Search Results (373)

Climate change is significantly affecting water availability, emphasising the need for sustainable strategies such as wastewater reuse. While this represents a promising alternative resource, insufficiently treated wastewater may pose health risks, particularly through aerosol formation during irrigation, which can facilitate Legionella transmission. This study aimed to evaluate the presence of Legionella across various stages in a wastewater treatment plant (WWTP) that reuses effluent for agricultural purposes. Samples from the influent, four treatment phases, and the final effluent were analysed using both culture-based methods and quantitative PCR (qPCR) for Legionella spp. and L. pneumophila. qPCR detected Legionella spp. in all samples and L. pneumophila in 66% of them. In contrast, the culture-based analysis showed much lower detection levels, with only one positive sample at the influent stage—likely due to microbial interference or growth inhibition. Although contamination decreased in the final effluent, Legionella was still detected in water designated for reuse (Legionella spp. in 100% and L. pneumophila in 17% of samples). No treatment stage appeared to promote Legionella proliferation, likely due to WWTP characteristics, in addition to wastewater temperature and COD. These findings underscore the importance of monitoring Legionella in reclaimed water and developing effective control strategies to ensure the safe reuse of treated wastewater in agriculture. Full article

The colonization of Legionella spp. in engineered water systems constitutes a major public health threat. In this study, a six-year environmental surveillance (2020–2025) of Legionella colonization in five different types of facilities in Crete, Greece is presented, including hotels, passenger ships, primary healthcare facilities, public hospitals, and private clinics. A total of 1081 water samples were collected and analyzed, and the overall positivity was calculated using culture-based methods. Only 16.46% of the samples exceeded the regulatory limit (>10³ CFU/L) in the total sample, with 44.59% overall Legionella positivity. Colonization by facility category showed the highest rates in primary healthcare facilities with 85.96%, followed by public hospitals (46.36%), passenger ships with 36.93%, hotels with 38.08%, and finally private clinics (21.42%). The association of environmental risk factors with Legionella positivity revealed a strong effect at hot water temperatures < 50 °C (RR = 2.05) and free chlorine residuals < 0.2 mg/L (RR = 2.22) (p < 0.0001). Serotyping analysis revealed the overall dominance of Serogroups 2–15 of L. pneumophila; nevertheless, Serogroup 1 was particularly prevalent in hospitals, passenger ships, and hotels. Based on these findings, the requirement for continuous environmental monitoring and risk management plans with preventive thermochemical controls tailored to each facility is highlighted. Finally, operational disruptions, such as those experienced during the COVID-19 pandemic, especially in primary care facilities and marine systems, require special attention. Full article

In 2020, Directive (EU) 2020/2184 was published and subsequently transposed into Italian legislation via Legislative Decree 18/23 (Lgs.D. 18/23). The Directive aims to protect public health through a proactive approach based on a site-specific risk analysis along the entire water supply chain (Water Safety Plan, WSP). Between February and November 2024, a survey was conducted in Italy to assess both hospitals’ knowledge of Lgs.D. 18/23 and the application of the WSP in these facilities. A total of 300 hospitals were asked to complete an anonymous questionnaire containing 60 questions about the characteristics of the facility and the management of the water network, including the chemical–physical and microbiological monitoring of Legionella and other microbiological parameters. A total of 102 questionnaires were sent out (response rate: 34%), but only 72 were properly completed and analyzed. The results of the chemical–physical monitoring are not presented in this manuscript. Overall, 52.8% of the hospitals were built before 2000, and most are aware of Directive (EU) 2020/2184, Lgs.D.18/23 (80.6%), in particular, Article 9 on the risk assessment and management of internal water systems and the guidelines for its implementation (77.8%). All hospitals perform annual microbiological water testing, including Legionella analysis, with a detection rate of <50%. National guidelines for the implementation of WSPs are known in 75% of the hospitals, but only 38.9% have started planning to implement them, and 13.9% organize staff training on the subject. The questionnaire responses highlight the need to train hospital staff in water system risk management and WSP planning, which will be mandatory by 2029. Full article

