Satellite growth of Legionella pneumophila with an environmental isolate of Flavobacterium breve

Legionella colonization and 3D spatial location within a Pseudomonas biofilm

Biofilms are known to be critical for Legionella settlement in engineered water systems and are often associated with Legionnaire's Disease events. One of the key features of biofilms is their heterogeneous three-dimensional structure which supports the establishment of microbial interactions and confers protection to microorganisms. This work addresses the impact of Legionella pneumophila colonization of a Pseudomonas fluorescens biofilm, as information about the interactions between Legionella and biofilm structures is scarce. It combines a set of meso- and microscale biofilm analyses (Optical Coherence Tomography, Episcopic Differential Interference Contrast coupled with Epifluorescence Microscopy and Confocal Laser Scanning Microscopy) with PNA-FISH labelled L. pneumophila to tackle the following questions: (a) does the biofilm structure change upon L. pneumophila biofilm colonization?; (b) what happens to L. pneumophila within the biofilm over time and (c) where is L. pneumophila preferentially located within the biofilm? Results showed that P. fluorescens structure did not significantly change upon L. pneumophila colonization, indicating the competitive advantage of the first colonizer. Imaging of PNA-labelled L. pneumophila showed that compared to standard culture recovery it colonized to a greater extent the 3-day-old P. fluorescens biofilms, presumably entering in VBNC state by the end of the experiment. L. pneumophila was mostly located in the bottom regions of the biofilm, which is consistent with the physiological requirements of both bacteria and confers enhanced Legionella protection against external aggressions. The present study provides an expedited methodological approach to address specific systematic laboratory studies concerning the interactions between L. pneumophila and biofilm structure that can provide, in the future, insights for public health Legionella management of water systems.

Host-bacteria interactions: ecological and evolutionary insights from ancient, professional endosymbionts

Interactions between eukaryotic hosts and their bacterial symbionts drive key ecological and evolutionary processes, from regulating ecosystems to the evolution of complex molecular machines and processes. Over time, endosymbionts generally evolve reduced genomes, and their relationship with their host tends to stabilize. However, host-bacteria relationships may be heavily influenced by environmental changes. Here, we review these effects on one of the most ancient and diverse endosymbiotic groups, formed by-among others-Legionellales, Francisellaceae, and Piscirickettsiaceae. This group is referred to as Deep-branching Intracellular Gammaproteobacteria (DIG), whose last common ancestor presumably emerged about 2 Ga ago. We show that DIGs are globally distributed, but generally at very low abundance, and are mainly identified in aquatic biomes. Most DIGs harbour a type IVB secretion system, critical for host-adaptation, but its structure and composition vary. Finally, we review the different types of microbial interactions that can occur in diverse environments, with direct or indirect effects on DIG populations. The increased use of omics technologies on environmental samples will allow a better understanding of host-bacterial interactions and help unravel the definition of DIGs as a group from an ecological, molecular, and evolutionary perspective.

Ecology of Legionella pneumophila biofilms: The link between transcriptional activity and the biphasic cycle

There has been considerable discussion regarding the environmental life cycle of Legionella pneumophila and its virulence potential in natural and man-made water systems. On the other hand, the bacterium's morphogenetic mechanisms within host cells (amoeba and macrophages) have been well documented and are linked to its ability to transition from a non-virulent, replicative state to an infectious, transmissive state. Although the morphogenetic mechanisms associated with the formation and detachment of the L. pneumophila biofilm have also been described, the capacity of the bacteria to multiply extracellularly is not generally accepted. However, several studies have shown genetic pathways within the biofilm that resemble intracellular mechanisms. Understanding the functionality of L. pneumophila cells within a biofilm is fundamental for assessing the ecology and evaluating how the biofilm architecture influences L. pneumophila survival and persistence in water systems. This manuscript provides an overview of the biphasic cycle of L. pneumophila and its implications in associated intracellular mechanisms in amoeba. It also examines the molecular pathways and gene regulation involved in L. pneumophila biofilm formation and dissemination. A holistic analysis of the transcriptional activities in L. pneumophila biofilms is provided, combining the information of intracellular mechanisms in a comprehensive outline. Furthermore, this review discusses the techniques that can be used to study the morphogenetic states of the bacteria within biofilms, at the single cell and population levels.

Legionella relative abundance in shower hose biofilms is associated with specific microbiome members

Legionella are natural inhabitants of building plumbing biofilms, where interactions with other microorganisms influence their survival, proliferation, and death. Here, we investigated the associations of Legionella with bacterial and eukaryotic microbiomes in biofilm samples extracted from 85 shower hoses of a multiunit residential building. Legionella spp. relative abundance in the biofilms ranged between 0-7.8%, of which only 0-0.46% was L. pneumophila. Our data suggest that some microbiome members were associated with high (e.g. Chthonomonas, Vrihiamoeba) or low (e.g. Aquabacterium, Vannella) Legionella relative abundance. The correlations of the different Legionella variants (30 Zero-Radius OTUs detected) showed distinct patterns, suggesting separate ecological niches occupied by different Legionella species. This study provides insights into the ecology of Legionella with respect to: (i) the colonization of a high number of real shower hoses biofilm samples; (ii) the ecological meaning of associations between Legionella and co-occurring bacterial/eukaryotic organisms; (iii) critical points and future directions of microbial-interaction-based-ecological-investigations.

