Multiplication of Legionella spp. in tap water containing Hartmannella vermiformis

Cervicofacial Subcutaneous Emphysema and Pneumomediastinum Following Class V Resin Restoration: A Case Report

Air can become trapped within the subcutaneous layer of the cervicofacial area, a condition known as subcutaneous emphysema (SE), unexpectedly after routine dental procedures. SE can worsen by extending superiorly to the peri-orbital region and inferiorly to the thorax and abdomen along the fascial planes. Upward progression can result in cavernous sinus thrombosis. Conversely, downward progression can cause a variety of complications such as pneumothorax, mediastinitis, and compression of the venous trunks. The presence of these conditions highlights the significance of prompt identification, precise diagnosis to ascertain the need for immediate intervention, and suitable management to prevent additional unfavorable consequences.

Noninvasive diagnostic biomarkers, genomic profiling, and advanced microscopic imaging in the early detection and characterization of Naegleria fowleri infections leading to primary amebic meningoencephalitis (PAM)

This review delves into the strategies for early detection and characterization of Naegleria fowleri infections leading to primary amoebic meningoencephalitis (PAM). The study provides an in-depth analysis of current diagnostic approaches, including cerebrospinal fluid analysis, brain tissue examination, immunostaining techniques, and culture methods, elucidating their strengths and limitations. It explores the geographical distribution of N. fowleri, with a focus on regions near the equator, and environmental factors contributing to its prevalence. The review emphasizes the crucial role of early detection in PAM management, discussing the benefits of timely identification in treatment, personalized care, and prevention strategies. Genomic profiling techniques, such as conventional PCR, nested PCR, multiplex PCR, and real-time PCR, are thoroughly examined as essential tools for accurate and prompt diagnosis. Additionally, the study explores advanced microscopic imaging techniques to characterize N. fowleri's morphology and behavior at different infection stages, enhancing our understanding of its life cycle and pathogenic mechanisms. In conclusion, this review underscores the potential of these strategies to improve our ability to detect, understand, and combat N. fowleri infections, ultimately leading to better patient outcomes and enhanced public health protection.

Concept about the Virulence Factor of Legionella

Pathogenic species of Legionella can infect human alveolar macrophages through Legionella-containing aerosols to cause a disease called Legionellosis, which has two forms: a flu-like Pontiac fever and severe pneumonia named Legionnaires' disease (LD). Legionella is an opportunistic pathogen that frequently presents in aquatic environments as a biofilm or protozoa parasite. Long-term interaction and extensive co-evolution with various genera of amoebae render Legionellae pathogenic to infect humans and also generate virulence differentiation and heterogeneity. Conventionally, the proteins involved in initiating replication processes and human macrophage infections have been regarded as virulence factors and linked to pathogenicity. However, because some of the virulence factors are associated with the infection of protozoa and macrophages, it would be more accurate to classify them as survival factors rather than virulence factors. Given that the molecular basis of virulence variations among non-pathogenic, pathogenic, and highly pathogenic Legionella has not yet been elaborated from the perspective of virulence factors, a comprehensive explanation of how Legionella infects its natural hosts, protozoans, and accidental hosts, humans is essential to show a novel concept regarding the virulence factor of Legionella. In this review, we overviewed the pathogenic development of Legionella from protozoa, the function of conventional virulence factors in the infections of protozoa and macrophages, the host's innate immune system, and factors involved in regulating the host immune response, before discussing a probably new definition for the virulence factors of Legionella.

The Influence of Organic Matter Origin on the Chlorine Bulk Decay Coefficient in Reclaimed Water

Using reclaimed water has been increasing to manage water shortages arising due to climate change. Research has been conducted on reclaimed water production, but few studies have investigated the pipe network and supply of reclaimed water. Reclaimed water contains greater amounts of organic matter, nutrients, and ionic substances compared to tap water. Therefore, it is highly likely to cause problems, such as water pollution due to microbial propagation in pipes, and leakage due to pipe corrosion, which interfere with water supply system operations. This study investigated the residual chlorine decay characteristics of chlorine disinfectants applied to a control biofilm in reclaimed water pipe networks. The bulk decay coefficient was compared between reclaimed water and a humic acid solution, and the origin of organic matter was analyzed using fluorescence excitation-emission matrices. The experimental results show that residual chlorine was consumed because protein and amino acid-based organic matter reacted more rapidly with chlorine than natural organic matter, such as humic acid. Moreover, chlorine bulk decay occurred rapidly in reclaimed water when total organic carbon was 3 mg/L or higher. These results confirm that removing organic matter during reclaimed water treatment may affect the management of the pipe network system.

Opportunistic pathogens exhibit distinct growth dynamics in rainwater and tap water storage systems

Opportunistic pathogens (OPs) are emerging microbial contaminants in engineered water systems, yet their growth potential in rainwater systems has not been evaluated. The purpose of this study was to compare the growth dynamics of bacterial OPs and related genera (Pseudomonas aeruginosa, Legionella spp., L. pneumophila, Mycobacterium spp., and M. avium), two amoebal hosts (Acanthamoeba spp. and Vermamoeba vermiformis), and the fecal indicator Escherichia coli in simulated rainwater and tap water storage systems (SWSSs). Quantitative polymerase chain reaction (q-PCR) analysis of target microorganisms in SWSS influents and effluents demonstrated that P. aeruginosa and Legionella thrived in rainwater, but not in tap water. V. vermiformis proliferated in both rainwater and tap water polyvinyl chloride (PVC) SWSSs, while mycobacteria were largely absent in rainwater SWSSs. Tank materials exerted stronger influence on target microorganisms in rainwater SWSSs relative to tap water SWSSs, with species-specific responses noted in bulk water and biofilm. For instance, P. aeruginosa and V. vermiformis had the highest gene copy numbers in PVC rainwater SWSS effluents and biofilm, while Legionella peaked in stainless steel rainwater SWSS effluents and PVC rainwater SWSS biofilm. These results highlighted the OP contamination risks in rainwater storage systems and provided insights into rainwater system design and operation in terms of OP control.

The Tail-Specific Protease Is Important for Legionella pneumophila To Survive Thermal Stress in Water and inside Amoebae

Legionella pneumophila (Lp) is an inhabitant of natural and human-made water systems, where it replicates within amoebae and ciliates and survives within biofilms. When Lp-contaminated aerosols are breathed in, Lp can enter the lungs and may infect human alveolar macrophages, causing severe pneumonia known as Legionnaires' disease. Lp is often found in hot water distribution systems (HWDS), which are linked to nosocomial outbreaks. Heat treatment is used to disinfect HWDS and reduce the concentration of Lp However, Lp is often able to recolonize these water systems, indicating an efficient heat shock response. Tail-specific proteases (Tsp) are typically periplasmic proteases implicated in degrading aberrant proteins in the periplasm and important for surviving thermal stress. In Lp Philadelphia-1, Tsp is encoded by the lpg0499 gene. In this paper, we show that Tsp is important for surviving thermal stress in water and for optimal infection of amoeba when a shift in temperature occurs during intracellular growth. We also demonstrate that Tsp is expressed in the postexponential phase but repressed in the exponential phase and that the cis-encoded small regulatory RNA Lpr17 shows the opposite expression, suggesting that it represses translation of tsp In addition, our results show that tsp is regulated by CpxR, a major regulator in Lp, in an Lpr17-independent manner. Deletion of CpxR also reduced the ability of Lp to survive heat shock. In conclusion, our study shows that Tsp is likely an important factor for the survival and growth of Lp in water systems.IMPORTANCE Lp is a major cause of nosocomial and community-acquired pneumonia. Lp is found in water systems, including hot water distribution systems. Heat treatment is a method of disinfection often used to limit the presence of Lp in such systems; however, the benefit is usually short term, as Lp is able to quickly recolonize these systems. Presumably, Lp responds efficiently to thermal stress, but so far, not much is known about the genes involved. In this paper, we show that the Tsp and the two-component system CpxRA are required for resistance to thermal stress when Lp is free in water and when it is inside host cells. Our study identifies critical systems for the survival of Lp in its natural environment under thermal stress.

