Search Results (231)

Since its first appearance as a human pathogen in 1976, Legionella pneumophila has been identified as a causative agent of community-acquired pneumonia (CAP). It survives in rivers, bays, lakes, and water reservoirs, and it is categorized as the fourth most common causative agent of CAP leading to hospitalization. We aimed to investigate patterns in which environmental, seasonal and regional factors may affect the prevalence of Legionnaires’ disease in Crete during the last two decades (2000–2022).The data used originated from the national surveillance database and included any person reported with travel-associated Legionnaires’ disease (TALD) between January 2000 and December 2022. Meteorological data were collected from the National Weather Service. The meteorological variables included (max) temperature (in °C), cloudiness (in octas), wind speed (in knots), and relative humidity (RH) (%). The statistical analysis was based on a case-crossover design with 1:1 matching characteristic. We revealed both seasonal and regional effects on the incidence of Legionnaires’ disease. Cases are significantly more frequent in autumn, in comparison to the other three seasons, while Rethymnon is the prefecture with fewer cases in comparison to Chania or Heraklion. In addition, our research showed that the majority of cases occurred during the years 2017–2018. TALD in Crete is significantly associated with temperature in °C and wind speed in knots. Our research suggests that temporal and spatial factors significantly influence disease cases. These results are in line with studies from foreign countries. The study results aspire to expand our knowledge regarding the epidemiological characteristics of Legionnaires’ disease in relation to local, geographical and meteorological factors on the island of Crete. Full article

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

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

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

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

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

As cases of Legionnaires’ disease increase worldwide, there is uncertainty on whether water management plans should focus on the measurement of Legionella species or specifically on L. pneumophila. This paper makes the case that for public water systems and buildings, the target organism should be L. pneumophila, as it is the overwhelming cause of illness, has simple methods for analysis, and remediation procedures avoid unnecessary costs that produce little public health benefit. A review of 930 outbreaks in the United States from 1973 through 2023 showed that there was no public health justification to require public water systems or public buildings (other than healthcare facilities) to monitor or manage for any other species of Legionella other than L. pneumophila. Full article

Background: Since Legionella pneumophila (Lp) is widely present in natural and artificial water environments, it has a high potential risk of outbreak. Diarrhea caused by Lp pulmonary infection is an important symptom of Legionnaires’ disease (LD); however, the underlying mechanism of the diarrhea has not yet been revealed. This not only has a negative impact on clinical diagnosis and treatment, but may also cause misdiagnosis. Methods: In the present study, a mouse model of enteritis caused by pulmonary infection of Lp was established. By using this mouse model, we explored the underlying mechanisms of the enteritis caused by Lp pulmonary infection. Results: The results indicated that the systemic inflammatory response played a very important role in the enteritis phenotype caused by a strong-virulence strain of Lp. Furthermore, we found that the expression of Bcl-2 was downregulated by IL-6 through the p53 signaling pathway, thereby activating the caspase 3 of intestinal epithelial cells (IECs), causing the apoptosis of IECs, and ultimately leading to the enteritis phenotype. Conclusions: The IL-6–caspase 3 axis plays an important role in enteritis caused by Lp pulmonary infection. Full article

Investigating human pathogens in wastewater is crucial for identifying and predicting potential occupational health risks faced by wastewater treatment plant (WWTP) workers. This study aimed to determine the occurrence and levels of Legionella pneumophila, Mycobacterium spp., Arcobacter butzleri, and Aeromonas hydrophila in untreated municipal wastewater. Grab influent, activated sludge, and secondary settling tank (SST) effluent samples were collected bi-weekly over 6 months from 5 WWTPs in Tshwane, South Africa. Mycobacterium spp., A. butzleri, and A. hydrophila were detected using quantitative PCR (qPCR), while Legionella was detected using both a culture method and qPCR. The four pathogens were identified in most samples at varying levels. Legionella pneumophila had a positivity rate of 92%, ranging from 2 to 5.4 log₁₀ MPN/100 mL. Detection rates of Legionella spp., L. pneumophila, and L. pneumophila serogroup 1 were 97%, 75%, and 69%, respectively, with up to 5.3 log₁₀ gene copies (GC)/mL. Importantly, this study demonstrates molecular typing of L. pneumophila serogroup 1 in wastewater, a topic that has been rarely documented. Mycobacterium spp. were detected in all samples at varying levels (log₁₀ GC/mL) in influent (2.8–7.6), activated sludge (4.8–8.9), and SST effluent (3.8–8.9) samples. Arcobacter butzleri and A. hydrophila were detected in 96% and 82% of the samples, respectively, with GC levels in influent, activated sludge, and SST effluent ranging from 0.8 to 6.6, 1.5 to 6.5, and 0.7 to 6.6 log₁₀ GC/mL for A. butzleri, and similar levels for A. hydrophila. These findings underscore the presence of respiratory and enteric pathogens at various treatment points, suggesting potential occupational exposure for WWTP workers. This emphasises the need for microbiological risk assessments (RAs) or reviewing existing RAs and implementing necessary control measures to protect WWTP workers. Full article