Domestic showers are critical points of human exposure to microbial biofilms, which may harbor opportunistic pathogens such as Legionella spp. and nontuberculous Mycobacterium. However, biofilm development in reverse osmosis (RO)-treated drinking water systems remains poorly understood. We tested whether shower plumbing material (flexible polymer hose versus showerhead with inline polyethersulfone filter) and seasonal water variations influence biofilm community assembly. In a controlled field study, commercial shower systems were deployed in households supplied with RO-treated tap water from the KAUST Seawater Desalination Plant; biofilm samples were collected from hoses and filters over 3–17 months. Flow cytometry and 16S rRNA gene amplicon sequencing characterized microbial abundance, diversity, and taxonomic composition. We found that alpha diversity, measured by observed OTUs, was uniformly low, reflecting ultra-low biomass in RO-treated tap water. Beta diversity analyses revealed clear clustering by material type, with hoses exhibiting greater richness and evenness than filters. Core taxa—Pelomonas, Blastomonas, and Porphyrobacter—dominated both biofilm types, suggesting adaptation to low-nutrient, chlorinated conditions. Overall, our results demonstrate that ultra-low-nutrient RO tap water still supports the formation of material-driven, low-diversity biofilms dominated by oligotrophic taxa, underscoring plumbing-material choice as a critical factor for safeguarding shower water quality. These findings advance our understanding of biofilm ecology in RO-treated systems, informing strategies to mitigate potential health risks in shower water. Full article

Pathogens in water systems pose potential health risks. Several countries provide guidelines and risk management strategies for clean water systems. Regarding legionellae, culture-based methods are still the gold standard, whereas molecular methods such as quantitative real-time PCR (qPCR) are controversially discussed among experts as an alternative. It remains questionable as to whether monitoring by qPCR contributes to sustainable water hygiene and effective health prevention. Drinking water samples from 101 buildings were culture-based analyzed to determine the legionellae concentration, along with qPCR tests. The negative predictive values for Legionella spp. and L. pneumophila qPCR regarding the cultivation method were 100% and 98%, respectively. As Legionella spp. DNA is ubiquitously detected, the positive predictive value was low. L. pneumophila DNA was in 18% of the drinking water samples detected by qPCR, among which only 7% was quantifiable. Neither gold-standard methods of cultivation nor qPCR methods alone are suitable to monitor the risk to health by legionellae in water environments adequately. To overcome methodical difficulties, the benefits of a strategic integration of qPCR alongside cultivation methods should be applied to develop a comprehensive protocol for the stepwise analysis of water samples, which can be implemented in international regulatory frameworks in the future. Full article

We have used a rapid, portable assay (Bacterisk) to determine the bacterial water quality along several inland waters in SW England. Water samples were compared by a conventional membrane filter and culture methods for faecal indicator bacteria (FIB; E. coli and enterococci) and endotoxin measurement by Bacterisk. The Bacterisk data, measured in near-real-time, correlate well with both E. coli and enterococci, but also allow the presence of potential pathogens of a non-faecal origin to be detected. The sensitivity was calculated to be 92.96% with a specificity of 46.3% for E. coli with an expanded uncertainty of 22.07% and an Endotoxin Risk detection limit of 25 units. The presence of Bacterisk detectable non-faecal pathogenic bacteria in the water samples was successfully confirmed by Illumina MiSeq sequencing followed by target species-specific qPCR. Sequencing showed the presence of pathogens including Pseudomonas aeruginosa, Salmonella typhi, Acinetobacter baumannii, Shigella spp., and Legionella spp. as well as antimicrobial resistance genes. Furthermore, the portable Bacterisk assay was able to acquire data on the water quality from different locations and at different time points, providing a comprehensive surveillance tool that challenges the time to results by conventional methods (minutes instead of days), yielding compatible results. Full article

Conditions in dental offices are conducive to Legionella pneumophila infections. This is mainly related to the use of a dental unit in the daily clinical work, which is the basic equipment of the office. Water discharged from the dental unit waterlines (DUWLs) and the working tips of the dental unit generates splatter/spatter and bioaerosol, constituting the main sources of potential infection and posing a health threat to both patients and professional dental staff. This article presents a narrative review on the presence and risk associated with Legionella spp., particularly the species L. pneumophila, in the dental office. This paper summarizes current knowledge and offers readers practical references, especially useful in everyday clinical dental practice. Full article