The small regulatory RNA Lpr10 regulates the expression of RpoS in Legionella pneumophila

Legionella pneumophila (Lp) is a waterborne bacterium able to infect human alveolar macrophages, causing Legionnaires' disease. Lp can survive for several months in water, while searching for host cells to grow in, such as ciliates and amoeba. In Lp, the sigma factor RpoS is essential for survival in water. A previous transcriptomic study showed that RpoS positively regulates the small regulatory RNA Lpr10. In the present study, deletion of lpr10 results in an increased survival of Lp in water. Microarray analysis and RT-qPCR revealed that Lpr10 negatively regulates the expression of RpoS in the postexponential phase. Electrophoretic mobility shift assay and in-line probing showed that Lpr10 binds to a region upstream of the previously identified transcription start sites (TSS) of rpoS. A third putative transcription start site was identified by primer extension analysis, upstream of the Lpr10 binding site. In addition, nlpD TSS produces a polycistronic mRNA including the downstream gene rpoS, indicating a fourth TSS for rpoS. Our results suggest that the transcripts from the third and fourth TSS are negatively regulated by the Lpr10 sRNA. Therefore, we propose that Lpr10 is involved in a negative regulatory feedback loop to maintain expression of RpoS to an optimal level.

Impact of inter-amoebic phagocytosis on the L. pneumophila growth

Free-living amoebae are known to act as replication niches for the pathogenic bacterium Legionella pneumophila in freshwater environments. However, we previously reported that some strains of the Willaertia magna species are more resistant to L. pneumophila infection and differ in their ability to support its growth. From this observation, we hypothesize that L. pneumophila growth in environment could be partly dependent on the composition of amoebic populations and on the possible interactions between different amoebic species. We tested this hypothesis by studying the growth of L. pneumophila and of a permissive free-living amoeba, Vermamoeba vermiformis (formerly named Hartmannella vermiformis), in co-culture with or without other free-living amoebae (Acanthamoeba castellanii and W. magna). We demonstrate the occurrence of inter-amoebic phagocytosis with A. castellanii and W. magna being able to ingest V. vermiformis infected or not infected with L. pneumophila. We also found that L. pneumophila growth is strongly impacted by the permissiveness of each interactive amoeba demonstrating that L. pneumophila proliferation and spread are controlled, at least in part, by inter-amoebic interactions.

Structure, Dynamics and Cellular Insight Into Novel Substrates of the Legionella pneumophila Type II Secretion System

Legionella pneumophila is a Gram-negative bacterium that is able to replicate within a broad range of aquatic protozoan hosts. L. pneumophila is also an opportunistic human pathogen that can infect macrophages and epithelia in the lung and lead to Legionnaires’ disease. The type II secretion system is a key virulence factor of L. pneumophila and is used to promote bacterial growth at low temperatures, regulate biofilm formation, modulate host responses to infection, facilitate bacterial penetration of mucin gels and is necessary for intracellular growth during the initial stages of infection. The L. pneumophila type II secretion system exports at least 25 substrates out of the bacterium and several of these, including NttA to NttG, contain unique amino acid sequences that are generally not observed outside of the Legionella genus. NttA, NttC, and NttD are required for infection of several amoebal species but it is unclear what influence other novel substrates have within their host. In this study, we show that NttE is required for optimal infection of Acanthamoeba castellanii and Vermamoeba vermiformis amoeba and is essential for the typical colony morphology of L. pneumophila. In addition, we report the atomic structures of NttA, NttC, and NttE and through a combined biophysical and biochemical hypothesis driven approach we propose novel functions for these substrates during infection. This work lays the foundation for future studies into the mechanistic understanding of novel type II substrate functions and how these relate to L. pneumophila ecology and disease.

The Golgi Glycoprotein MGAT4D is an Intrinsic Protector of Testicular Germ Cells From Mild Heat Stress

Male germ cells are sensitive to heat stress and testes must be maintained outside the body for optimal fertility. However, no germ cell intrinsic mechanism that protects from heat has been reported. Here, we identify the germ cell specific Golgi glycoprotein MGAT4D as a protector of male germ cells from heat stress. Mgat4d is highly expressed in spermatocytes and spermatids. Unexpectedly, when the Mgat4d gene was inactivated globally or conditionally in spermatogonia, or mis-expressed in spermatogonia, spermatocytes or spermatids, neither spermatogenesis nor fertility were affected. On the other hand, when males were subjected to mild heat stress of the testis (43 °C for 25 min), germ cells with inactivated Mgat4d were markedly more sensitive to the effects of heat stress, and transgenic mice expressing Mgat4d were partially protected from heat stress. Germ cells lacking Mgat4d generally mounted a similar heat shock response to control germ cells, but could not maintain that response. Several pathways activated by heat stress in wild type were induced to a lesser extent in Mgat4d[-/-] heat-stressed germ cells (NFκB response, TNF and TGFβ signaling, Hif1α and Myc genes). Thus, the Golgi glycoprotein MGAT4D is a novel, intrinsic protector of male germ cells from heat stress.

Assessing the impact, genomics and evolution of type II secretion across a large, medically important genus: the Legionella type II secretion paradigm

The type II secretion system (T2SS) plays a major role in promoting bacterial survival in the environment and in human hosts. One of the best characterized T2SS is that of Legionella pneumophila, the agent of Legionnaires’ disease. Secreting at least 25 proteins, including degradative enzymes, eukaryotic-like proteins and novel effectors, this T2SS contributes to the ability of L. pneumophila to grow at low temperatures, infect amoebal and macrophage hosts, damage lung tissue, evade the immune system, and undergo sliding motility. The genes encoding the T2SS are conserved across the genus Legionella, which includes 62 species and >30 pathogens in addition to L. pneumophila. The vast majority of effectors associated with L. pneumophila are shared by a large number of Legionella species, hinting at a critical role for them in the ecology of Legionella as a whole. However, no other species has the same repertoire as L. pneumophila, with, as a general rule, phylogenetically more closely related species sharing similar sets of effectors. T2SS effectors that are involved in infection of a eukaryotic host(s) are more prevalent throughout Legionella, indicating that they are under stronger selective pressure. The Legionella T2SS apparatus is closest to that of Aquicella (another parasite of amoebae), and a significant number of L. pneumophila effectors have their closest homologues in Aquicella. Thus, the T2SS of L. pneumophila probably originated within the order Legionellales, with some of its effectors having arisen within that Aquicella-like progenitor, while other effectors derived from the amoebal host, mimiviruses, fungi and less closely related bacteria.

