Depth and Well Type Related to Groundwater Microbiological Contamination

Risk factors for Cryptosporidium contamination in Minnesota public supply wells

In a recent monitoring study of Minnesota's public supply wells, Cryptosporidium was commonly detected with 40% of the wells having at least one detection. Risk factors for Cryptosporidium occurrence in drinking water supply wells, beyond surface water influence, remain poorly understood. To address this gap, physical and chemical factors were assessed as potential predictors of Cryptosporidium occurrence in 135 public supply wells in Minnesota. Univariable analysis, regression techniques, and classification trees were used to analyze the data. Many variables were identified as significant risk factors in univariable analysis and several remained significant throughout the succeeding analysis techniques. These factors fell into general categories of well use and construction, aquifer characteristics, and connectedness to the land surface, well capture zones, and land use therein, existence of potential contaminant sources within 200-feet of the well, and variability in the chemical and isotopic parameters measured during the study. These risk categories, and the specific variables and threshold values we have identified, can help guide future research on factors influencing Cryptosporidium contamination of wells and can be used by environmental health programs to develop risk-based sampling plans and design interventions that reduce associated health risks.

The antimicrobial resistance profiles of Escherichia coli and Pseudomonas aeruginosa isolated from private groundwater wells in the Republic of Ireland

The role of the natural environment in the dissemination of antimicrobial resistant bacteria has been increasingly recognised in the literature. However, knowledge surrounding the critical factors and mechanisms mediating their occurrence is still limited, particularly in relatively 'pristine' groundwater environments. In the Republic of Ireland (RoI), a country characterised by high groundwater reliance, household-based (unregulated) wells provide drinking water to 11% of the population. These private wells are generally located in rural areas, where the risk of microbiological contamination is high due to intensive agricultural practices and high reliance on domestic wastewater treatment systems; both of which are also potential sources of antimicrobials and antimicrobial resistant bacteria. Accordingly, the current research sought to elucidate current rates of antimicrobial resistant bacteria and the principal factors associated with their presence in private wells in the RoI. A total of 250 samples (from 132 wells nationwide) were assessed for the presence of faecal (Escherichia coli) and environmental (Pseudomonas aeruginosa) bacteria, with single isolates from each contaminated sample tested phenotypically against 18 and 9 antimicrobials, respectively. Findings show that while 16.7% of E. coli (n = 8/48) were categorically resistant to ≥1 antimicrobial, with a further 79.2% classified as intermediately resistant, no categorical resistance was found among P. aeruginosa isolates (n = 0/6), with just one intermediately resistant isolate detected. Multivariate regression modelling indicates significantly higher odds of resistant E. coli detection in concurrence with elevated cattle density (OR = 1.028, p = 0.032), aligning with findings of highest resistance rates to veterinary antimicrobials (e.g., streptomycin = 14.6%, tetracycline = 12.5%, and ampicillin = 12.5%). Multivariate model results also suggest overland flow culminating in direct wellhead ingress as a primary ingress mechanism for resistant E. coli. Study findings may inform groundwater source protection initiatives and antimicrobial resistance surveillance moving forward.

Candida species contamination in drinking groundwater from residence wells in three municipalities of midwestern Brazil and the potential human health risks

Groundwater represents one of the largest safe drinking water sources worldwide; however, it has been threatened by increased human activities in recent years. Candida species express virulence factors that contribute to the establishment and worsening of infections, although little is known about the virulence profiles of these species in potable groundwater. The aim of this study was to detect the presence of yeasts in groundwater from residential wells and to evaluate the antifungal susceptibility profile, hydrolytic enzyme production, adhesion capacity, and biofilm formation of Candida spp. Fifty yeasts representing nine genera were isolated: Candida (48%), Meyerozyma (20%), Pichia (8%), Exophiala (8%), Clavispora (4%), Kodamaea (4%), Rhodotorula (4%), Hanseniaspora (2%), and Kazachstania (2%). Candida parapsilosis was the most commonly isolated species, and approximately 29% of the Candida isolates were resistant to at least one azole. All Candida isolates were able to produce hydrolytic enzymes and adhere to polystyrene, and most were classified as hydrophobic. Candida spp. can establish and form biofilms when cultivated in different media such as Sabouraud broth, water, and calcium hypochlorite. The use of contaminated groundwater for human consumption represents a possible route for the transmission of clinically relevant yeasts that can cause fungal infections, especially in immunocompromised individuals. Therefore, it is important to evaluate and establish effective measures for groundwater treatment to ensure the quality and safety for consumption.