Polyphenols show promising application prospects as a novel natural disinfectant for drinking water. This study employed a simulated pipe network system to investigate the effects of tea polyphenols at an initial concentration of 5 mg/L on the characteristics of biofilm on pipe walls and microbial community succession patterns under different water ages (12–48 h). The results showed that with increasing water age, the tea polyphenol residual concentration gradually decreased, and the biofilm structure significantly evolved: the surface roughness increased from 5.57 nm to 32.8 nm, and the biofilm thickness increased from 40 nm to 150 nm. Microbial community diversity exhibited a trend of first increasing and then decreasing, with the Shannon index reaching its peak (2.847) at a water age of 36 h and remaining significantly higher than the control group (1.336) at all stages. High-throughput sequencing revealed a transition from a single dominant genus of Methylophilus (54.41%) at a water age of 12 h to a multi-genus coexistence pattern at a water age of 48 h, with Methylophilus (24.33%), unclassified_Saprospiraceae (21.70%), and Hydrogenophaga (16.52%) as the main dominant groups. Functional bacterial groups exhibited temporal changes, with biofilm colonization-related genera (Caulobacter, Sphingobium) reaching their peaks at 36 h, while special metabolic genera (Methylophilus, Hydrogenophaga) dominated at 48 h. Potential pathogens in the tea polyphenol treatment groups were effectively controlled at low levels (<0.21%), except for a temporary increase in Legionella (6.50%) at 36 h. Tea polyphenols’ selective inhibition mechanism helps suppress the excessive proliferation of specific genera and reduces the risk of potential pathogen outbreaks. This has important implications for ensuring the microbiological safety of drinking water. Full article

The COVID-19 pandemic has had a profound impact on healthcare systems worldwide, with severe consequences on the global economy and society. The clinical presentation of SARS-CoV-2 infection varies widely, ranging from asymptomatic cases to severe disease and death. Coinfection with other respiratory pathogens in SARS-CoV-2-positive individuals may exacerbate symptom severity and lead to poorer clinical outcomes. Background/Objectives: This study is the first to investigate the prevalence of viral and bacterial co-infections in SARS-CoV-2-positive individuals in Cyprus. Methods: A total of 1111 SARS-CoV-2-positive nasopharyngeal swab samples collected from non-hospitalized patients were analyzed for the presence of 18 viral and 3 bacterial respiratory pathogens. Results: Of these, 51 samples (4.6%) were found to have at least one additional respiratory pathogen. The most frequently detected viruses were rhinovirus/enterovirus (n = 28; 2.5%) and adenovirus (n = 8; 0.7%), while the bacterial pathogens identified were Legionella pneumophila (n = 1; 0.1%) and Bordetella pertussis (n = 1; 0.1%). The highest proportion of co-infections was observed in the youngest age group (<10 years), where 52.9% of co-infections were identified, followed by the 30–39 age group, which accounted for 15.7% of cases. Among single respiratory virus co-infections, rhinovirus/enterovirus (27.5%) and adenovirus (13.7%) were the most frequently detected in the <10 age group, followed by RSV (3.9%), bocavirus, influenza B, HMPV A + B, and coronavirus NL63 (each at 2%). Conclusions: The current study underscores the importance of simultaneous testing for SARS-CoV-2 and other respiratory pathogens, as this may have significant implications for both individual patient care and healthcare services. Full article