Vermamoeba vermiformis: a Free-Living Amoeba of Interest

Free-living amoebae are protists that are widely distributed in the environment including water, soil, and air. Although the amoebae of the genus Acanthamoeba are still the most studied, other species, such as Vermamoeba vermiformis (formerly Hartmannella vermiformis), are the subject of increased interest. Found in natural or man-made aquatic environments, V. vermiformis can support the multiplication of other microorganisms and is able to harbor and potentially protect pathogenic bacteria or viruses. This feature is to be noted because of the presence of this thermotolerant amoeba in hospital water networks. As a consequence, this protist could be implicated in health concerns and be indirectly responsible for healthcare-related infections. This review highlights, among others, the consequences of V. vermiformis relationships with other microorganisms and shows that this free-living amoeba species is therefore of interest for public health.

Resistance of Legionella and Acanthamoeba mauritaniensis to heat treatment as determined by relative and quantitative polymerase chain reactions

Legionella and Acanthamoeba spp. persist in harvested rainwater pasteurized at high temperatures (> 72°C) and the interaction mechanisms exhibited between these organisms need to be elucidated. The resistance of two Legionella reference strains (Legionella pneumophila ATCC 33152 and Legionella longbeachae ATCC 33462), three environmental strains [Legionella longbeachae (env.), Legionella norrlandica (env.) and Legionella rowbothamii (env.)] and Acanthamoeba mauritaniensis ATCC 50676 to heat treatment (50-90°C) was determined by monitoring culturability and viability [ethidium monoazide quantitative polymerase chain reaction (EMA-qPCR)]. The expression of metabolic and virulence genes of L. pneumophila ATCC 33152 (lolA, sidF, csrA) and L. longbeachae (env.) (lolA) in co-culture with A. mauritaniensis ATCC 50676 during heat treatment (50-90°C) was monitored using relative qPCR. While the culturability (CFU/mL) and viability (gene copies/mL) of the Legionella strains reduced significantly (p < 0.05) following heat treatment (60-90°C), L. longbeachae (env.) and L. pneumophila ATCC 33152 were culturable following heat treatment at 50-60°C. Metabolically active trophozoites and dormant cysts of A. mauritaniensis ATCC 50676 were detected at 50°C and 60-90°C, respectively. For L. pneumophila ATCC 33152, lolA expression remained constant, sidF expression increased and the expression of csrA decreased during co-culture with A. mauritaniensis ATCC 50676. For L. longbeachae (env.), while lolA was up-regulated at 50-70°C, expression was not detected at 80-90°C and in co-culture. In conclusion, while heat treatment may reduce the number of viable Legionella spp. in monoculture, results indicate that the presence of A. mauritaniensis increases the virulence of L. pneumophila during heat treatment. The virulence of Legionella spp. in co-culture with Acanthamoeba spp. should thus be monitored in water distribution systems where temperature (heat) is utilized for treatment.

Enhanced survival but not amplification of Francisella spp. in the presence of free-living amoebae

Transmission of Francisella tularensis, the etiologic agent of tularemia, has been associated with various water sources. Survival of many waterborne pathogens within free-living amoeba (FLA) is well documented; however, the role of amoebae in the environmental persistence of F. tularensis is unclear. In this study, axenic FLA cultures of Acanthamoeba castellanii, Acanthamoeba polyphaga, and Vermamoeba vermiformis were each inoculated with virulent strains of F. tularensis (Types A and B), the attenuated live vaccine strain, and Francisella novicida. Experimental parameters included low and high multiplicity of infection and incubation temperatures of 25 and 30 °C for 0-10 days. Francisella spp. survival was enhanced by the presence of FLA; however, bacterial growth and protozoa infectivity were not observed. In contrast, co-infections of A. polyphaga and Legionella pneumophila, used as an amoeba pathogen control, resulted in bacterial proliferation, cytopathic effects, and amoebal lysis. Collectively, even though short-term incubation with FLA was beneficial, the long-term effects on Francisella survival are unknown, especially given the expenditure of available amoebal derived nutrients and the fastidious nature of Francisella spp. These factors have clear implications for the role of FLA in Francisella environmental persistence.

Developing an ecologically relevant heterogeneous biofilm model for dental-unit waterlines

This study monitored the biodiversity of microbes cultured from a heterogeneous biofilm which had formed on the lumen of a section of dental waterline tubing over a period of 910 days. By day 2 bacterial counts on the outlet-water showed that contamination of the system had occurred. After 14 days, a biofilm comparable to that of clinical waterlines, consisting of bacteria, fungi and amoebae had formed. This showed that the proprietary silver coating applied to the luminal surface of the commercial waterline tubing failed to prevent biofilm formation. Molecular barcoding of isolated culturable microorganisms showed some degree of the diversity of taxa in the biofilm, including the opportunistic pathogen Legionella pneumophila. Whilst the system used for isolation and identification of contaminating microorganisms may underestimate the diversity of organisms in the biofilm, their similarity to those found in the clinical environment makes this a promising test-bed for future biocide testing.

Convective Mixing in Distal Pipes Exacerbates Legionella pneumophila Growth in Hot Water Plumbing

Legionella pneumophila is known to proliferate in hot water plumbing systems, but little is known about the specific physicochemical factors that contribute to its regrowth. Here, L. pneumophila trends were examined in controlled, replicated pilot-scale hot water systems with continuous recirculation lines subject to two water heater settings (40 °C and 58 °C) and three distal tap water use frequencies (high, medium, and low) with two pipe configurations (oriented upward to promote convective mixing with the recirculating line and downward to prevent it). Water heater temperature setting determined where L. pneumophila regrowth occurred in each system, with an increase of up to 4.4 log gene copies/mL in the 40 °C system tank and recirculating line relative to influent water compared to only 2.5 log gene copies/mL regrowth in the 58 °C system. Distal pipes without convective mixing cooled to room temperature (23-24 °C) during periods of no water use, but pipes with convective mixing equilibrated to 30.5 °C in the 40 °C system and 38.8 °C in the 58 °C system. Corresponding with known temperature effects on L. pneumophila growth and enhanced delivery of nutrients, distal pipes with convective mixing had on average 0.2 log more gene copies/mL in the 40 °C system and 0.8 log more gene copies/mL in the 58 °C system. Importantly, this work demonstrated the potential for thermal control strategies to be undermined by distal taps in general, and convective mixing in particular.

Distribution System Water Quality Affects Responses of Opportunistic Pathogen Gene Markers in Household Water Heaters

Illustrative distribution system operation and management practices shaped the occurrence and persistence of Legionella spp., nontuberculous mycobacteria (NTM), Pseudomonas aeruginosa, and two amoebae host (Acanthamoeba spp., Vermamoeba vermiformis) gene markers in the effluent of standardized simulated household water heaters (SWHs). The interplay between disinfectant type (chlorine or chloramine), water age (2.3-5.7 days) and materials (polyvinyl chloride (PVC), cement or iron) in upstream simulated distribution systems (SDSs) profoundly influenced levels of pathogen gene markers in corresponding SWH bulk waters. For example, Legionella spp. were 3-4 log higher in SWHs receiving water from chloraminated vs chlorinated SDSs, because of disinfectant decay from nitrification. By contrast, SWHs fed with chlorinated PVC SDS water not only harbored the lowest levels of all pathogen markers, but effluent from the chlorinated SWHs were even lower than influent levels in several instances (e.g., 2 log less Legionella spp. and NTM for PVC and 3-5 log less P. aeruginosa for cement). However, pathogen gene marker influent levels correlated positively to effluent levels in the SWHs (P < 0.05). Likewise, microbial community structures were similar between SWHs and the corresponding SDS feed waters. This study highlights the importance and challenges of distribution system management/operation to help control opportunistic pathogens.

