Fungal Contaminants in Drinking Water Regulation? A Tale of Ecology, Exposure, Purification and Clinical Relevance

Yeast Biodiversity of Karst Waters: Interest of Four Culture Media and an Improved MALDI-TOF MS Database

Karst aquifers are a significant source of drinking water and highly vulnerable to pollution and microbial contamination. Microbiological regulations for the quality of drinking water mostly focus on bacterial levels and lack guidance concerning fungal contamination. Moreover, there is no standardised microbial analysis methodology for identifying fungi in water. Our main objective was to establish the most effective culture and identification methodology to examine yeast diversity in karst waters. We assessed the comparative efficacy of four culture media (CHROMagar Candida, dichloran glycerol 18% [DG18], dichloran rose Bengal chloramphenicol [DRBC], and SYMPHONY agar) for yeast isolation from karst water samples. Furthermore, we investigated the comprehensiveness of databases used in MALDI-TOF mass spectrometry (MALDI-TOF MS) for identifying environmental yeast species. In total, we analysed 162 water samples, allowing the identification of 2479 yeast isolates. We demonstrate that a combination of four culture media, each with distinct specifications, more efficiently covers a wide range of yeast species in karst water than a combination of only two or three. Supplementation of a MALDI-TOF MS database is also critical for analysing environmental microbial samples and improved the identification of yeast biodiversity. This study is an initial step towards standardising the analysis of fungal biodiversity in karst waters, enabling a better understanding of the significance of this environmental reservoir in relation to public health.

Drug-Resistant Aspergillus spp.: A Literature Review of Its Resistance Mechanisms and Its Prevalence in Europe

Infections due to the Aspergillus species constitute an important challenge for human health. Invasive aspergillosis represents a life-threatening disease, mostly in patients with immune defects. Drugs used for fungal infections comprise amphotericin B, triazoles, and echinocandins. However, in the last decade, an increased emergence of azole-resistant Aspergillus strains has been reported, principally belonging to Aspergillus fumigatus species. Therefore, both the early diagnosis of aspergillosis and its epidemiological surveillance are very important to establish the correct antifungal therapy and to ensure a successful patient outcome. In this paper, a literature review is performed to analyze the prevalence of Aspergillus antifungal resistance in European countries. Amphotericin B resistance is observed in 2.6% and 10.8% of Aspergillus fumigatus isolates in Denmark and Greece, respectively. A prevalence of 84% of amphotericin B-resistant Aspergillus flavus isolates is reported in France, followed by 49.4%, 35.1%, 21.7%, and 20% in Spain, Portugal, Greece, and amphotericin B resistance of Aspergillus niger isolates is observed in Greece and Belgium with a prevalence of 75% and 12.8%, respectively. The prevalence of triazole resistance of Aspergillus fumigatus isolates, the most studied mold obtained from the included studies, is 0.3% in Austria, 1% in Greece, 1.2% in Switzerland, 2.1% in France, 3.9% in Portugal, 4.9% in Italy, 5.3% in Germany, 6.1% in Denmark, 7.4% in Spain, 8.3% in Belgium, 11% in the Netherlands, and 13.2% in the United Kingdom. The mechanism of resistance is mainly driven by the TR34/L98H mutation. In Europe, no in vivo resistance is reported for echinocandins. Future studies are needed to implement the knowledge on the spread of drug-resistant Aspergillus spp. with the aim of defining optimal treatment strategies.

Outbreaks of Fungal Infections in Hospitals: Epidemiology, Detection, and Management

Nosocomial clusters of fungal infections, whilst uncommon, cannot be predicted and are associated with significant morbidity and mortality. Here, we review reports of nosocomial outbreaks of invasive fungal disease to glean insight into their epidemiology, risks for infection, methods employed in outbreak detection including genomic testing to confirm the outbreak, and approaches to clinical and infection control management. Both yeasts and filamentous fungi cause outbreaks, with each having general and specific risks. The early detection and confirmation of the outbreak are essential for diagnosis, treatment of affected patients, and termination of the outbreak. Environmental sampling, including the air in mould outbreaks, for the pathogen may be indicated. The genetic analysis of epidemiologically linked isolates is strongly recommended through a sufficiently discriminatory approach such as whole genome sequencing or a method that is acceptably discriminatory for that pathogen. An analysis of both linked isolates and epidemiologically unrelated strains is required to enable genetic similarity comparisons. The management of the outbreak encompasses input from a multi-disciplinary team with epidemiological investigation and infection control measures, including screening for additional cases, patient cohorting, and strict hygiene and cleaning procedures. Automated methods for fungal infection surveillance would greatly aid earlier outbreak detection and should be a focus of research.

Characterization of microbial communities in seven wetlands with different anthropogenic burden using Next Generation Sequencing in Bogotá, Colombia

Wetlands represent key ecosystems due to their remarkable biodiversity, ecological functions and multiple ecosystem services provided. In Colombia, there are 31,702 wetlands, 13 of which are in Bogotá, capital of the country. Despite the fundamental socioecological support of these aquatic ecosystems, a tremendous loss and degradation of these ecosystems has been observed due to anthropogenic perturbations. Therefore, the aim of this study was to describe the status of seven Bogotá wetlands with variable anthropogenic interventions by measuring organoleptic, physicochemical, and microbiological parameters, using commercial kits, highly sensitive equipment, and next-generation sequencing of the 16S- and 18S-rRNA genes. Our findings describe the status of seven wetlands with different anthropogenic burden in Bogotá-Colombia where physicochemical and microbiology signals of contamination were observed. Additionally, some profiles in the composition of the microbial communities, together with certain physicochemical characteristics, may represent an insight into the environmental dynamics, where Beta Proteobacteria such as Malikia represent a potential keystone in aquatic ecosystems impacted by wastewater effluent discharges; the presence of nitrates and phosphates explain the abundance of bacteria capable of oxidizing these compounds, such as Polynucleobacter. Moreover, the presence of specific prokaryotic and eukaryotic organisms, such as Clostridium, Cryptococcus, Candida, and Naegleria, reported in one or more of the wetlands assessed here, could represent a possible pathogenic risk for human and animal health. This study performed a complete evaluation of seven Bogotá wetlands with different anthropogenic impacts for the first time, and our findings emphasize the importance of maintaining continuous monitoring of these water bodies given their remarkable ecological importance and potential spill-over of several pathogens to humans and animals.

Culturable mycobiota of drinking water in Göteborg (Sweden) in comparison to Ljubljana (Slovenia) with implications on human health

The European Union currently has no specific regulations on fungi in water. The only country where fungi are listed as the parameter is Sweden, with the maximal number of 100 CFU per 100 mL. The present study thus compared culturable mycobiota from Swedish drinking water with Slovenian, which has no specific requirements for fungi. Fungi were isolated with up to 38 CFU/L from 75% of Swedish samples. The most common were the genera Varicosporellopsis (27.3%), Paracremonium (14.5%), and black yeasts Cadophora, Cyphellophora, and Exophiala (18.2%). Using the same sampling and isolation methods, 90% of tap water samples in Slovenia were positive for fungi, with Aspergillus spp. (46%), Aureobasidium melanogenum (36%), and Exophiala spp. (24%) being the most common. The observed differences between countries are likely the consequence of geographical location, the use of different raw water sources, and water treatment methods. However, the core species and emerging fungi Aspergillus fumigatus, Candida parapsilosis sensu stricto, Exophiala phaeomuriformis, Bisifusarium dimerum, and Rhodotorula mucilaginosa were isolated in both studies. These findings point out the relevance of tracking the presence of emerging fungi with known effects on health in drinking water and encourage further studies on their transmission from raw water sources to the end-users.