Prevalence, diversity of diarrhoeagenic Escherichia coli and associated risk factors in well water in Ile-Ife, Southwestern Nigeria

BACKGROUND

Diarrhoeagenic Escherichia coli (DEC) strains are common causes of morbidity and mortality worldwide. Waterborne DEC could pose a health risk to humans through domestic use of contaminated water. However, epidemiological studies on DEC in well water are scarce in Nigeria. This study determined the prevalence, diversity and factors associated with the presence of DEC in well water in Ile-Ife, southwestern Nigeria.

METHODS

We assessed 143 wells for safety and a questionnaire was administered. Contaminating isolates were identified as E. coli by amplifying their 16S rRNA gene. Five diarrhoeagenic E. coli pathotypes were sought using multiplex polymerase chain reaction (PCR). (GTG)5 repetitive PCR and Shannon diversity index were used to determine isolates diversity. Multivariate analysis was used to reveal the factors associated with the presence of DEC in  well water.

RESULTS

Fifty-six (39.2%) wells were contaminated by diarrhoeagenic E. coli. Wells with dirty platforms, undercut by erosion and sited near septic tanks significantly harboured DEC (p <  0.05). There was a preponderance of Shiga-toxin producing E. coli among the isolates with 10 (17.9%) wells contaminated by multiple DEC. The DEC isolates showed 45 unique fingerprints and were divided into six clades, with an overall diversity index of 18.87.

DISCUSSION

The presence of DEC in well water highlights the risk to human health associated with the use of untreated water. There was a high degree of genetic diversity among the isolates implying multiple sources of contamination. There is a need for periodic sanitation and inspection of wells for cracks to prevent seepages and possible outbreaks of waterborne diseases.

Histopathologic Lesions in Bivalve Mollusks Found in Portugal: Etiology and Risk Factors

Bivalve mollusks are an important resource due to their socioeconomic value and to the historical and genetic value of some species. Two nationally important oyster species-Portuguese oyster (Crassostrea angulata) and Japanese oyster (Crassostrea gigas) from distinctive areas in Portugal were studied to evaluate their sanitary status. Oysters were sampled from four different sites in Portugal. Oysters collected from Japanese oyster populations were cultivated in a strong ocean-influenced environment and Portuguese oyster populations were cultivated in wild-beds. The histopathological examination of both oyster species revealed the presence of parasites in gills, mantle epithelium, digestive gland tubules and connective tissue, with a moderate prevalence. In both populations was observed hemocytosis in the connective tissue, edema and metaplasia in the digestive gland and tissues necrosis. In wild populations from Sado and Mira estuaries the prevalence of mud blisters and gill lesions were higher than from populations produced on 0.50 m tables from mudflats. Biosecurity measures and diagnostic techniques are fundamental to control pathogenic agents, including the identification of pathogens at an early stage in their life cycles. This will prevent diseases and improve pathogen reduction on transport of animals from different countries and regions to new production areas to avoid the transmission of diseases.

Faecal contamination of groundwater self-supply in low- and middle income countries: Systematic review and meta-analysis

Self-supply is a ubiquitous response by households to the public water supply inadequacies found worldwide. Self-supply is invested in and managed by an individual household, accessible on-premises and unregulated. Vulnerability to faecal contamination is a concern due to reliance on low-cost technologies and shallow groundwater. This review aims to evaluate the evidence base on the safety of groundwater self-supply in low- and middle income countries in relation to faecal contamination. Differences in microbial water quality between source types, settings, countries and ownership were investigated. A search of peer-reviewed studies in low- and middle income countries was conducted in online databases, including PubMed, Web of Science, ProQuest and Environmental Complete. Studies were included if they had sufficient detail about the water samples to be related to groundwater self-supply, contained extractable data on faecal indicator bacteria (FIB) including thermotolerant coliform or Escherichia coli and were published in English between 1990 and April 2020. A total of 30 studies were included, resulting in 100 datasets and 26,981 water samples across the studies. FIB were present in 36% self-supply samples. The odds of FIB being detected was significantly higher for unimproved sources (OR=8.19, 95% CI [4.04-16.59], p<0.001) and for sources in low income countries (OR=3.85, 95% CI [1.85-7.69], p<0.001). Self-supply was significantly more likely to be contaminated than piped supply (OR=3.45, 95% CI [1.52-7.82], p=0.003). However, water quality was highly heterogeneous (I²=90.9%). Egger's test found no evidence of small study publication bias for self-supply compared to public supply. No evidence of bias due to lack of randomization or season was found, but study design and quality could potentially bias the results. To achieve Sustainable Development Goal 6.1 on safe drinking water for all, more attention is needed from governments to engage with self-supply and formulate balanced policy responses.