Impact of environmental factors on legionella populations in drinking water

To examine the impact of environmental factors on Legionella in drinking water distribution systems, the growth and survival of Legionella under various conditions was studied. When incubated in tap water at 4 °C, 25 °C, and 32 °C, L. pneumophila survival trends varied amongst the temperatures, with the stable populations maintained for months at 25 °C and 32 °C demonstrating that survival is possible at these temperatures for extended periods in oligotrophic conditions. After inoculating coupons of PVC, copper, brass, and cast iron, L. pneumophila colonized biofilms formed on each within days to a similar extent, with the exception of cast iron, which contained 1-log less Legionella after 90 days. L. pneumophila spiked in a model drinking water distribution system colonized the system within days. Chlorination of the system had a greater effect on biofilm-associated Legionella concentrations, with populations returning to pre-chlorination levels within six weeks. Biofilms sampled from drinking water meters collected from two areas within central Arizona were analyzed via PCR for the presence of Legionella. Occurrence in only one area indicates that environmental differences in water distribution systems may have an impact on the survival of Legionella. These results document the impact of different environmental conditions on the survival of Legionella in water.

Rapid and multiplex detection of Legionella's RNA using digital microfluidics

Despite recent advances in the miniaturization and automation of biosensors, technologies for on-site monitoring of environmental water are still at an early stage of development. Prevention of outbreaks caused by pathogens such as Legionella pneumophila would be facilitated by the development of sensitive and specific bioanalytical assays that can be easily integrated in miniaturized fluidic handling systems. In this work, we report on the integration of an amplification-free assay in digital microfluidics (DMF) for the detection of Legionella bacteria based on targeting 16s rRNA. We first review the design of the developed DMF devices, which provide the capability to store up to one hundred nL-size droplets simultaneously, and discuss the challenges involved with on-chip integration of the RNA-based assay. By optimizing the various steps of the assay, including magnetic capture, hybridization duration, washing steps, and assay temperature, a limit of detection as low as 1.8 attomoles of synthetic 16s rRNA was obtained, which compares advantageously to other amplification-free detection systems. Finally, we demonstrate the specificity of the developed assay by performing multiplex detection of 16s rRNAs from a pathogenic and a non-pathogenic species of Legionella. We believe the developed DMF devices combined with the proposed detection system offers new prospects for the deployment of rapid and cost-effective technologies for on-site monitoring of pathogenic bacteria.

Stenotrophomonas maltophilia and Vermamoeba vermiformis relationships: bacterial multiplication and protection in amoebal-derived structures

Stenotrophomonas maltophilia, a bacteria involved in healthcare-associated infections, can be found in hospital water systems. Other microorganisms, such as Free Living amoebae (FLA), are also at times recovered in the same environment. Amongst these protozoa, many authors have reported the presence of Vermamoeba vermiformis. We show here that this amoeba enhances S. maltophilia growth and harbors the bacteria in amoebal-derived structures after 28 days in harsh conditions. These results highlight the fact that particular attention should be paid to the presence of FLA in hospital water systems, because of their potential implication in survival and growth of pathogenic bacterial species.

First evidence of amoebae-mycobacteria association in drinking water network

Free-living amoebae are protozoa ubiquitously found in water systems. They mainly feed on bacteria by phagocytosis, but some bacterial species are able to resist or even escape this lethal process. Among these amoeba resistant bacteria are numerous members of the genus Mycobacterium. Nontuberculous Mycobacteria (NTM) are opportunistic pathogens that share the same ecological niches as amoebae. While several studies have demonstrated the ability of these bacteria to colonise and persist within drinking water networks, there is also strong suspicion that mycobacteria could use amoebae as a vehicle for protection and even replication. We investigated here the presence of NTM and FLA on a drinking water network during an all year round sampling campaign. We observed that 87.6% of recovered amoebal cultures carried high numbers of NTM. Identification of these amoeba and mycobacteria strains indicated that the main genera found in drinking water networks, that is, Acanthamoeba, Vermamoeba, Echinamoeba, and Protacanthamoeba are able to carry and likely to allow replication of several environmental and potentially pathogenic mycobacteria including M. llatzerense and M. chelonae. Direct Sanger sequencing as well as pyrosequencing of environmental isolates demonstrated the frequent association of mycobacteria and FLA, as they are part of the most represented genera composing amoebae's microbiome. This is the first time that an association between FLA and NTM is observed in water networks, highlighting the importance of FLA in the ecology of NTM.

The novel Legionella pneumophila type II secretion substrate NttC contributes to infection of amoebae Hartmannella vermiformis and Willaertia magna

The type II protein secretion (T2S) system of Legionella pneumophila secretes over 25 proteins, including novel proteins that have no similarity to proteins of known function. T2S is also critical for the ability of L. pneumophila to grow within its natural amoebal hosts, including Acanthamoeba castellanii, Hartmannella vermiformis and Naegleria lovaniensis. Thus, T2S has an important role in the natural history of legionnaires' disease. Our previous work demonstrated that the novel T2S substrate NttA promotes intracellular infection of A. castellanii, whereas the secreted RNase SrnA, acyltransferase PlaC, and metalloprotease ProA all promote infection of H. vermiformis and N. lovaniensis. In this study, we determined that another novel T2S substrate that is specific to Legionella, designated NttC, is unique in being required for intracellular infection of H. vermiformis but not for infection of N. lovaniensis or A. castellanii. Expanding our repertoire of amoebal hosts, we determined that Willaertia magna is susceptible to infection by L. pneumophila strains 130b, Philadelphia-1 and Paris. Furthermore, T2S and, more specifically, NttA, NttC and PlaC were required for infection of W. magna. Taken together, these data demonstrate that the T2S system of L. pneumophila is critical for infection of at least four types of aquatic amoebae and that the importance of the individual T2S substrates varies in a host cell-specific fashion. Finally, it is now clear that novel T2S-dependent proteins that are specific to the genus Legionella are particularly important for L. pneumophila infection of key, environmental hosts.

Genomic characterization of a large outbreak of Legionella pneumophila serogroup 1 strains in Quebec City, 2012

During the summer of 2012, a major Legionella pneumophila serogroup 1 outbreak occurred in Quebec City, Canada, which caused 182 declared cases of Legionnaire's disease and included 13 fatalities. Legionella pneumophila serogroup 1 isolates from 23 patients as well as from 32 cooling towers located in the vicinity of the outbreak were recovered for analysis. In addition, 6 isolates from the 1996 Quebec City outbreak and 4 isolates from patients unrelated to both outbreaks were added to allow comparison. We characterized the isolates using pulsed-field gel electrophoresis, sequence-based typing, and whole genome sequencing. The comparison of patients-isolated strains to cooling tower isolates allowed the identification of the tower that was the source of the outbreak. Legionella pneumophila strain Quebec 2012 was identified as a ST-62 by sequence-based typing methodology. Two new Legionellaceae plasmids were found only in the epidemic strain. The LVH type IV secretion system was found in the 2012 outbreak isolates but not in the ones from the 1996 outbreak and only in half of the contemporary human isolates. The epidemic strains replicated more efficiently and were more cytotoxic to human macrophages than the environmental strains tested. At least four Icm/Dot effectors in the epidemic strains were absent in the environmental strains suggesting that some effectors could impact the intracellular replication in human macrophages. Sequence-based typing and pulsed-field gel electrophoresis combined with whole genome sequencing allowed the identification and the analysis of the causative strain including its likely environmental source.