Antibiofilm activity of LAE (ethyl lauroyl arginate) against food-borne fungi and its application in polystyrene surface coating

Several filamentous fungi species as Fusarium oxysporum or Cladosporium sp. can form biofilms by themselves or by participating in polymicrobial biofilms with bacteria. However, despite the high impact of biofilm on the food industry and the high efforts done to control biofilm produced by bacteria in the food area, there has been little study of strategies to control fungal biofilm in this area. In this study, the antibiofilm activity of the safe antimicrobial compound ethyl lauroyl arginate (LAE) was investigated against food spoilage fungi (Cladosporium cladosporioides, Aspergillus ochraceus, Penicillium italicum, Botrytis cynerea and Fusarium oxyspoum). Finally, the efficacy of a varnish-based coating incorporating LAE and coated onto polystyrene microtiter plates has been evaluated as a strategy to reduce fungal biofilm formation. The results of the 2,3-bis-(2-metoxi-4-nitro-5-sulfofenil)-2H-tetrazoilo-5-carboxanilida (XTT) assay, which measure the biofilm metabolic activity of moulds, demonstrated that LAE reduced significantly the formation of fungal biofilm at concentrations from 6 to 25 mg/L. This reduction was confirmed by the micrographs obtained by scanning electronic microscopy (SEM). In addition, LAE also showed antifungal activity against established biofilms. Particularly, it reduced their metabolic activity and viability at concentrations from 6 to 25 mg/L according to results obtained in the XTT assay and observations made by confocal laser scanning microscopy (CLSM). Finally, active coating incorporating from 2% of LAE proved to reduce significantly the biofilm formation in C. cladosporioides, B. cynerea and F. oxyspoum according to the results obtained in the XTT assay. However, the released studies indicated that the retention of LAE in the coating should be improved to prolong their activity.

Pulsed ultraviolet (PUV) disinfection of artificially contaminated seawater seeded with high levels of pathogen disease indicators as an alternative for the shellfish industry depuration systems

The increase in pathogen levels in seawater threatens the safety of entire aquatic ecosystems. Foodborne pathogens can potentially accumulate in shellfish, especially in filter feeders such as bivalves, requiring an efficient depuration process before consumption. Alternative approaches to promote a cost-efficient purge at depuration plants are urgently needed. A small prototype pulsed ultraviolet (PUV) light recirculation system was designed, and its depuration potential was tested in a seawater matrix artificially contaminated with high levels of microbial pathogens Escherichia coli, Staphylococcus aureus, Salmonella typhimurium, Bacillus cereus and Candida albicans. The analysis of treatment parameters including voltage, number of pulses and duration of treatment was performed to ensure the highest reduction in contaminant levels. Optimal PUV disinfection was attained at 60 pulses/min at 1 kV for 10 min (a UV output of 12.9 J/cm²). All reductions were statistically significant, and the greatest was observed for S. aureus (5.63 log₁₀), followed by C. albicans (5.15 log₁₀), S. typhimurium (5 log₁₀), B. cereus (4.59 log₁₀) and E. coli (4.55 log₁₀). PUV treatment disrupted the pathogen DNA with the result that S. aureus, C. albicans and S. typhimurium were not detectable by PCR. Regulations were reviewed to address the applicability of PUV treatment as a promising alternative to assist in the reduction of microbial pathogens at depuration plants due to its high efficiency, short treatment period, high UV dose and recirculation system as currently employed in shellfish depuration plants.

Occurrence of fungal spores in drinking water: A review of pathogenicity, odor, chlorine resistance and control strategies

Fungi in drinking water have been long neglected due to the lack of convenient analysis methods, widely accepted regulations and efficient control strategies. However, in the last few decades, fungi in drinking water have been widely recognized as opportunity pathogens that cause serious damage to the health of immune-compromised individuals. In drinking water treatment plants, fungal spores are more resistant to chlorine disinfection than bacteria and viruses, which can regrow in drinking water distribution systems and subsequently pose health threats to water consumers. In addition, fungi in drinking water may represent an ignored source of taste and odor (T&O). This review identified 74 genera of fungi isolated from drinking water and presented their detailed taxonomy, sources and biomass levels in drinking water systems. The typical pathways of exposure of water-borne fungi and the main effects on human health are clarified. The fungi producing T&O compounds and their products are summarized. Data on free chlorine or monochloramine inactivation of fungal spores and other pathogens are compared. At the first time, we suggested four chlorine-resistant mechanisms including aggregation to tolerate chlorine, strong cell walls, cellular responses to oxidative stress and antioxidation of melanin, which are instructive for the future fungi control attempts. Finally, the inactivation performance of fungal spores by various technologies are comprehensively analyzed. The purpose of this study is to provide an overview of fungi distribution and risks in drinking water, provide insight into the chlorine resistance mechanisms of fungal spores and propose approaches for the control of fungi in drinking water.

Endotoxin as a Marker for Water Quality

BACKGROUND

Water quality testing is vital to protect human health. Current testing relies mainly on culture-based detection of faecal indicator organisms such as Escherichia coli (E.coli). However, bacterial cultures are a slow process, taking 24-48 h and requiring specialised laboratories and trained personnel. Access to such laboratories is often sparse in developing countries and there are many fatalities deriving from poor water quality. Endotoxin is a molecular component of Gram-negative bacterial cell walls and can be used to detect their presence in drinking water.

METHOD

The current study used a novel assay (BacterisK) to rapidly detect endotoxin in various water samples and correlate the results with E. coli content measured by culture methods. The data generated by the BacterisK assay are presented as an 'endotoxin risk' (ER).

RESULTS

The ER values correlate with E. coli and thus endotoxin can be used as a marker of faecal contamination in water. Moreover, the BacterisK assay provides data in near real-time and can be used in situ allowing water quality testing at different spatial and temporal locations.

CONCLUSION

We suggest that BacterisK can be used as a convenient risk assessment tool to assess water quality where results are required quickly or access to laboratories is lacking.

Fungal signatures of oral disease reflect environmental degradation in a facultative avian scavenger

Degradation of natural ecosystems increases the risk of infections in wildlife due to microbiota dysbiosis. However, little is known about its influence on the development of fungal communities in predators and facultative avian scavengers. We evaluated the incidence of oral disease in wild nestling black kites (Milvus migrans) under contrasting environmental degradation conditions, and explored their oral fungal patterns using molecular methods and multivariate analysis. Oral lesions were found in 36.8% of the 38 nestlings examined in an anthropogenically altered habitat (southeastern Madrid, Spain), but in none of the 105 nestlings examined in a well-conserved natural area (Doñana National Park, Spain). In a subsample of 48 black kites, the composition of the oral fungal community differed among symptomatic nestlings from Madrid (SM) and asymptomatic nestlings from Madrid (AM) and Doñana (AD). Opportunistic fungal pathogens (e.g., Fusarium incarnatum-equiseti species complex, Mucor spp., Rhizopus oryzae) were more prevalent in SM and AM than in AD. Hierarchical clustering and principal component analyses revealed that fungal patterns were distinct between both study areas, and that anthropogenic and natural environmental factors had a greater impact on them than oral disease. Fungal signatures associated with anthropogenic and natural stresses harbored some taxa that could be used to flag oral infection (F. incarnatum-equiseti species complex and Alternaria), indicate environmental degradation (Alternaria) or provide protective benefits in degraded environments (Trichoderma, Epicoccum nigrum and Sordaria). Co-occurrence associations between potentially beneficial and pathogenic fungi were typical of AM and AD, hinting at a possible role in host health. This study shows that early-life exposure to highly degraded environments induces a shift towards a higher prevalence of pathogenic species in the oral cavity of black kites, favoring oral disease. Furthermore, our findings suggest potential ecological applications of the monitoring of oral mycobiome as a bioindication of oral disease and environmental degradation.