HtpB, the chaperonin of the bacterial pathogen L. pneumophila, is found in extracellular locations, even the cytoplasm of host cells. Although chaperonins have an essential cytoplasmic function in protein folding, HtpB exits the cytoplasm to perform extracellular virulence-related functions that support L. pneumophila’s lifestyle. The mechanism by which HtpB reaches extracellular locations is not currently understood. To address this experimental gap, immunoelectron microscopy, trypsin-accessibility assays, and cell fractionation were used to localize HtpB in various L. pneumophila secretion mutants. Dot/Icm type IV secretion mutants displayed less surface-exposed HtpB and more periplasmic HtpB than parent strains. The analysis of periplasmic extracts and outer membrane vesicles of these mutants, where HtpB co-localized with bona fide periplasmic proteins, confirmed the elevated levels of periplasmic HtpB. Genetic complementation of the mutants recovered parent strain levels of surface-exposed and periplasmic HtpB. The export of GSK-tagged HtpB into the cytoplasm of infected cells was also Dot/Icm-dependent. The translocating role of the Dot/Icm system was not specific for HtpB because GroEL, the chaperonin of Escherichia coli, was found at the cell surface and accumulated in the periplasm of Dot mutants when expressed in L. pneumophila. These findings establish that a functional Dot/Icm system is required for HtpB to reach extracellular locations, but the mechanism by which cytoplasmic HtpB reaches the periplasm remains partially unidentified. Full article

Multiple human and plant pathogens are dispersed and transmitted as bioaerosols (e.g., Mycobacterium tuberculosis, SARS-CoV-2, Legionella pneumophila, Aspergillus fumigatus, Phytophthora spp., and Fusarium graminearum). Rapid, on-site methods to detect airborne pathogens would greatly enhance our ability to monitor exposure and trigger early mitigation measures across different settings. Analysis of air samples for microorganisms in a regulatory context is often based on culture-based methods, which are slow, lack specificity, and are not suitable for detecting viruses. Molecular methods (based on nucleic acids) could overcome these challenges. For example, loop-mediated isothermal amplification (LAMP) is rapid, sensitive, specific, and may detect microbial pathogens from air samples in under 60 min. However, the low biomass in air samples makes recovering sufficient nucleic acids for detection challenging. To overcome this, we present a simple method for concentrating bioaerosols collected through liquid impingement (one of the most common methods for bioaerosol collection). This method paired with LAMP (or other molecular approaches) offers simple, rapid, and sensitive detection of pathogens. We validated this method using three airborne pathogens (Mycobacterium tuberculosis, Legionella pneumophila, and Aspergillus fumigatus), and we were able to detect fewer than five cells in a 15 mL liquid impinger air sample in under 60 min. This simple method offers rapid pathogen detection without the use of specialist equipment, and it can be used across healthcare, education, environmental monitoring, and military settings. Full article

Background: Legionella species are the causative agent of Legionnaires’ disease and, as ubiquitous waterborne bacteria, are prone to antimicrobial resistance gene (ARG) acquisition and dissemination due to the antimicrobial contamination of natural environments. Given the potential health risks associated with ARGs, it is crucial to assess their presence in the Legionella population. Methods: The ARGs lpeAB and tet56 were detected in 348 samples, isolates, and DNA extracts using conventional PCR. In a subset of lpeAB-positive isolates, azithromycin (AZT) MIC values were obtained using the EUCAST protocol and LpeAB activity was evaluated through an efflux pump inhibition assay. Results: The lpeAB gene was found in 19% (66/348) of samples, with higher detection rates in the L. pneumophila and L. pneumophila sg1 subgroups, at 30% and 41%, respectively. A positive association between lpeAB and L. pneumophila sg1 was found. The MIC values of the lpeAB-positive isolates ranged from 0.064 to 2 mg/L. LpeAB inhibition resulted in 2- and 4-fold MIC reductions in 10 of the 13 isolates analyzed. One sample each of L. longbeacheae and L. bozemanae was found to possess the tet56 gene. Conclusions: The lpeAB gene is predominant in L. pneumophila sg1. A few isolates with the lpeAB gene exhibited MIC values below the EUCAST tentative highest MIC values for wild-type isolates. Expanding ARG monitoring in Legionella is essential to assess the public health risk of Legionnaires’ disease. Full article