Microbial diversities (16S and 18S rRNA gene pyrosequencing) and environmental pathogens within drinking water biofilms grown on the common premise plumbing materials unplasticized polyvinylchloride and copper

Drinking water (DW) biofilm communities influence the survival of opportunistic pathogens, yet knowledge about the microbial composition of DW biofilms developed on common in-premise plumbing material is limited. Utilizing 16S and 18S rRNA gene pyrosequencing, this study characterized the microbial community structure within DW biofilms established on unplasticized polyvinyl chloride (uPVC) and copper (Cu) surfaces and the impact of introducing Legionella pneumophila (Lp) and Acanthamoeba polyphaga. Mature (> 1 year old) biofilms were developed before inoculation with sterilized DW (control, Con), Lp, or Lp and A. polyphaga (LpAp). Comparison of uPVC and Cu biofilms indicated significant differences between bacterial (P = 0.001) and eukaryotic (P < 0.01) members attributable to the unique presence of several family taxa: Burkholderiaceae, Characeae, Epistylidae, Goniomonadaceae, Paramoebidae, Plasmodiophoridae, Plectidae, Sphenomonadidae, and Toxariaceae within uPVC biofilms; and Enterobacteriaceae, Erythrobacteraceae, Methylophilaceae, Acanthamoebidae, and Chlamydomonadaceae within Cu biofilms. Introduction of Lp alone or with A. polyphaga had no effect on bacterial community profiles (P > 0.05) but did affect eukaryotic members (uPVC, P < 0.01; Cu, P = 0.001). Thus, established DW biofilms host complex communities that may vary based on substratum matrix and maintain consistent bacterial communities despite introduction of Lp, an environmental pathogen.

Effect of GAC pre-treatment and disinfectant on microbial community structure and opportunistic pathogen occurrence

Opportunistic pathogens in potable water systems are an emerging health concern; however, the factors influencing their proliferation are poorly understood. Here we investigated the effects of prior granular activated carbon (GAC) biofiltration [GAC-filtered water, unfiltered water, and a blend (30% GAC filtered and 70% unfiltered water)] and disinfectant type (chlorine, chloramine) on opportunistic pathogen occurrence using five annular reactors (ARs) to simulate water distribution systems, particularly premise plumbing. GAC pre-treatment effectively reduced total organic carbon (TOC), resulting in three levels of influent TOC investigated. Quantitative polymerase chain reaction (q-PCR) provided molecular evidence of natural colonization of Legionella spp., Mycobacterium spp., Acanthamoeba spp., Hartmannella vermiformis and Mycobacterium avium on AR coupons. Cultivable mycobacteria and amoeba, including pathogenic species, were also found in bulk water and biofilm samples. While q-PCR tends to overestimate live cells, it provided a quantitative comparison of target organisms colonizing the AR biofilms in terms of gene copy numbers. In most cases, total bacteria and opportunistic pathogens were higher in the three undisinfected ARs, but the levels were not proportional to the level of GAC pre-treatment/TOC. Chlorine was more effective for controlling mycobacteria and Acanthamoeba, whereas chloramine was more effective for controlling Legionella. Both chlorine and chloramine effectively inhibited M. avium and H. vermiformis colonization. Pyrosequencing of 16S rRNA genes in coupon biofilms revealed a significant effect of GAC pre-treatment and disinfectant type on the microbial community structure. Overall, this study provides insights into the potential of different disinfectants and GAC biofilters at the treatment plant and in buildings to control downstream opportunistic pathogens and broader drinking water microbial communities.

Sub-femtomole detection of 16s rRNA from Legionella pneumophila using surface plasmon resonance imaging

Legionellosis has been and continues to be a life-threatening disease worldwide, even in developed countries. Given the severity and unpredictability of Legionellosis outbreaks, developing a rapid, highly specific, and sensitive detection method is thus of great pertinence. In this paper, we demonstrate that sub-femtomole levels of 16s rRNA from pathogenic Legionella pneumophila can be timely and effectively detected using an appropriate designed capture, detector probes, and a QD SPRi signal amplification strategy. To achieve specific and sensitive detection, optimal hybridization conditions and parameters were implemented. Among these parameters, fragmentation of the 16s rRNA and further signal amplification by QDs were found to be the main parameters contributing to signal enhancement. The appropriate design of the detector probes also increased the sensitivity of the detection system, mainly due to secondary structure of 16s rRNA. The use of 16s rRNA from L. pneumophila allowed for the detection of metabolically active pathogens with high sensitivity. Detection of 16s rRNA in solutions as diluted as 1 pM at 450 μL (0.45 femtomole) was achieved in less than 3h, making our approach suitable for the direct, timely, and effective detection of L. pneumophila within man-made water systems.

Multiple Legionella pneumophila Type II secretion substrates, including a novel protein, contribute to differential infection of the amoebae Acanthamoeba castellanii, Hartmannella vermiformis, and Naegleria lovaniensis

Type II protein secretion (T2S) by Legionella pneumophila is required for intracellular infection of host cells, including macrophages and the amoebae Acanthamoeba castellanii and Hartmannella vermiformis. Previous proteomic analysis revealed that T2S by L. pneumophila 130b mediates the export of >25 proteins, including several that appeared to be novel. Following confirmation that they are unlike known proteins, T2S substrates NttA, NttB, and LegP were targeted for mutation. nttA mutants were impaired for intracellular multiplication in A. castellanii but not H. vermiformis or macrophages, suggesting that novel exoproteins which are specific to Legionella are especially important for infection. Because the importance of NttA was host cell dependent, we examined a panel of T2S substrate mutants that had not been tested before in more than one amoeba. As a result, RNase SrnA, acyltransferase PlaC, and metalloprotease ProA all proved to be required for optimal intracellular multiplication in H. vermiformis but not A. castellanii. Further examination of an lspF mutant lacking the T2S apparatus documented that T2S is also critical for infection of the amoeba Naegleria lovaniensis. Mutants lacking SrnA, PlaC, or ProA, but not those deficient for NttA, were defective in N. lovaniensis. Based upon analysis of a double mutant lacking PlaC and ProA, the role of ProA in H. vermiformis was connected to its ability to activate PlaC, whereas in N. lovaniensis, ProA appeared to have multiple functions. Together, these data document that the T2S system exports multiple effectors, including a novel one, which contribute in different ways to the broad host range of L. pneumophila.