The protective role and mechanism of melanin for Aspergillus niger and Aspergillus flavus against chlorine-based disinfectants

Melanin is a critical component of fungal cell wall which protect fungi from adverse environmental tress. However, the role of melanin for fungi during the disinfection with chlorine-based disinfectants has not been elucidated. The results showed that the inactivation rate constants of Aspergillus niger with chlorine and chlorine dioxide decreased from 0.08 to 2.10 min^-1 to 0 after addition of 0.32 mg/L melanin. The results indicated addition of extracted fungal melanin inhibited the inactivation efficiency of chlorine and chlorine dioxide. In contrast, the k of Aspergillus niger after inactivation with monochloramine ranged from 1.50 to 1.78 min^-1 after addition of melanin which indicated effect of melanin on the inactivation efficiency of monochloramine was negligible. In addition, the extracted fungal melanin exhibited high reactivity with chlorine and chlorine dioxide but very low reactivity with monochloramine. The different inactivation mechanisms of chlorine-based disinfectants and different reactivity of melanin with chlorine-based disinfectants led to the different protective mechanism of melanin for A. niger and A. flavus spores against disinfection with chlorine-based disinfectants. The chlorine and chlorine dioxide appeared to react with functional groups of melanin in cell wall of spores, so sacrificial reactions between melanin and disinfectants decreased the available disinfectants and limited the diffusion of disinfectants to the reactive site on cell membrane, which led to the decrease of the disinfection efficiency for chlorine and chlorine dioxide. The monochloramine could penetrate into cell and damage DNA without the effect of melanin due to its strong penetration and low reactivity with melanin. Our results systematically demonstrate the protective roles of melanin on the fungal spores against chlorine-based disinfectants and the underlying mechanisms in resisting the environmental stress caused by chlorine-based disinfectants, which provides important implications for the control of fungi, especially for fungi producing melanin.

Differentiation of DNA or membrane damage of the cells in disinfection by flow cytometry

Recently, the viabilities changes of fungal spores in the water supply system during different disinfection processes have been revealed. SYBR Green I (SG), a nucleic acid stain, its fluorescence intensity is correlated with the amount of double-stranded DNA. This study established a new method through successive SG-SG-PI staining (PI: Propidium Iodide) with flow cytometry (FCM). It could successfully distinguish DNA damage and membrane damage of fungal spores, clearly elucidating the intrinsic disinfection mechanism during the chemical disinfection. This method was briefly described as follows: firstly, (1) the fungal spores were stained with SG and washed by centrifugation; and then, (2) the washed spores were treated with disinfectants and terminated; after that, (3) the disinfected spores were re-stained with SG and analyzed by FCM; finally, (4) the SG re-stained spores were stained with PI and analyzed by FCM. The percentages of spores with DNA damage and membrane damage were determined by the fluorescence intensity obtained from steps (3) and (4), respectively. The repeatability and applicability of this developed method were confirmed. It was further applied to explore the inactivation mechanism during chlorine-based disinfection, and results demonstrated that chloramine attacked the DNA more seriously than the membrane, while chlorine and chlorine dioxide worked in a reverse way.

Cultivable Skin Mycobiota of Healthy and Diseased Blind Cave Salamander (Proteus anguinus)

Proteus anguinus is a neotenic cave salamander, endemic to the Dinaric Karst and a symbol of world natural heritage. It is classified as “vulnerable” by the International Union for Conservation of Nature (IUCN) and is one of the EU priority species in need of strict protection. Due to inaccessibility of their natural underground habitat, scientific studies of the olm have been conducted mainly in captivity, where the amphibians are particularly susceptible to opportunistic microbial infections. In this report, we focused on the diversity of cultivable commensal fungi isolated from the skin of asymptomatic and symptomatic animals obtained from nature (20 specimens) and captivity (22 specimens), as well as from underground water of two karstic caves by direct water filtration and by exposure of keratin-based microbial baits and subsequent isolation from them. In total 244 fungal isolates were recovered from the animals and additional 153 isolates were obtained from water samples. Together, these isolates represented 87 genera and 166 species. Symptomatic animals were colonized by a variety of fungal species, most of them represented by a single isolate, including genera known for their involvement in chromomycosis, phaeohyphomycosis and zygomycosis in amphibians: Acremonium, Aspergillus, Cladosporium, Exophiala, Fusarium, Mucor, Ochroconis, Phialophora and Penicillium. One symptomatic specimen sampled from nature was infected by the oomycete Saprolegnia parasitica, the known causative agent of saprolegniosis. This is the first comprehensive report on cultivable skin mycobiome of this unique amphibian in nature and in captivity, with an emphasis on potentially pathogenic fungi and oomycetes.

Microbial Community Structure and Diversity in Drinking Water Supply, Distribution Systems as well as Household Point of Use Sites in Addis Ababa City, Ethiopia

Understanding ecology of microbiomes in drinking water distribution systems is the most important notion in delivering safe drinking water. Drinking water distribution systems harbor various microbiota despite efforts made in improving water infrastructures in the water industry, especially, in developing countries. Intermittent water supply, long time of water storage, low water pressure, and contaminated source water are among many of the factors responsible for poor drinking water quality affecting health of people. The aim of this study was to explore microbial diversity and structure in water samples collected from source water, treated water, reservoirs, and household points of use locations (taps). High-throughput Illumina sequencing technology was employed by targeting the V4 region of the 16S rRNA gene and the V1-V3 region of the 18S rRNA gene to analyze the microbial community structure. Proteobacteria followed by Firmicutes, Bacteroidetes, and Actinobacteria were the core dominating taxa. Gammaproteobacteria was also dominant among other proteobacterial classes across all sampling points. Opportunistic bacterial genera such as Pseudomonas, Legionella, Klebsiella, Escherichia, and Actinobacteria, as well as eukaryotic microbes like Cryptosporidium, Hartmannella, Acanthamoeba, Aspergillus, and Candida were also abundant taxa found along the distribution systems. The shift in microbial community structure from source to point of use locations was influenced by basic factors such as residual chlorine, intermittent water supply, and long-time storage at the household. The complex microbiota detected in different sampling sites in this study brings drinking water quality problem which further causes significant health problems to both human and animal health. Treatment ineffectiveness, disinfection inefficiency, poor maintenance actions, leakage of sewage, and other domestic wastes are few among many other factors responsible for degraded drinking water quality in this study putting health at high risk. Findings of this research provide important and baseline information to understand the microbial profiles of drinking water along source water and distribution systems. Moreover, knowing the microbial profile will help to design proper water quality assurance approaches.

Inactivation and subsequent reactivation of Aspergillus species by the combination of UV and monochloramine: Comparisons with UV/chlorine

Ultraviolet (UV)/monochloramine (NH₂Cl) as an advanced oxidation process was firstly applied for Aspergillus spores inactivation. This study aims to: i) clarify the inactivation and photoreactivation characteristics of UV/NH₂Cl process, ii) compared with UV/Cl₂ in inactivation efficiency, photoreactivation and energy consumption. The results illustrated that UV/NH₂Cl showed better inactivation efficiency than that of UV alone and UV/Cl₂, and could effectively control the photoreactivation. For instance, the inactivation rates for Aspergillus flavus, Aspergillus niger and Aspergillus fumigatus in the processes of UV/NH₂Cl (2.0 mg/L) was 0.034, 0.030 and 0.061 cm²/mJ, respectively, which were higher than that of UV alone (0.027, 0.026 and 0.024 cm²/mJ) and UV/Cl₂ (0.023, 0.026 and 0.031 cm²/mJ). However, there was no synergistic effect for Aspergillus flavus and Aspergillus fumigatus. As for Aspergillus niger, the best synergistic effect can reach 1.86-log₁₀. This may be due to their different resistance to disinfectants, which were related to the size, an outer layer of rodlets (hydrophobins) and pigments. After UV/NH₂Cl inactivation, the degree of cell membrane damage and intracellular reactive oxygen species were higher than that of UV alone. UV/NH₂Cl had the advantages of high inactivation efficiency and inhibition of photoreactivation, which provides a new entry point for the disinfection of waterborne fungi.