Both synthetic and natural rubber-like elastomers are widely employed in industrial applications (such as tires, seals, protective gloves, and damping absorbers) as well as in the food and animal husbandry industries. These materials should be regularly checked for contamination and the associated infectious risk since they frequently come into contact with food, animals, and people. Additionally, they could act as vehicle of microbes and, as a result, diseases. This pilot study investigates the antibacterial efficacy of novel elastomer formulations against Salmonella enterica subsp. enterica serovar Enteritidis and Legionella pneumophila, with possible applications in drinking water distribution systems (DWDSs). This study aims to evaluate the antimicrobial activity of two rubber and five silicone patented elastomers with antibacterial additives. Two microbiological concentrations (10³ and 10⁴ CFU/mL) were used to compare the efficacy of the elastomers. The results showed a significant decrease in bacterial load in several silicone formulations, with two of them showing the strongest bactericidal efficacy against L. pneumophila (0% and 3% survival rates for VMQ105 and VMQ500L formulations, respectively), despite the wide variations in S. Enteritidis inhibition. One rubber elastomer performed better than the other in terms of reducing bacterial survival for both pathogens (NBRCA) while NBROM showed a 0% survival rate only for L. pneumophila. The findings suggest that certain elastomer compositions might lessen the potential infectious risks in water systems or contaminated matrices. Future research may investigate in situ applications, particularly in hospitals or dental offices where these pathogens pose major health risks. Full article

Legionella pneumophila (L. pneumophila), the bacteria causing Legionnaires’ disease, a severe pneumonia with high morbidity and mortality globally. The underreporting of this disease is marked particularly in low-income African countries, where data on Legionellosis remains extremely limited. Gauteng, South Africa’s most densely populated province, faces challenges such as rapid urbanisation, limited access to sanitary facilities, and ageing infrastructure, which can compromise drinking water quality by increasing the presence of bacteria within the water distribution systems. Although research on Legionella in South Africa has been conducted, no research has compared its prevalence in urban and rural households in the country. This study examines the presence and distribution of L. pneumophila and amoeba-associated strains in water distribution systems in both urban (Hillbrow and Atteridgeville) and rural (Zandspruit and Melusi) areas in Gauteng province in South Africa. In total, 134 water samples were obtained from tap faucets and storage containers, and 260 biofilm samples were obtained from tap faucets, storage containers, and toilet bowls. Water samples were analysed for Escherichia coli (E. coli) using the IDEXX Colilert^® and for L. pneumophila using the IDEXX Legiolert^TM assay. Both water and biofilm samples were analysed for evidence of amoeba-associated Legionella using the amoeba enrichment technique. The Colilert assay detected total coliforms in 13% of the urban samples and 25% of the rural samples. The Legiolert^TM assay detected L. pneumophila in 52% of urban and 78% of rural samples. Amoeba-associated L. pneumophila was confirmed in 35% of urban samples and 25% in rural samples. The conventional PCR confirmed L. pneumophila in 81% of both urban and rural samples, while real-time PCR detected L. pneumophila in 97% of urban and 100% of rural samples. In total, 111 water and 19 biofilm samples tested positive for the presence of L. pneumophila across the four areas. These results revealed that L. pneumophila is prevalent in both urban and rural water systems in Gauteng. Full article

It is anticipated that by 2028 there will be a significant increase in the use of HWHP systems in Great Britain (GB). Such systems are considered a better, energy-efficient alternative to fossil fuel-based burners and furnaces, as they use electricity. There are concerns that these systems are susceptible to microbial contamination because they hold water at lower temperatures. In particular, the concern is regarding Legionella contamination, as it can potentially cause disease in the general public and those who are maintaining and replacing these systems. Therefore, this review was focused on understanding the potential risk posed by their increased use and maintenance requirements. This review was approached systematically but was not a full systematic review. There were 61 papers that were considered potentially relevant to the research questions. Of these, 40 papers were considered relevant to the topic of Legionella in HWHP and underwent full article assessment and data extraction. The remaining papers were considered useful for background information. The scope of this review established that Legionella are a known risk in hot water systems that can be carried over to HWHP systems, yet there is minimal evidence to suggest that the current control measures are being appropriately applied to reduce the risk of exposure. When considering countrywide legislation and guidance, it appears that the risk is considered lower in single- or multi-family homes that do not require a centralised system. This review included the assessment of information regarding the safety of working with HWHP systems with regards to maintenance and replacement. The authors found a lack of information regarding these safety concerns. This review is among the first to systematically evaluate the risks of Legionella contamination in HWHP systems. Full article