Legionellaand non-Legionellabacteria in a biological treatment plant

Legionella pneumophila were previously identified in the aeration ponds (up to 1010CFU/L) of a biological wastewater treatment plant at Borregaard Ind. Ltd., Sarpsborg, Norway, and in air samples (up to 3300 CFU/m3) collected above the aeration ponds. After 3 outbreaks of Legionnaires’ disease reported in this area in 2005 and 2008, the aeration ponds of the plant were shut down by the Norwegian authorities in September 2008. The aim of the present work was to analyze the Legionella and non-Legionella bacterial communities in the aeration ponds before and during the shutdown process and to identify potential human pathogens. The non-Legionella bacterial community was investigated in selected samples during the shutdown process by 16S rDNA sequencing of clone libraries (400 clones) and growth analysis. The concentration of L. pneumophila and Pseudomonas spp. DNA were monitored by quantitative PCR. Results showed a decrease in the concentration of L. pneumophila and Pseudomonas spp. during the shutdown. This was accompanied by a significant change in the composition of the bacterial community in the aeration ponds. This study demonstrated that several advanced analytical methods are necessary to characterize the bacterial population in complex environments, such as the industrial aeration ponds.

Type II secretion and Legionella virulence

Type II secretion (T2S) is one of six systems that can occur in Gram-negative bacteria for the purpose of secreting proteins into the extracellular milieu and/or into host cells. This chapter will describe the T2S system of Legionella pneumophila. Topics to be covered include the genetic basis of T2S in L. pneumophila, the numbers (>25), types, and novelties of Legionella proteins that are secreted via T2S, and the many ways in which T2S and its substrates promote L. pneumophila physiology, ecology, and virulence. Within the aquatic environment, T2S plays a major role in L. pneumophila intracellular infection of multiple types of (Acanthamoeba, Hartmannella, and Naegleria) amoebae. Within the mammalian host, T2S promotes bacterial persistence in lungs, intracellular infection of both macrophages and epithelial cells, and a dampening of the host innate immune response. In this context, T2S may represent a potential target for both industrial and biomedical application.

Anti-Legionella dumoffii activity of Galleria mellonella defensin and apolipophorin III

The gram-negative bacterium Legionella dumoffii is, beside Legionella pneumophila, an etiological agent of Legionnaires’ disease, an atypical form of pneumonia. The aim of this study was to determine the antimicrobial activity of Galleria mellonella defense polypeptides against L. dumoffii. The extract of immune hemolymph, containing a mixture of defense peptides and proteins, exhibited a dose-dependent bactericidal effect on L. dumoffii. The bacterium appeared sensitive to a main component of the hemolymph extract, apolipophorin III, as well as to a defense peptide, Galleria defensin, used at the concentrations 0.4 mg/mL and 40 μg/mL, respectively. L. dumoffii cells cultured in the presence of choline were more susceptible to both defense factors analyzed. A transmission electron microscopy study of bacterial cells demonstrated that Galleria defensin and apolipophorin III induced irreversible cell wall damage and strong intracellular alterations, i.e., increased vacuolization, cytoplasm condensation and the appearance of electron-white spaces in electron micrographs. Our findings suggest that insects, such as G. mellonella, with their great diversity of antimicrobial factors, can serve as a rich source of compounds for the testing of Legionella susceptibility to defense-related peptides and proteins.

Effects of disinfection on Legionella spp., eukarya, and biofilms in a hot water system

Legionella species are frequently detected in hot water systems, attached to the surface as a biofilm. In this work, the dynamics of Legionella spp. and diverse bacteria and eukarya associated together in the biofilm, coming from a pilot scale 1 system simulating a real hot water system, were investigated throughout 6 months after two successive heat shock treatments followed by three successive chemical treatments. Community structure was assessed by a fingerprint technique, single-strand conformation polymorphism (SSCP). In addition, the diversity and dynamics of Legionella and eukarya were investigated by small-subunit (SSU) ribosomal cloning and sequencing. Our results showed that pathogenic Legionella species remained after the heat shock and chemical treatments (Legionella pneumophila and Legionella anisa, respectively). The biofilm was not removed, and the bacterial community structure was transitorily affected by the treatments. Moreover, several amoebae had been detected in the biofilm before treatments (Thecamoebae sp., Vannella sp., and Hartmanella vermiformis) and after the first heat shock treatment, but only H. vermiformis remained. However, another protozoan affiliated with Alveolata, which is known as a host cell for Legionella, dominated the eukaryal species after the second heat shock and chemical treatment tests. Therefore, effective Legionella disinfection may be dependent on the elimination of these important microbial components. We suggest that eradicating Legionella in hot water networks requires better study of bacterial and eukaryal species associated with Legionella in biofilms.

Invasion of eukaryotic cells by Legionella pneumophila: A common strategy for all hosts?

Legionella pneumophila is an environmental micro-organism capable of producing an acute lobar pneumonia, commonly referred to as Legionnaires' disease, in susceptible humans. Legionellae are ubiquitous in aquatic environments, where they survive in biofilms or intracellularly in various protozoans. Susceptible humans become infected by breathing aerosols laden with the bacteria. The target cell for human infection is the alveolar macrophage, in which the bacteria abrogate phagolysosomal fusion. The remarkable ability of L pneumophila to infect a wide range of eukaryotic cells suggests a common strategy that exploits very fundamental cellular processes. The bacteria enter host cells via coiling phagocytosis and quickly subvert organelle trafficking events, leading to formation of a replicative phagosome in which the bacteria multiply. Vegetative growth continues for 8 to 10 h, after which the bacteria develop into a short, highly motile form called the 'mature form'. The mature form exhibits a thickening of the cell wall, stains red with the Gimenez stain, and is between 10 and 100 times more infectious than agar-grown bacteria. Following host cell lysis, the released bacteria infect other host cells, in which the mature form differentiates into a Gimenez-negative vegetative form, and the cycle begins anew. Virulence of L pneumophila is considered to be multifactorial, and there is growing evidence for both stage specific and sequential gene expression. Thus, L pneumophila may be a good model system for dissecting events associated with the host-parasite interactions.

Amoeba-related health risk in drinking water systems: could monitoring of amoebae be a complementary approach to current quality control strategies?

Culture-based methods for fecal indicator microorganisms are the standard protocol to assess potential health risk from drinking water systems. However, these traditional fecal indicators are inappropriate surrogates for disinfection-resistant fecal pathogens and the indigenous pathogens that grow in drinking water systems. There is now a range of molecular-based methods, such as quantitative PCR, which allow detection of a variety of pathogens and alternative indicators. Hence, in addition to targeting total Escherichia coli (i.e., dead and alive) for the detection of fecal pollution, various amoebae may be suitable to indicate the potential presence of pathogenic amoeba-resisting microorganisms, such as Legionellae. Therefore, monitoring amoeba levels by quantitative PCR could be a useful tool for directly and indirectly evaluating health risk and could also be a complementary approach to current microbial quality control strategies for drinking water systems.

Factors stimulating propagation of legionellae in cooling tower water

Our survey of cooling tower water demonstrated that the highest density of legionellae, >/=10 CFU/100 ml, appeared in water containing protozoa, >/=10 MPN/100 ml, and heterotrophic bacteria, >/=10 CFU/100 ml, at water temperatures between 25 and 35 degrees C. Viable counts of legionellae were detected even in the winter samples, and propagation, up to 10 CFU/100 ml, occurs in summer. The counts of legionellae correlated positively with increases in water temperature, pH, and protozoan counts, but not with heterotrophic bacterial counts. The water temperature of cooling towers may promote increases in the viable counts of legionellae, and certain microbes, e.g., protozoa or some heterotrophic bacteria, may be a factor stimulating the propagation of legionellae.