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.

Effective inactivation of fungal spores by the combined UV/PAA: Synergistic effect and mechanisms

Peracetic acid (PAA) can effectively inactivate fungi in water, while may pose a potential risk of regrowth after disinfection. The inactivation kinetic and mechanism of fungal spores by combined UV and PAA (UV/PAA) was investigated in this study. The results showed that synergistic factor of the inactivation of A. niger and A. flavus was 1.44 and 1.37, which indicated significant synergistic effect of UV/PAA. The k of A. niger and A. flavus was similar at pH 5.0 and 7.0, while decreased 60.00% and 39.13% at pH 9.0 compared with that at pH 7.0. The effect of HA concentration on the inactivation efficiency of fungal spores by UV/PAA was negative, while the effect of PAA concentration was positive. The membrane permeabilized cell of A. niger and A. flavus caused by UV/PAA was 17.0% and 31.7%, which was higher than that caused by PAA and UV alone. The changes of morphology of fungal spores and the leakage of intracellular material indicated that the damage of cell structure caused by UV/PAA system was more serious than that of UV or PAA alone. In addition, the four parts that contributed in UV/PAA system was in the following order: UV > radical > PAA > synergistic effect. The inactivation efficiency of combined UV and chlorine (UV/Cl₂) was higher than that of UV/PAA. Furthermore, the typical order of the inactivation efficiency in different matrix was: phosphate buffer solution > surface water > secondary effluent. The regrowth potential of fungal spores after UV/PAA treatment was significantly lower than that by PAA alone, indicating that UV/PAA could decrease the microbial regrowth potential after PAA disinfection alone.

Tenets of a holistic approach to drinking water-associated pathogen research, management, and communication

In recent years, drinking water-associated pathogens that can cause infections in immunocompromised or otherwise susceptible individuals (henceforth referred to as DWPI), sometimes referred to as opportunistic pathogens or opportunistic premise plumbing pathogens, have received considerable attention. DWPI research has largely been conducted by experts focusing on specific microorganisms or within silos of expertise. The resulting mitigation approaches optimized for a single microorganism may have unintended consequences and trade-offs for other DWPI or other interests (e.g., energy costs and conservation). For example, the ecological and epidemiological issues characteristic of Legionella pneumophila diverge from those relevant for Mycobacterium avium and other nontuberculous mycobacteria. Recent advances in understanding DWPI as part of a complex microbial ecosystem inhabiting drinking water systems continues to reveal additional challenges: namely, how can all microorganisms of concern be managed simultaneously? In order to protect public health, we must take a more holistic approach in all aspects of the field, including basic research, monitoring methods, risk-based mitigation techniques, and policy. A holistic approach will (i) target multiple microorganisms simultaneously, (ii) involve experts across several disciplines, and (iii) communicate results across disciplines and more broadly, proactively addressing source water-to-customer system management.

Mucormycosis: A deadly black fungus infection among COVID-19 patients in India

After first phase of Covid-19, the second wave affects a lot to the Indians with mysterious fungal infection known as Mucormycosis. Here, we reviewed clinical pathogenesis, signs, symptoms and treatment against black fungus. The conclusion revealed that use of immunosuppressant to combat Covid-19 also increases the risk to get infected with mucormycosis. Patients with hyperglycemia, ketoacidosis, solid organ or bone marrow transplantion, liver cirrhosis, neutropenia are more susceptible to get attacked by Mucormycosis moulds. Early diagnosis, removal of predisposing factors, timely antifungal therapy with surgical removal of all infected tissues and adjunctive therapies are four major factors to eradicate Mucormycosis.

Light-emitting diodes effect on Aspergillus species in filtered surface water: DNA damage, proteome response and potential reactivation

DNA damage and changes in proteome response can occur as a consequence of UV light exposure. The emerging light-emitting diodes (LEDs) can be acquired with different wavelengths. In this study, LEDs that emit at 255 nm and 265 nm were selected to test the DNA damage and proteome response after inactivation of A. fumigatus, A. niger and A. terreus spiked into filtered surface water. Additionally, photoreactivation and dark repair studies were performed to evaluate the potential ability of the spores to recover after UV exposure. Results showed that both LEDs were able to induce the formation of cyclobutane pyrimidine dimers in A. fumigatus and A. terreus whereas, for A. niger, the formation of cyclobutane pyrimidine dimers was only detected when the LEDs that induced inactivation (that emit at 265 nm) were used. Proteome response showed that UV radiation treatment triggered different types of stress response, mainly concerning the protection from oxidative stress by A. fumigatus and A. terreus. Photoreactivation was detected for all the species except A. niger and, no dark repair was observed.

Fungi in dialysis water and dialysate: occurrence, susceptibility to antifungal agents and biofilm production capacity

The aim of this study was to investigate the occurrence of fungi in dialysis water and dialysate, in addition to evaluating the susceptibility to antifungals and the biofilm production capacity of isolated microorganisms. The samples were collected in three hemodialysis units in Bauru (Brazil), every 15 days (July 2017-June 2018) at post-reverse osmosis, reuse, and dialysate points. The fungi were isolated by spread plate on Sabouraud dextrose agar. Filamentous fungi were phenotypically identified and yeasts were subjected to molecular evaluation of the ITS region. Susceptibility test to antifungals was carried out by the broth microdilution method and biofilm production capacity was evaluated in microtiter plates using crystal violet staining. Fungi were isolated in 52/216 (24.1%) samples, with an average count of 16.3 (10-40) CFU/mL. Overall, 61 microorganisms were identified, with 54 (88.5%) filamentous fungi and 7 (11.5%) yeasts. The main genera included were Penicillium, Cladosporium, Scedosporium, Rhinocladiella, Fusarium, and Emmonsia. Most isolates showed high values of minimum inhibitory concentration for 5-flucytosine and fluconazole and 35/45 (77.8%) isolates were classified as strong producers of biofilm. In order to increase the safety of the dialysis process, the adoption of control measures and monitoring of fungi in hemodialysis fluids is suggested.

Mycosands: Fungal diversity and abundance in beach sand and recreational waters - Relevance to human health

The goal of most studies published on sand contaminants is to gather and discuss knowledge to avoid faecal contamination of water by run-offs and tide-retractions. Other life forms in the sand, however, are seldom studied but always pointed out as relevant. The Mycosands initiative was created to generate data on fungi in beach sands and waters, of both coastal and freshwater inland bathing sites. A team of medical mycologists and water quality specialists explored the sand culturable mycobiota of 91 bathing sites, and water of 67 of these, spanning from the Atlantic to the Eastern Mediterranean coasts, including the Italian lakes and the Adriatic, Baltic, and Black Seas. Sydney (Australia) was also included in the study. Thirteen countries took part in the initiative. The present study considered several fungal parameters (all fungi, several species of the genus Aspergillus and Candida and the genera themselves, plus other yeasts, allergenic fungi, dematiaceous fungi and dermatophytes). The study considered four variables that the team expected would influence the results of the analytical parameters, such as coast or inland location, urban and non-urban sites, period of the year, geographical proximity and type of sediment. The genera most frequently found were Aspergillus spp., Candida spp., Fusarium spp. and Cryptococcus spp. both in sand and in water. A site-blind median was found to be 89 Colony-Forming Units (CFU) of fungi per gram of sand in coastal and inland freshwaters, with variability between 0 and 6400 CFU/g. For freshwater sites, that number was 201.7 CFU/g (0, 6400 CFU/g (p = 0.01)) and for coastal sites was 76.7 CFU/g (0, 3497.5 CFU/g). For coastal waters and all waters, the median was 0 CFU/ml (0, 1592 CFU/ml) and for freshwaters 6.7 (0, 310.0) CFU/ml (p < 0.001). The results advocate that beaches should be monitored for fungi for safer use and better management.