Molecular detection of opportunistic pathogens and insights into microbial diversity in private well water and premise plumbing

Private well water systems in rural areas that are improperly maintained will result in poor drinking water quality, loss of water supply, and pose human health risk. The purpose of this study was to investigate the occurrence of fecal indicator bacteria (FIB) and opportunistic pathogens in private well water in rural areas surrounding New Orleans, Louisiana. Our results confirmed the ubiquitous nature of Legionella (86.7%) and mycobacteria (68.1%) in private well water in the study area, with gene concentration ranged from 0.60 to 5.53 and 0.67 to 5.95 Log₁₀ of GC/100 mL, respectively. Naegleria fowleri target sequence was detected in 16.8% and Escherichia coli was detected in 43.4% of the water samples. Total coliform, as well as Legionella and mycobacteria genetic markers' concentrations were significantly reduced by 3-minute flushing. Next-generation sequencing (NGS) data indicated that the abundance of bacterial species was significantly increased in water collected in kitchens compared with samples from wells directly. This study provided integrated knowledge on the persistence of pathogenic organisms in private well water. Further study is needed to explore the presence of clinical species of those opportunistic pathogens in private well water systems to elucidate the health risk.

Groundwater resources as a global reservoir for antimicrobial-resistant bacteria

Antimicrobial resistance represents one of our most significant global health threats, with increasing incidences noted in both clinical and environmental settings. As such, identifying and understanding the sources and pathways for antimicrobial-resistant bacteria (ARB) is critical. The current study presents the first systematic review and pooled analysis of ARB occurrence in global groundwater supplies, which are used as primary drinking water sources by 2.2 billion people worldwide and are recurrently linked to significant outbreaks of infection. Seventy peer-reviewed studies were identified and included; findings reveal that 80.2% ± 29.0 and 57.2% ± 36.8 of aggregated groundwater isolates were resistant to ≥1 and ≥3 antimicrobials, respectively. Where bacteria were present, ARB were identified in 76.9% ± 33.7 of individual wells and springs. Our results leave little doubt that groundwater represents a major global reservoir for ARB, however significant research is required to establish environmental determinants and mechanisms mediating their occurrence.

Effects of age, sex, medication, and environmental conditions on genetic alterations in oral mucosa cells

In the present study, we evaluated the effects of biological factors, lifestyle factors, and environmental conditions on the induction of DNA damage in exfoliated cells of the oral mucosa. Age, sex, medication use, and environmental conditions were analyzed in individuals residing in the cities of Caarapó and Itaporã. The individuals were assessed by a questionnaire, and oral mucosa cells were collected and subjected to mutagenicity analysis. We observed no statistical differences in DNA damage related to sex. However, the mutagenic effect was found to be proportional to age, with higher frequencies of DNA damage observed in individuals between the ages of 46 and 65 years. In addition, higher frequencies of DNA damage were found in individuals who continuously used medication and for prolonged periods, and greater DNA damage was observed in individuals who used antihypertensive drugs than those who took antidepressants. In terms of environmental conditions, Caarapó residents had a significantly higher frequency of DNA damage than that of residents from Itaporã. Based on the analysis of land use and occupation, this result can be attributed to the smaller fraction of forest fragments and the higher proportion of buildings in Caarapó than Itaporã. We concluded that age, continued medication use, and environmental conditions can lead to greater DNA damage.

Groundwater Nitrate Contamination Integrated Modeling for Climate and Water Resources Scenarios: The Case of Lake Karla Over-Exploited Aquifer

Groundwater quantity and quality degradation by agricultural practices is recorded as one of the most critical issues worldwide. This is explained by the fact that groundwater is an important component of the hydrological cycle, since it is a source of natural enrichment for rivers, lakes, and wetlands and constitutes the main source of potable water. The need of aquifers simulation, taking into account water resources components at watershed level, is imperative for the choice of appropriate restoration management practices. An integrated water resources modeling approach, using hydrological modeling tools, is presented for assessing the nitrate fate and transport on an over-exploited aquifer with intensive and extensive agricultural activity under various operational strategies and future climate change scenarios. The results indicate that climate change affects nitrates concentration in groundwater, which is likely to be increased due to the depletion of the groundwater table and the decrease of groundwater enrichment in the future water balance. Application of operational agricultural management practices with the construction and use of water storage infrastructure tend to compensate the groundwater resources degradation due to climate change impacts.