Gentamicin-Containing Peptone-Yeast Extract Medium for Cocultivation of Hartmannella vermiformis ATCC 50256 and Virulent Strains of Legionella pneumophila

We evaluated the use of peptone-yeast extract (PY) medium, different strains of Hartmannella vermiformis, and gentamicin in a coculture system to improve the discrimination of virulent and avirulent strains of Legionella pneumophila. H. vermiformis ATCC 50256 was unique among four strains of H. vermiformis, in that it multiplied equally well in Medium 1034 and PY medium (Medium 1034 without fetal calf serum, folic acid, hemin, and yeast nucleic acid and with a 50% reduction of peptone). However, both a virulent strain of L. pneumophila and its avirulent derivative strain multiplied in cocultures when PY medium was used. The multiplication of this avirulent strain was greatly reduced by incorporating gentamicin (1 (mu)g/ml) into the cocultivation system. Five virulent-avirulent sets of L. pneumophila strains were then tested for multiplication in cocultures with H. vermiformis ATCC 50256 and the gentamicin-containing PY medium. Only the virulent strains multiplied. The modified cocultivation system can discriminate between virulent and avirulent strains of L. pneumophila.

Development of a pilot-scale 1 for Legionella elimination in biofilm in hot water network: heat shock treatment evaluation

AIMS

(i) To develop an analytical tool in order to evaluate the effectiveness of anti-Legionella treatment in biofilm and (ii) study the fate of Legionella populations in water and biofilm after applying a heat shock treatment.

METHODS AND RESULTS

A pilot-scale unit simulating a hot water system was built and designed by the Scientific and Technical Building Centre (CSTB, France). At the end of the contamination period, a stable cultivable Legionella spp. concentration of 5x10(5) CFU l(-1) was obtained. Two heat shock treatments (70 degrees C for 30 min) were applied. The results showed that the first treatment had a transitional effect on the abatement of Legionella concentrations, while the second treatment had no detectable effect on Legionella populations in water and biofilm. The DAPI (4',6'-diamidino-2-phenylindole), Legionella PCR and GVPC (glycocolle vancomycin pyrophosphate cycloheximide) counts measured in the dead leg water of the Test Loop were 1, 2 and 2 log units higher than results found in the Test Loop water. Moreover, Legionella spp. count in tap water was about 10(4) GU l(-1). These analyses revealed that they are responsible for the rapid recolonization as well as the uncomplete destroyed biofilm. In addition, a resistance test was conducted and showed that Legionella in the second heat shock treatment was not thermo-resistant but thermo-acclimated.

CONCLUSION

Thermal disinfection does not seem to be efficient enough to eliminate Legionella when it is used as a curative treatment.

SIGNIFICANCE AND IMPACT OF THE STUDY

This work could help water managers for a better management of water network and for a better control of Legionella.

Experimental Legionella longbeachae infection in intratracheally inoculated mice

This study established an experimental model of replicative Legionella longbeachae infection in A/J mice. The animals were infected by intratracheal inoculation of 10(3)-10(9) c.f.u. L. longbeachae serogroup 1 (USA clinical isolates D4968, D4969 and D4973). The inocula of 10(9), 10(8), 10(7) and 10(6) c.f.u. of all tested L. longbeachae serogroup 1 isolates were lethal for A/J mice. Inoculation of 10(5) c.f.u. L. longbeachae caused death in 90 % of the animals within 5 days, whilst inoculation of 10(4) c.f.u. caused sporadic death of mice. All animals that received 10(3) c.f.u. bacteria developed acute lower respiratory disease, but were able to clear Legionella from the lungs within 3 weeks. The kinetics of bacterial growth in the lungs was independent of inoculum size and reached a growth peak about 3 logarithms above the initial inoculum at 72 h after inoculation. The most prominent histological changes in the lungs were observed at 48-72 h after inoculation in the form of a focal, neutrophil-dominant, peribronchiolar infiltration. The inflammatory process did not progress towards the interstitial or alveolar spaces. Immunohistological analyses revealed L. longbeachae serogroup 1 during the early phase of infection near the bronchiolar epithelia and later co-localized with inflammatory cells. BALB/c and C57BL/6 mice strains were also susceptible to infection with all L. longbeachae serogroup 1 strains tested and very similar changes were observed in the lungs of infected animals. These results underline the infection potential of L. longbeachae serogroup 1, which is associated with high morbidity and lethality in mice.

The use of copper and silver in carbon point-of-use filters for the suppression of Legionella throughput in domestic water systems

AIMS

To evaluate throughput of seeded Legionella pneumophila bacteria in domestic point-of-use filters.

METHODS AND RESULTS

The filters were challenged with tap water seeded with Leg. pneumophila. After multiple challenge events (4.25 x 10(11) CFU per filter), the levels of Legionella were lower in the effluent from the filter containing both copper and silver (mean 4.48 x 10(3) CFU ml(-1)) than in the effluent from the filter containing copper only (1.26 x 10(4) CFU ml(-1); P < 0.001). After a single challenge event of approx. 5 x 10(9) CFU L. pneumophila per filter, there was no significant difference between the levels of Legionella in the effluents from a carbon filter containing copper and a carbon filter with no metals (mean 6.87 x 10(2) and 6.89 x 10(2) CFU ml(-1), respectively; P = 0.985).

CONCLUSIONS

Legionella was detected in filter effluent up to 6 weeks after being challenged, indicating that while filters may reduce the levels during an initial contamination event, the exposure is extended as the accumulated bacteria slough off over time.

SIGNIFICANCE AND IMPACT OF THE STUDY

This study has provided an understanding of the response of Legionella to the use of silver and copper in domestic point-of-use carbon filters.

Early trafficking and intracellular replication of Legionella longbeachaea within an ER-derived late endosome-like phagosome

Legionella pneumophila is the predominant cause of Legionnaires' disease in the USA and Europe in contrast to Legionella longbeachaea, which is the leading cause of the disease in Western Australia. The ability of L. pneumophila to replicate intracellularly is triggered at the post-exponential phase along with expression of other virulence traits, such as motility. We show that while motility of L. longbeachaea is triggered upon growth transition into post-exponential phase, its ability to proliferate intracellularly is totally independent of the bacterial growth phase. Within macrophages, L. pneumophila replicates in a phagosome that excludes early and late endocytic markers and is surrounded by the rough endoplasmic reticulum (RER). In contrast, the L. longbeachaea phagosome colocalizes with the early endosomal marker early endosomal antigen 1 (EEA1) and the late endosomal markers lysosomal associated membrane glycoprotein 2 (LAMP-2) and mannose 6-phosphate receptor (M6PR), and is surrounded by the RER. The L. longbeachaea phagosome does not colocalize with the vacuolar ATPase (vATPase) proton pump, and the lysosomal luminal protease Cathepsin D, or the lysosomal tracer Texas red Ovalbumin (TROV). Intracellular proliferation of L. longbeachaea occurs in LAMP-2-positive phagosomes that are remodelled by the RER. Despite their distinct trafficking, both L. longbeachaea and L. pneumophila can replicate in communal phagosomes whose biogenesis is predominantly modulated by L. longbeachaea into LAMP-2-positive phagosomes. In addition, the L. pneumophila dotA mutant is rescued for intracellular replication if it co-inhabits the phagosome with L. longbeachaea. During late stages of infection, L. longbeachaea escape into the cytoplasm, prior to lysis of the macrophage, similar to L. pneumophila. We conclude that the L. longbeachaea phagosome matures to a non-acidified late endosome-like stage that is remodelled by the RER, indicating an idiosyncratic trafficking of L. longbeachaea compared with other intracellular pathogens, and a divergence in its intracellular lifestyle from L. pneumophila. In addition, re-routing biogenesis of the L. pneumophila phagosome into a late endosome controlled by L. longbeachaea has no effect on intracellular replication.