Mycological Investigation of Bottled Water Dispensers in Healthcare Facilities

The usage of bottled water dispensers (BWDs) has spread worldwide. Despite their popularity, few studies have dealt with their microbial contaminants, and little attention is given to their fungal contamination. To our knowledge this is the first mycological study of BWDs in Europe. 36 devices have been examined in Budapest, Hungary. Despite of the strictly regulated water hygiene system in Hungary, molds and yeasts were detected in 86.8% of the samples, 56.76% were highly contaminated. Elevated heterotrophic plate counts were also observed in all samples compared to that of Hungarian drinking water. As all physical and chemical water quality characteristics have met the relevant national and European parametric values and neither totally explained the results of microbial counts, the effect of usage and maintenance habits of the devices were examined. Fungal concentrations were affected by the time elapsed since disinfection, days remaining until expiration of bottles, month of sampling and exposure to sunlight during storage. Microbes are able to proliferate in the bottled water and disperse inside the BWDs. Many of the detected fungal species (Sarocladium kiliense, Acremonium sclerotigenum/egyptiacum, Exophiala jeanselmei var. lecanii-corni, Exophiala equina, Meyerozyma guilliermondii, Cystobasidium slooffiae, Aspergillus jensenii, Bisifusarium biseptatum) are opportunistic pathogens for subpopulations of sensitive age groups and patients with immunodeficient conditions, including cystic fibrosis. Thus BWDs may pose a health risk to visitors of healthcare institutions, especially to patients with oral lesions in dental surgeries. The study draws attention to the need to investigate microbial contamination of these devices in other countries as well.

Antifungal agents, yeast abundance and diversity in surface water: Potential risks to water users

South African surface waters are subject to various forms of pollution. Recent findings in aquatic systems suggest an association exists between yeast diversity, chemical pollutants and land coverage, which are important water quality determinants. Yeast abundance and diversity, as well as antifungal agents in two river systems in South Africa, were investigated and related to the existing land coverage. Yeast abundance and diversity were determined from environmental DNA by quantitative polymerase chain reaction and next-generation sequencing, respectively, of the 26S ribosomal ribonucleic acid (rRNA) gene. Antifungal agents were qualitatively and/or quantitatively detected by ultra-high-pressure liquid chromatography-mass spectrometry. Analyses of 2 031 714 high-quality 26S rRNA sequences yielded 5554 amplicon sequence variants (ASVs)/species. ASV richness and Shannon-Wiener index of diversity reflected the southward flow of the river with higher values observed downstream compared to the upstream. Fluconazole concentrations were quantifiable in only two samples; 178 and 271 ng L^-1. Taxonomically, at least 20 yeast species were detected, including the dominant Candida tropicalis, Cryptococcus spp. as well as the lesser dominant Bensingtonia bomiensis, Fereydounia khargensis, Hericium erinaceus, Kondoa changbaiensi, Pseudozyma spp. and Sphacelotheca pamparum. The two dominant species are known opportunistic pathogens which had antifungal resistant traits in previous studies from the same rivers and therefore is a public health threat. The present study provides further evidence that yeasts should be included as part of water quality parameters, especially in developing countries where much of the population are economically disadvantaged, and also immunocompromised due to age and disease.

Inactivation of waterborne fungal spores by 1-bromo-3-chloro-5,5-dimethylhydantoin: Kinetics, influencing factors and mechanisms

Fungal contamination in drinking water source has become a problem worth studying, as waterborne fungi may cause deterioration of water quality and outbreak of diseases. Various disinfection methods have been explored to control fungal spores in drinking water, such as chlor(am)ination, ozonation, chlorine dioxide treatment, but these methods are not appropriate for remote areas, owing to the difficulties in preparation, carriage and storage. In this study, a powdery disinfectant of 1-bromo-3-chloro-5,5-dimethylhydantoin (BCDMH), which facilitated transportation and preservation, was firstly chosen to inactivate opportunistic pathogens of Aspergillus niger (A. niger) and Penicillium polonicum (P. polonicum). The results revealed that the inactivation kinetics of fungal spores by BCDMH fitted to Chick-Watson model well, with the inactivation rate constant of 0.011 and 0.034 L mg^-1 min^-1 for A. niger and P. polonicum, respectively. Acidic condition and high temperature promoted the inactivation by BCDMH. Compared with chlorine, BCDMH showed relative weaker ability on inactivation of fungal spores. However, it was demonstrated that the inactivation efficiency of BCDMH was obviously enhanced by adding halide ions, with 11 or 36 folds for A. niger and 4 or 15 folds for P. polonicum by adding 40 μM Br^- or I^-. The inactivation mechanisms were detected by flow cytometry and scanning electron microscope. Fungal spores lost their culturability firstly, then membrane integrity was damaged. Meanwhile, the esterase activity and intracellular reactive oxygen species level changed, and finally intracellular adenosine triphosphate released.

Inactivation of Aspergillus species in real water matrices using medium pressure mercury lamps

The aim of this work is to understand the inactivation efficiency of medium pressure mercury lamps, measured in terms of growth inhibition as well as cell death, damage and response, using three strains from three different Aspergillus species (A. fumigatus, A. niger and, A. terreus) spiked in filtered surface water. A complete characterization of the effect of the treatment on each strain of the fungal species was assessed considering spores' morphology, cell wall integrity and enzymatic activity, the formation of pyrimidine dimers in the DNA and proteome analysis. Results showed that, when subjected to medium pressure mercury lamps, A. niger is the most resistant to inactivation, that both A. fumigatus and A. niger suffer more morphological changes and present a higher number of damaged spores and A. terreus presented more dead spores. DNA damages detected in A. niger were able to be repaired to some extent, under both light and dark conditions. Finally, proteome analysis showed that the UV radiation treatment triggered different types of stress response, including cell wall reorganization and DNA repair in A. fumigatus and A. terreus, and oxidative stress responses like the increase in production of citric acid and itaconic acid in A. niger and A. terreus, respectively.

Deep Learning Model for Pathogen Classification Using Feature Fusion and Data Augmentation

Background:

Bacterial pathogens are deadly for animals and humans. The ease of their dissemination, coupled with their high capacity for ailment and death in infected individuals, makes them a threat to society.

Objective:

Due to high similarity among genera and species of pathogens, it is sometimes difficult for microbiologists to differentiate between them. Their automatic classification using deep-learning models can help in reliable, and accurate outcomes.

Method:

Deep-learning models, namely; AlexNet, GoogleNet, ResNet101, and InceptionV3 are used with numerous variations including training model from scratch, fine-tuning without pre-trained weights, fine-tuning along with freezing weights of initial layers, fine-tuning along with adjusting weights of all layers and augmenting the dataset by random translation and reflection. Moreover, as the dataset is small, fine-tuning and data augmentation strategies are applied to avoid overfitting and produce a generalized model. A merged feature vector is produced using two best-performing models and accuracy is calculated by xgboost algorithm on the feature vector by applying cross-validation.

Results:

Fine-tuned models where augmentation is applied produces the best results. Out of these, two-best-performing deep models i.e. (ResNet101, and InceptionV3) selected for feature fusion, produced a similar validation accuracy of 95.83 with a loss of 0.0213 and 0.1066, and a testing accuracy of 97.92 and 93.75, respectively. The proposed model used xgboost to attained a classification accuracy of 98.17% by using 35-folds cross-validation.

Conclusion:

The automatic classification using these models can help experts in the correct identification of pathogens. Consequently, they can help in controlling epidemics and thereby minimizing the socio-economic impact on the community.

