples in Suquía: 78.6% enterovirus, 100% rotavirus; in Xanaes: 87.5% enterovirus, 18.7% rotavirus). Rotavirus was detected at a media concentration of 5.7×10(5) genome copies/L (gc/L) in the Suquía and 8.5×10(0)gc/L in the Xanaes. QMRA revealed high risk of rotavirus infection in the Suquía, at sampling points with acceptable and non-acceptable bacteria numbers. The Xanaes showed significantly lower health risk of rotavirus infection but it proved to be a public health hazard. The viral occurrence was not readily explained by the levels of bacteria indicators, thus viral monitoring should be included to determine microbiological water quality. These findings provide the first data of QMRA for recreational waters in Argentina and reveal the need for public awareness of the health implications of the use of the river waters.

Antimicrobial resistance and virulence signatures of Listeria and Aeromonas species recovered from treated wastewater effluent and receiving surface water in Durban, South Africa

BACKGROUND

Treated wastewater effluent has been found to contain high levels of contaminants, including disease-causing bacteria such as Listeria and Aeromonas species. The aim of this study was to evaluate the antimicrobial resistance and virulence signatures of Listeria and Aeromonas spp. recovered from treated effluents of two wastewater treatment plants and receiving rivers in Durban, South Africa.

METHODS

A total of 100 Aeromonas spp. and 78 Listeria spp. were positively identified based on biochemical tests and PCR detection of DNA region conserved in these genera. The antimicrobial resistance profiles of the isolates were determined using Kirby Bauer disc diffusion assay. The presence of important virulence genes were detected via PCR, while other virulence determinants; protease, gelatinase and haemolysin were detected using standard assays.

RESULTS

Highest resistance was observed against penicillin, erythromycin and nalidixic acid, with all 78 (100%) tested Listeria spp displaying resistance, followed by ampicillin (83.33%), trimethoprim (67.95%), nitrofurantoin (64.10%) and cephalosporin (60.26%). Among Aeromonas spp., the highest resistance (100%) was observed against ampicillin, penicillin, vancomycin, clindamycin and fusidic acid, followed by cephalosporin (82%), and erythromycin (58%), with 56% of the isolates found to be resistant to naladixic acid and trimethoprim. Among Listeria spp., 26.92% were found to contain virulence genes, with 14.10, 5.12 and 21% harbouring the actA, plcA and iap genes, respectively. Of the 100 tested Aeromonas spp., 52% harboured the aerolysin (aer) virulence associated gene, while lipase (lip) virulence associated gene was also detected in 68% of the tested Aeromonas spp.

CONCLUSIONS

The presence of these organisms in effluents samples following conventional wastewater treatment is worrisome as this could lead to major environmental and human health problems. This emphasizes the need for constant evaluation of the wastewater treatment effluents to ensure compliance to set guidelines.

A lateral flow assay for identification of Escherichia coli by ribosomal RNA hybridisation

Existing technologies for analysis of microbiological contaminants in food or clinical samples are often expensive and require laboratory settings and trained personnel. Here we present a lateral flow assay employing gold nanoparticle-oligodeoxynucleotide conjugates and four-component sandwich hybridisation for direct detection of specific sequences in bacterial 16S ribosomal RNA. Combined with rapid "one step" lysis the developed procedure allows detection of 5 × 10(4) colony forming units per mL Escherichia coli within less than 25 minutes. Several Escherichia coli strains were detected successfully, whereas non-related as well as closely related bacterial species produced no signal. The developed nucleic acid lateral flow assay is inexpensive, rapid to perform and requires no nucleic acid amplification step.

Fast coliform detection in portable microbe enrichment unit (PMEU) with Colilert(®) medium and bubbling

Laboratory strains of coliforms Escherichia coli and Klebsiella mobilis were used to artificially contaminate water samples in two different cultivation and detection systems, without and with bubble flow. Samples were collected with an automated system (ASCS). The positive coliform signal caused the color change into yellow (at 550-570nm). This signal could also be transmitted on-line to cell phones. E. coli containing samples emitted UV fluorescence at 480-560nm when activated by UV light. If cultivation was started with inocula varying from 10,000 to 1cfu/ml, the positive detection was obtained between 2 and 18h, respectively, in Colilert medium using Coline PMEU device without gas bubbling. Accordingly, a single K. mobilis cell produced detectable growth in 18h. Various clinical E. coli strains were compared to each other with equal inoculum sizes, and they showed slight variations in the initiation and speed of growth. The gas bubble flow in PMEU Spectrion promoted the mixing and interaction of bacteria and indicator media and speeded the onset of growth. Carbon dioxide also accelerated bacterial growth. In the presence of vancomycin, the onset of E. coli culture growth was speeded up by the volatile outlet flow from previous cultures. In the last cultivation syringe in a series of five, the lag phase disappeared and the growth of the inoculum continued without major interruption.

IN CONCLUSION

the stimulation of the cultures by the gas flow turned out to be a useful means for improving the detection of indicator bacteria. It could also be used in combination with antibiotic selection in the broth medium.