Effective proliferation of low level Legionella pneumophila serogroup 1 cells using coculture procedure with Acanthamoeba castellanii

The multiplications of low level Legionella pneumophila serogroup 1 cells by the coculture procedure with Acanthamoeba castellanii were tested in five strains. The cells in all strains proliferated effectively for isolating. This procedure might be a useful means of improving the successful isolation from environmental and clinical specimens of low level Legionella cells, and pursuing the source of infection.

Multiplication intra-amibienne de Legionella pneumophila et rôle potentiel des amibes dans la transmission de la légionellose

Legionnaires' disease is one of the major infectious risks related to hospital water systems. It is commonly accepted, that the disease is transmitted to man mostly by inhalation of water aerosols contaminated by Legionella pneumophila. The ability of L. pneumophila to multiply intracellularly within some amoebae better explains the ecology, the pathogenicity, and the virulence of this bacterium against human alveolar macrophages. The presence of these amoebae in water systems located where cases of Legionnaire's disease broke out, partly explains the difficulty in eradicating Legionella. Some studies also show that amoebae can play a major role in the transmission of the disease to man. Some other studies point out that inhaled amoebae could be involved in the pathogenesis of Legionnaire's disease. Future strategies to prevent the transmission of Legionella will probably have to include efficient treatments against amoebae.

The Icm/Dot type-IV secretion systems of Legionella pneumophila and Coxiella burnetii

Type-IV secretion systems are devices present in a wide range of bacteria (including bacterial pathogens) that deliver macromolecules (proteins and single-strand-DNA) across kingdom barriers (as well as between bacteria and into the surroundings). The type-IV secretion systems were divided into two subgroups and Legionella pneumophila and Coxiella burnetii are the only two bacteria known today to utilize a type-IVB secretion system for pathogenesis. In this review we summarized the available information concerning the icm/dot type-IVB secretion systems by comparing the two bacteria that possess this system, the proteins components of their systems as well as the homology of proteins from type-IVB secretion systems to proteins from type-IVA secretion systems. In addition, the phenotypes associated with mutants in the L. pneumophila icm/dot genes, their relations to properties of specific Icm/Dot proteins as well as the protein substrates delivered by this system are described.

Legionella pneumophila associated with the protozoan Hartmannella vermiformis in a model multi-species biofilm has reduced susceptibility to disinfectants

Legionella pneumophila will infect biofilm-associated protozoa, and in this way might be protected from disinfectants in potable water systems. A base biofilm containing Pseudomonas aeruginosa, Klebsiella pneumoniae, and Flavobacterium spp. was grown on steel coupons in potable water prior to the addition of L. pneumophila and the protozoan H. vermiformis. After 7 d, coupons were removed and treated with 0.5 mgl(-1) free residual chlorine (FRC) or 0.5 mgl(-1) monochloramine (MCA) for 15, 60, or 180 min or 24 h. In a second experiment, only L. pneumophila and the base biofilm organisms were present but with an identical treatment protocol. Treatment of L. pneumophila for 180 min in a system without H. vermiformis resulted in log reductions of 2.07 and 2.11 for FRC and MCA, respectively. When H. vermiformis was present, however, the treatment resulted in log reductions of 0.67 and 0.81 for FRC and MCA, respectively. A similar pattern was observed for 15 and 60 min contact times. These results indicate that L. pneumophila was less susceptible to MCA or FRC when associated with biofilm-associated H. vermiformis in a model potable water biofilm.

Intracellular proliferation of Legionella pneumophila in Hartmannella vermiformis in aquatic biofilms grown on plasticized polyvinyl chloride

The need for protozoa for the proliferation of Legionella pneumophila in aquatic habitats is still not fully understood and is even questioned by some investigators. This study shows the in vivo growth of L. pneumophila in protozoa in aquatic biofilms developing at high concentrations on plasticized polyvinyl chloride in a batch system with autoclaved tap water. The inoculum, a mixed microbial community including indigenous L. pneumophila originating from a tap water system, was added in an unfiltered as well as filtered (cellulose nitrate, 3.0-microm pore size) state. Both the attached and suspended biomasses were examined for their total amounts of ATP, for culturable L. pneumophila, and for their concentrations of protozoa. L. pneumophila grew to high numbers (6.3 log CFU/cm2) only in flasks with an unfiltered inoculum. Filtration obviously removed the growth-supporting factor, but it did not affect biofilm formation, as determined by measuring ATP. Cultivation, direct counting, and 18S ribosomal DNA-targeted PCR with subsequent sequencing revealed the presence of Hartmannella vermiformis in all flasks in which L. pneumophila multiplied and also when cycloheximide had been added. Fluorescent in situ hybridization clearly demonstrated the intracellular growth of L. pneumophila in trophozoites of H. vermiformis, with 25.9% +/- 10.5% of the trophozoites containing L. pneumophila on day 10 and >90% containing L. pneumophila on day 14. Calculations confirmed that intracellular growth was most likely the only way for L. pneumophila to proliferate within the biofilm. Higher biofilm concentrations, measured as amounts of ATP, gave higher L. pneumophila concentrations, and therefore the growth of L. pneumophila within engineered water systems can be limited by controlling biofilm formation.

Detection and identification of Legionella species from groundwaters

Legionellae are opportunistic bacterial pathogens causing Legionnaires' disease and Pontiac fever and are ubiquitous in surface waters and in infrastructure to contain or distribute water, including pipes, cooling towers, and whirlpool spas. Infection in community-acquired and nosocomial outbreaks is by exposure to contaminated aerosols. Little is known about the presence of legionellae in groundwater. This study used samples from various locations in the United States and Canada to determine if legionellae could be isolated from water and biofilms derived from groundwaters not known to be under the direct influence of surface water. Of the 114 total samples of water and biofilm tested, 29.1% and 28.2% were positive for Legionella by cultivation and polymerase chain reaction (PCR), respectively. Legionellae were found in both warm and colder groundwaters, with more isolates from samples incubated at 30 degrees C than the 35 degrees C conventional temperature for Legionella isolation. The concentration of Legionella found in the water samples ranged from 10(2) to 10(5) CFU/L and up to 1.2 x 10(2) CFU/cm(2) in the biofilm. The species of Legionella identified included both known pathogenic species and species that have not yet been identified as human pathogens. Millions of people in Canada, and around the world, rely on groundwater as their source for drinking. This study shows that legionellae are widespread in groundwater and have the potential to seed derived water supplies and biofilms in public distribution systems. This further widens the known sphere of Legionella colonization and the implications of its presence for public health.