Development of an Immunofluorescence Assay Module for Determination of the Mycotoxin Zearalenone in Water

Project Aquafluosense is designed to develop prototypes for a fluorescence-based instrumentation setup for in situ measurements of several characteristic parameters of water quality. In the scope of the project an enzyme-linked fluorescent immunoassay (ELFIA) method has been developed for the detection of several environmental xenobiotics, including mycotoxin zearalenone (ZON). ZON, produced by several plant pathogenic Fusarium species, has recently been identified as an emerging pollutant in surface water, presenting a hazard to aquatic ecosystems. Due to its physico-chemical properties, detection of ZON at low concentrations in surface water is a challenging task. The 96-well microplate-based fluorescence instrument is capable of detecting ZON in the concentration range of 0.09-400 ng/mL. The sensitivity and accuracy of the analytical method has been demonstrated by a comparative assessment with detection by high-performance liquid chromatography and by total internal reflection ellipsometry. The limit of detection of the method, 0.09 ng/mL, falls in the low range compared to the other reported immunoassays, but the main advantage of this ELFIA method is its efficacy in combined in situ applications for determination of various important water quality parameters detectable by induced fluorimerty-e.g., total organic carbon content, algal density or the level of other organic micropollutants detectable by immunofluorimetry. In addition, the immunofluorescence module can readily be expanded to other target analytes if proper antibodies are available for detection.

Microbial Communities of Meat and Meat Products: An Exploratory Analysis of the Product Quality and Safety at Selected Enterprises in South Africa

Consumption of food that is contaminated by microorganisms, chemicals, and toxins may lead to significant morbidity and mortality, which has negative socioeconomic and public health implications. Monitoring and surveillance of microbial diversity along the food value chain is a key component for hazard identification and evaluation of potential pathogen risks from farm to the consumer. The aim of this study was to determine the microbial diversity in meat and meat products from different enterprises and meat types in South Africa. Samples (n = 2017) were analyzed for Yersinia enterocolitica, Salmonella species, Listeria monocytogenes, Campylobacter jejuni, Campylobacter coli, Staphylococcus aureus, Clostridium perfringens, Bacillus cereus, and Clostridium botulinum using culture-based methods. PCR was used for confirmation of selected pathogens. Of the 2017 samples analyzed, microbial ecology was assessed for selected subsamples where next generation sequencing had been conducted, followed by the application of computational methods to reconstruct individual genomes from the respective sample (metagenomics). With the exception of Clostridium botulinum, selective culture-dependent methods revealed that samples were contaminated with at least one of the tested foodborne pathogens. The data from metagenomics analysis revealed the presence of diverse bacteria, viruses, and fungi. The analyses provide evidence of diverse and highly variable microbial communities in products of animal origin, which is important for food safety, food labeling, biosecurity, and shelf life limiting spoilage by microorganisms.

The microbial ecology of a Mediterranean chlorinated drinking water distribution systems in the city of Valencia (Spain)

Drinking water distribution systems host extensive microbiomes with diverse biofilm communities regardless of treatment, disinfection, or operational practices. In Mediterranean countries higher temperatures can accelerate reactions and microbial growth that may increase aesthetic water quality issues, particularly where material deposits can develop as a result of net zero flows within looped urban networks. This study investigated the use of flow and turbidity monitoring to hydraulically manage mobilisation of pipe wall biofilms and associated material from the Mediterranean city of Valencia (Spain). Pipe sections of different properties were subjected to controlled incremental flushing with monitoring and sample collection for physico-chemical and DNA analysis with Illumina sequencing of bacterial and fungal communities. A core microbial community was detected throughout the network with microorganisms like Pseudomonas, Aspergillus or Alternaria increasing during flushing, indicating greater abundance in underlying and more consolidated material layers. Bacterial and fungal communities were found to be highly correlated, with bacteria more diverse and dynamic during flushing whilst fungi were more dominant and less variable between sampling sites. Results highlight that water quality management can be achieved through hydraulic strategies yet understanding community dynamics, including the fungal component, will be key to maintaining safe and ultimately beneficial microbiomes in drinking water distribution systems.

Water-Transmitted Fungi are Involved in Degradation of Concrete Drinking Water Storage Tanks

Global warming, globalization, industrialization, and the rapidly growing population at present increasingly affect the production of safe drinking water. In combination with sustainable bio-based or recycled materials, used for water distribution systems, these factors promote emerging pathogens, including fungi. They can proliferate in oligotrophic water systems, affect the disinfection process, degrade building materials, and cause diseases in humans. In this study, we explored fungal-based degradation of modern concrete water storage tanks and the presence of fungi in chlorinated drinking water at the entrance and exit of the tanks. The degradation potential of isolated 52 fungal strains and their growth at different oligotrophic conditions was tested in vitro. Forty percent of strains grew at extremely oligotrophic conditions, and 50% classified as aerophilic. Two-thirds of tested strains produced acids, with Penicillium strains as the best producers. Only 29.7% of the strains were able to grow at 37 °C, and none of them was isolated from drinking water at consumers' taps. Although not yet part of the guidelines for building materials in contact with drinking water, fungi should be taken into consideration in case of visible degradation. Their number of consumers' endpoints should be checked to exclude possible health risks for consumers.

Suspect and Target Screening of Natural Toxins in the Ter River Catchment Area in NE Spain and Prioritisation by Their Toxicity

This study presents the application of a suspect screening approach to screen a wide range of natural toxins, including mycotoxins, bacterial toxins, and plant toxins, in surface waters. The method is based on a generic solid-phase extraction procedure, using three sorbent phases in two cartridges that are connected in series, hence covering a wide range of polarities, followed by liquid chromatography coupled to high-resolution mass spectrometry. The acquisition was performed in the full-scan and data-dependent modes while working under positive and negative ionisation conditions. This method was applied in order to assess the natural toxins in the Ter River water reservoirs, which are used to produce drinking water for Barcelona city (Spain). The study was carried out during a period of seven months, covering the expected prior, during, and post-peak blooming periods of the natural toxins. Fifty-three (53) compounds were tentatively identified, and nine of these were confirmed and quantified. Phytotoxins were identified as the most frequent group of natural toxins in the water, particularly the alkaloids group. Finally, the toxins identified to levels 2 and 1 were prioritised according to their bioaccumulation factor, biodegradability, frequency of detection, and toxicity. This screening and prioritisation approach resulted in different natural toxins that should be further assessed for their ecotoxicological effects and considered in future studies.

Inactivation of fungal spores in water using ozone: Kinetics, influencing factors and mechanisms

Fungal contamination of drinking water sources is increasingly threatening the environment and human health. In this study, the inactivation of three genera of dominant fungi in drinking water sources using ozone was first reported. The inactivation of the fungal spores by ozone could be divided into two distinct stages: first a rapid reduction in survival, and then the inactivation at a slower rate. The secondary stage inactivation fitted the Chick-Watson model well, and there was no significant difference in the second-order inactivation rate constants of the three fungal spores (0.199-0.209 L mg^-1 min^-1). The inactivation rate constants of fungal spores by molecular ozone were much lower than those of viruses, which were equivalent to that of Cryptosporidium. The increase in pH and temperature showed a positive effect on the inactivation rate. Damage to cell membranes, leakage of intracellular compounds, and changes of reactive oxygen species and esterase activity in the spores were detected after inactivation. The results indicated that ozone inactivated fungal spores by firstly destroying cell walls and membranes and then causing the release of intracellular compounds. The fungicidal efficiency of ozone was superior to those of chlorine and chlorine dioxide. In addition, the inactivation efficiency of ozone on fungal spores in real water matrices was reduced to 50.7-91.2% of the efficiency in phosphate buffer. In conclusion, ozone showed high efficiency in the inactivation of fungal spores and could be used as an alternative disinfectant for fungal contamination in drinking water sources.