Free-living protozoa (FLP) can create biofilms in water supply systems and can harbor bacteria, which potentially can be pathogenic, such as Legionella spp. Each year there are more cases of legionellosis in Latvia, so this problem is actual: in 2019 there were 42 cases, but in 2024—88 cases. In this study, the investigated question of the coexistence of FLP and Legionella spp. and bacterial diversity in the drinking water supply systems of Riga, Salaspils, and Jurmala multiapartment buildings and hotels situated in Riga and Jurmala, identify the main FLP genus, and study factors associated with FLP and Legionella spp. occurrence. With microscopy, microbiological, and molecular biology methods, FLP and, specifically, free-living amoeba (FLA) were detected and identified, and Legionella spp. bacteria were isolated. Three FLP genera were identified, including Acanthamoeba, Vahlkampfia, and Hartmanella (Vermamoeba). In hot water, more FLP and Legionella co-existence occurrences were detected. In 64.7% of FLP-positive samples, Hartmanella (Vermamoeba) spp. was detected. Various potentially pathogenic bacteria, such as Coxiella, Leptospira, and Mycobacterium, were detected in the water sample DNA sequences. The average hot water temperature in Riga was lower than 50 °C, which is not enough to minimize the risk of the Legionella bacteria proliferation. The Shannon’s index values showed that bacterial diversity was higher in cold water samples, and the Pearson test showed that the correlation between building floor and Legionella quantity is positive. In this study, we also discovered that differences in bacterial diversity between water samples from two Daugava River banks’ water sources are not significant, but the biggest exception was a much higher percentage of Chaetonotida (hairybellies) in the left river bank samples. Noticeably, there are more Legionella and FLP-positive samples from the kitchen than from the apartment shower. Each hotel building from this study has its own similar bacterial diversity in its water supply system. Full article

The presence of antibiotics and antibiotic resistance genes (ARGs) in natural habitats has recently sparked increased concern. Vertical-flow constructed wetlands (VFCWs) represent a novel approach to reducing these new contaminants. In the current work, four laboratory-scale VFCW models with various substrates were built to decrease oxytetracycline (OTC) and ARGs. The findings showed that the combination of zeolite and activated carbon exhibited high OTC removal efficiency (up to 97%), with lesser accumulation than in other experimental groups. Furthermore, the combination of zeolite and activated carbon had the lowest absolute and relative abundance of ARGs. This was ascribed to the synergistic benefits of zeolite and activated carbon in CW-D, which exceeded other VFCWs in terms of ARGs removal efficiency. The treatment groups had a considerable but not absolute inhibitory impact on ARGs proliferation; this was attributable to the fact that many dominant bacteria in the community under antibiotic stress were antibiotic-resistant, allowing ARGs to propagate more easily. Network analysis and correlation analysis emphasized the importance of horizontal gene transfer (HGT) in ARGs dissemination, and antibiotic pressure is unlikely to have a substantial influence on ARGs propagation in the medium-term future. Furthermore, it was found that hydrophilic phages and Legionella species might serve as possible hosts for ARGs. Full article

Legionella bacterium has the aquatic environment as its natural reservoir. In humans, it can cause a form of interstitial pneumonia called legionellosis which can be transmitted by inhalation of contaminated water aerosols. Legionella infection occurs more frequently in certain more susceptible population groups, including smokers, alcoholics, men, the elderly, as well as people with acquired immunodeficiency syndrome, hematological cancers, and diabetes mellitus. This study aimed to evaluate the effectiveness of the new Italian National Guidelines for the prevention of Legionella colonization in water systems application by analyzing the environmental monitoring data of Legionella carried out in healthcare facilities in the Campania region from 2019 to 2022. The secondary objectives were to estimate the most observed serogroups of L. pneumophila and to analyze the possible link between water temperature and the presence of Legionella, respectively. From our data, it emerged that in 2019, 41.1% of the examined facilities were contaminated by the Legionella genus; in 2020, the contamination percentage was 42.9%; in 2021, it was 54.5%; in 2022, it was 45.5%. Instead, the Legionella positivity rate decreased from 2019 (54.3%) to 2022 (52.4%), suggesting a possible positive influence of more restrictive prevention and control measures. The prevalent species was Legionella pneumophila, particularly serogroup 1; water temperature was the risk factor implicated in Legionella contamination. Full article