Aflatoxin B1 induces reactive oxygen species-dependent caspase-mediated apoptosis in normal human cells, inhibits Allium cepa root cell division, and triggers inflammatory response in zebrafish larvae

Mycotoxin contamination of food and water is a serious global concern. Aflatoxin B1 (AFB1) is a deadly mycotoxin that contaminates both food and water bodies in the environment. AFB1 is reported to cause severe health issues, including hepatotoxicity, teratogenicity, and immunotoxicity in humans; however, the mechanistic effects on plant and aquatic animals are not fully understood. To obtain a clear understanding of the effects of AFB1 on the ecosystem, we examined the influence of AFB1 exposure on different model systems corresponding to various habitats. In the current study, AFB1 contamination consequences were studied on a human normal cell lines (HaCaT, CCD 841 CoN), meristematic Allium cepa (onion) root cells, and zebrafish embryonic development. Our results clearly indicate that concentrations of AFB1 >10 μM are toxic to HaCaT cells. Morphological changes of HaCaT and CCD 841 CoN cells were clearly observed after exposure to AFB1. Particularly in HaCaT cells, treatment with 50 μM and 100 μM AFB1induces oxidative stress by excessive endogenous free-radical production such as ROS and NO generation. These consequences accelerate the ROS-dependent DNA damage events, which subsequently result in caspase mediated programmed cell death. Exposure of A. cepa root cells to AFB1 for 24 h resulted in abnormal cell division. A. cepa root cells subjected to AFB1 treatment showed a significant concentration-dependent increase in metaphase arrest. Exposure of zebrafish embryos to AFB1 also revealed that AFB1 contamination restricts the larval growth and development, resulting in a remarkably increased zebrafish mortality rate. Collectively, results of the current study indicate that AFB1 contamination triggers the programmed cell death machinery, subsequently affecting the ecosystem.

Occurrence of Fungi in the Potable Water of Hospitals: A Public Health Threat

Since the last decade, attention towards the occurrence of fungi in potable water has increased. Commensal and saprophytic microorganisms widely distributed in nature are also responsible for causing public health problems. Fungi can contaminate hospital environments, surviving and proliferating in moist and unsterile conditions. According to Italian regulations, the absence of fungi is not a mandatory parameter to define potable water, as a threshold value for the fungal occurrence has not been defined. This study evaluated the occurrence of fungi in potable water distribution systems in hospitals. The frequency of samples positive for the presence of fungi was 56.9%; among them, filamentous fungi and yeasts were isolated from 94.2% and 9.2% of the samples, respectively. The intensive care unit (87.1%) had the highest frequency of positive samples. Multivariable model (p < 0.0001), the variables of the period of the year (p < 0.0001) and type of department (p = 0.0002) were found to be statistically significant, suggesting a high distribution of filamentous fungi in the potable water of hospitals. Further studies are necessary to validate these results and identify the threshold values of fungi levels for different types of water used for various purposes to ensure the water is safe for consumption and protect public health.

Microorganisms populating the water-related indoor biome

Modernisation of our households created novel opportunities for microbial growth and thus changed the array of microorganisms we come in contact with. While many studies have investigated microorganisms in the air and dust, tap water, another major input of microbial propagules, has received far less attention. The quality of drinking water in developed world is strictly regulated to prevent immediate danger to human health. However, fungi, algae, protists and bacteria of less immediate concern are usually not screened for. These organisms can thus use water as a vector of transmission into the households, especially if they are resistant to various water treatment procedures. Good tolerance of unfavourable abiotic conditions is also important for survival once microbes enter the household. Limitation of water availability, high or low temperatures, application of antimicrobial chemicals and other measures are taken to prevent indoor microbial overgrowth. These conditions, together with a large number of novel chemicals in our homes, shape the diversity and abundance of indoor microbiota through constant selection of the most resilient species, resulting in a substantial overlap in diversity of indoor and natural extreme environments. At least in fungi, extremotolerance has been linked to human pathogenicity, explaining why many species found in novel indoor habitats (such as dishwasher) are notable opportunistic pathogens. As a result, microorganisms that often enter our households with water and are then enriched in novel indoor habitats might have a hitherto underestimated impact on the well-being of the increasingly indoor-bound human population. KEY POINTS: Domestic environment harbours a large diversity of microorganisms. Microbiota of water-related indoor habitats mainly originates from tap water. Bathrooms, kitchens and household appliances select for polyextremotolerant species. Many household-related microorganisms are human opportunistic pathogens.

Broad Diversity of Fungi in Hospital Water

INTRODUCTION

Some studies have reported the occurrence of microorganisms isolated from water. Considering these microorganisms, fungi are known to occur ubiquitously in the environment, including water, and some are pathogenic and may cause health problems, especially in immunocompromised individuals. The aim of this study was to identify fungi in hospital water samples and to correlate their presence with the concentration of free residual chlorine.

METHODS

Water samples (100 mL) were collected from taps (n = 74) and water purifiers (n = 14) in different locations in a university hospital. Samples were filtered through a nitrocellulose membrane and placed on Sabouraud dextrose agar and incubated for 24 hours at 30°C. Fungi were identified according to established methods based on macroscopic and microscopic characteristics (filamentous) and physiological tests (yeasts). Free chlorine residual content was measured at the time of sample collection.

RESULTS

Seventy species of fungi were identified in the water samples and about 56% of the water samples contained culturable fungi. Cladosporium oxysporum, Penicillium spinulosum, and Aspergillus fumigatus were the most common filamentous fungi. Aureobasidium pullulans and Candida parapsilosis were the most common yeasts. Chemical analyses revealed that free residual chlorine was present in 81.8% of the samples within recommended concentrations. Among samples from water purifiers, 92.9% showed low levels of free residual chlorine (<0.2 mg/L). There was no significant association between chlorine concentrations (either within or outside the recommended range) and the presence of filamentous fungi and yeasts.

CONCLUSIONS

This study showed that hospital water can be a reservoir for fungi, some of which are potentially harmful to immunocompromised patients. Free residual chlorine was ineffective in some samples.

Stress Tolerance of Yeasts Dominating Reverse Osmosis Membranes for Whey Water Treatment

Filamentous yeast species belonging to the closely related Saprochaete clavata and Magnusiomyces spicifer were recently found to dominate biofilm communities on the retentate and permeate surface of Reverse Osmosis (RO) membranes used in a whey water treatment system after CIP (Cleaning-In-Place). Microscopy revealed that the two filamentous yeast species can cover extensive areas due to their large cell size and long hyphae formation. Representative strains from these species were here further characterized and displayed similar physiological and biochemical characteristics. Both strains tested were able to grow in twice RO-filtrated permeate water and metabolize the urea present. Little is known about the survival characteristics of these strains. Here, their tolerance toward heat (60, 70, and 80°C) and Ultraviolet light (UV-C) treatment at 255 nm using UV-LED was assessed as well as their ability to form biofilm and withstand cleaning associated stress. According to the heat tolerance experiments, the D60°C of S. clavata and M. spicifer is 16.37 min and 7.24 min, respectively, while a reduction of 3.5 to >4.5 log (CFU/mL) was ensured within 5 min at 70°C. UV-C light at a dose level 10 mJ/cm2 had little effect, while doses of 40 mJ/cm2 and upward ensured a ≥4log reduction in a static laboratory scale set-up. The biofilm forming potential of one filamentous yeast and one budding yeast, Sporopachydermia lactativora, both isolated from the same biofilm, was compared in assays employing flat-bottomed polystyrene microwells and peg lids, respectively. In these systems, employing both nutrient rich as well as nutrient poor media, only the filamentous yeast was able to create biofilm. However, on RO membrane coupons in static systems, both the budding yeast and a filamentous yeast were capable of forming single strain biofilms and when these coupons were exposed to different simulations of CIP treatments both the filamentous and budding yeast survived these. The dominance of these yeasts in some filter systems tested, their capacity to adhere and their tolerance toward relevant stresses as demonstrated here, suggest that these slow growing yeasts are well suited to initiate microbial biofouling on surfaces in low nutrient environments.

A comparative analysis of drinking water employing metagenomics

The microbiological content of drinking water traditionally is determined by employing culture-dependent methods that are unable to detect all microorganisms, especially those that are not culturable. High-throughput sequencing now makes it possible to determine the microbiome of drinking water. Thus, the natural microbiota of water and water distribution systems can now be determined more accurately and analyzed in significantly greater detail, providing comprehensive understanding of the microbial community of drinking water applicable to public health. In this study, shotgun metagenomic analysis was performed to determine the microbiological content of drinking water and to provide a preliminary assessment of tap, drinking fountain, sparkling natural mineral, and non-mineral bottled water. Predominant bacterial species detected were members of the phyla Actinobacteria and Proteobacteria, notably the genera Alishewanella, Salmonella, and Propionibacterium in non-carbonated non-mineral bottled water, Methyloversatilis and Methylibium in sparkling natural mineral water, and Mycobacterium and Afipia in tap and drinking fountain water. Fecal indicator bacteria, i.e., Escherichia coli or enterococci, were not detected in any samples examined in this study. Bacteriophages and DNA encoding a few virulence-associated factors were detected but determined to be present only at low abundance. Antibiotic resistance markers were detected only at abundance values below our threshold of confidence. DNA of opportunistic plant and animal pathogens was identified in some samples and these included bacteria (Mycobacterium spp.), protozoa (Acanthamoeba mauritaniensis and Acanthamoeba palestinensis), and fungi (Melampsora pinitorqua and Chryosporium queenslandicum). Archaeal DNA (Candidatus Nitrosoarchaeum) was detected only in sparkling natural mineral water. This preliminary study reports the complete microbiome (bacteria, viruses, fungi, and protists) of selected types of drinking water employing whole-genome high-throughput sequencing and bioinformatics. Investigation into activity and function of the organisms detected is in progress.

The occurrence of potentially pathogenic filamentous fungi in recreational surface water as a public health risk

Microfungi occurring in surface water may represent an important health risk. Recreational water reservoirs are a potential reservoir of pathogenic fungi. The aim of the study was to assess the diversity of mycobiota in selected artificial bathing reservoirs with regard to its biosafety for the human population. The studies were conducted during the summer of 2016 in three research seasons (June (I), July and August (II), and September (III)), taking into account the various periods of recreational activities. Filamentous fungi were isolated from water samples collected at five different ponds utilized for recreation. From 162 water samples, 149 fungal taxa of filamentous fungi were identified: 140 were classified to species level and only nine to genus level. Aspergillus fumigatus was the dominant species. The highest species richness (S) was noted in June, with 93 fungal taxa (Menhinick's index from 2.65 to 4.49). Additionally, in season I, the highest diversity of fungal species was revealed (Simpson's diversity index from 0.83 to 0.99). The average number of CFU/1 mL sample ranged between 0.4 and 4.6 depending on the time of sampling and ponds. Of all the isolated species, 128 were clinically relevant (11 from RG-2 and 117 from RG-1), highlighting the need to introduce seasonal mycological monitoring of such reservoirs.

Aquatic yeasts: diversity, characteristics and potential health implications

There has been a rising interest in the levels, diversity and potential impacts of yeasts in aquatic environments. Some of the species isolated from such niches are known pathogens or have pathogenic and antifungal resistance features. This deems it necessary to understand the characteristics and potential health implications of such environmental yeasts species. Studies on these subjects are limited. Most studies on aquatic yeasts have linked them to water pollution. However, the current gold standards to determine microbial pollution of water use bacteria as the main indicator organisms. Including yeasts in water quality standards may provide a different dimension on the quality of water when determining its fit-for-use properties. Pathogenic yeasts cause superficial infections or life-threatening infections, especially in immunocompromised people. Some of the yeast species isolated in recent studies were resistant to commonly used antifungal agents of clinical and veterinary relevance. With the high prevalence rate of HIV in sub-Saharan Africa, particularly in South Africa, antifungal resistance is a public concern as it poses serious medical and economic challenges. Most available studies are concerned with clinical environments only. There is, thus, a need to review the literature that also focuses on aquatic environments.

Small but powerful: Light-emitting diodes for inactivation of Aspergillus species in real water matrices

This study addressed the effectiveness of light emitting diodes to achieve inactivation of three different Aspergillus species (Aspergillus fumigatus, Aspergillus niger and Aspergillus terreus) in a real water matrix. Three single small ultraviolet-C diodes emitting light at two different wavelengths were tested: 255 nm that is similar to the wavelength emitted by low pressure mercury lamps and 265 nm that is closer to the maximum absorbance wavelength of DNA. The ultraviolet-C diodes emitting light at 265 nm were found to be more effective than the 255 nm, achieving 3-log, 1-log and 5-log inactivations of Aspergillus fumigatus, Aspergillus niger and Aspergillus terreus using less than 20 mJ/cm² (13,97 mJ/cm²; 7,28 mJ/cm²; 19,74 mJ/cm²). The diodes have also affected the morphology of the fungal spores and increased the percentage of damaged and dead spores.

Biotic Environments Supporting the Persistence of Clinically Relevant Mucormycetes

Clinically relevant members of the Mucorales group can grow and are found in diverse ecological spaces such as soil, dust, water, decomposing vegetation, on and in food, and in hospital environments but are poorly represented in mycobiome studies of outdoor and indoor air. Occasionally, Mucorales are found in water-damaged buildings. This mini review examines a number of specialised biotic environments, including those revealed by natural disasters and theatres of war, that support the growth and persistence of these fungi. However, we are no further forward in understanding exposure pathways or the chronicity of exposure that results in the spectrum of clinical presentations of mucormycosis.

Adhesion of filamentous fungi isolated from drinking water under different process conditions

Filamentous fungi (ff) are consistently recognized as drinking water (DW) inhabitants, typically harboured in biofilms. Their sessile behaviour is still poorly understood. This study aimed the evaluation of the influence of several abiotic factors (substratum, hydrodynamic conditions and nutrient availability) on biofilm formation by Penicillium brevicompactum and P. expansum isolated from DW. Fungal adhesion was quantified on high density polyethylene (HDPE) and polyvinyl chloride (PVC) surfaces using synthetic tap water (STW) and R2A broth, under stagnant or agitated (25 and 150 rpm) conditions. Fungal spore numbers were assessed after staining with Calcofluor White MR2 and epifluorescence microscopy. The surface charge and physicochemical properties of spores were characterized for a mechanistic understanding on the adhesion process. The adhesion kinetics of spores was represented accurately by the Logistic model, in which adhesion increased with time until a maximum level attained before spore germination (8 h after incubation). In general, P. brevicompactum demonstrated to adhere in a higher extent than P. expansum (12 × 10⁴ spores/cm²vs 1.7 × 10⁴ spores/cm²). Moreover, fungal adhesion was potentiated under stagnation and using R2A broth. HDPE and PVC allowed spore adhesion at similar extents. Adhesion predictions based on the extended Derjaguin, Landau, Verwey and Overbeek (XDLVO) theory corroborated the experimental results, highlighting the role of physicochemical surface properties on the adhesion of spores. These results allowed to refine a model for ff biofilm formation. The overall results help to understand key aspects determining the presence of P. brevicompactum and P. expansum biofilms in DW, where stagnant conditions and the presence of nutrients should be avoided to prevent ff biofilm formation.