Toxoflavin secreted by Pseudomonas alcaliphila inhibits the growth of Legionella pneumophila and Vermamoeba vermiformis

Legionella pneumophila is a natural inhabitant of water systems. From there, it can be transmitted to humans by aerosolization resulting in severe pneumonia. Most large outbreaks are caused by cooling towers colonized with L. pneumophila. The resident microbiota of the cooling tower is a key determinant for the colonization and growth of L. pneumophila. In our preceding study, the genus Pseudomonas correlated negatively with the presence of L. pneumophila in cooling towers, but it was not clear which species was responsible. Therefore, we identified the Pseudomonas species inhabiting 14 cooling towers using a Pseudomonas-specific 16S rRNA amplicon sequencing strategy. We found that cooling towers that are free of L. pneumophila contained a high relative abundance of members from the Pseudomonas alcaliphila/oleovorans phylogenetic cluster. P. alcaliphila JCM 10630 inhibited the growth of L. pneumophila on agar plates. Analysis of the P. alcaliphila genome revealed the presence of a gene cluster predicted to produce toxoflavin. L. pneumophila growth was inhibited by pure toxoflavin and by extracts from P. alcaliphila culture found to contain toxoflavin by liquid chromatography coupled with mass spectrometry. In addition, toxoflavin inhibits the growth of Vermameoba vermiformis, a host cell of L. pneumophila. Our study indicates that P. alcaliphila may be important to restrict growth of L. pneumophila in water systems through the production of toxoflavin. A sufficiently high concentration of toxoflavin is likely not achieved in the bulk water but might have a local inhibitory effect such as near or in biofilms.

Bacterial Antagonistic Species of the Pathogenic Genus Legionella Isolated from Cooling Tower

Legionella pneumophila is the causative agent of Legionnaires' disease, a severe pneumonia. Cooling towers are a major source of large outbreaks of the disease. The growth of L. pneumophila in these habitats is influenced by the resident microbiota. Consequently, the aim of this study was to isolate and characterize bacterial species from cooling towers capable of inhibiting several strains of L. pneumophila and one strain of L. quinlivanii. Two cooling towers were sampled to isolate inhibiting bacterial species. Seven inhibitory isolates were isolated, through serial dilution plating and streaking on agar plates, belonging to seven distinct species. The genomes of these isolates were sequenced to identify potential genetic elements that could explain the inhibitory effect. The results showed that the bacterial isolates were taxonomically diverse and that one of the isolates may be a novel species. Genome analysis showed a high diversity of antimicrobial gene products identified in the genomes of the bacterial isolates. Finally, testing different strains of Legionella demonstrated varying degrees of susceptibility to the antimicrobial activity of the antagonistic species. This may be due to genetic variability between the Legionella strains. The results demonstrate that though cooling towers are breeding grounds for L. pneumophila, the bacteria must contend with various antagonistic species. Potentially, these species could be used to create an inhospitable environment for L. pneumophila, and thus decrease the probability of outbreaks occurring.

Legionella and Biofilms-Integrated Surveillance to Bridge Science and Real-Field Demands

Legionella is responsible for the life-threatening pneumonia commonly known as Legionnaires’ disease or legionellosis. Legionellosis is known to be preventable if proper measures are put into practice. Despite the efforts to improve preventive approaches, Legionella control remains one of the most challenging issues in the water treatment industry. Legionellosis incidence is on the rise and is expected to keep increasing as global challenges become a reality. This puts great emphasis on prevention, which must be grounded in strengthened Legionella management practices. Herein, an overview of field-based studies (the system as a test rig) is provided to unravel the common roots of research and the main contributions to Legionella’s understanding. The perpetuation of a water-focused monitoring approach and the importance of protozoa and biofilms will then be discussed as bottom-line questions for reliable Legionella real-field surveillance. Finally, an integrated monitoring model is proposed to study and control Legionella in water systems by combining discrete and continuous information about water and biofilm. Although the successful implementation of such a model requires a broader discussion across the scientific community and practitioners, this might be a starting point to build more consistent Legionella management strategies that can effectively mitigate legionellosis risks by reinforcing a pro-active Legionella prevention philosophy.

Unravelling the importance of the eukaryotic and bacterial communities and their relationship with Legionella spp. ecology in cooling towers: a complex network

BACKGROUND

Cooling towers are a major source of large community-associated outbreaks of Legionnaires' disease, a severe pneumonia. This disease is contracted when inhaling aerosols that are contaminated with bacteria from the genus Legionella, most importantly Legionella pneumophila. How cooling towers support the growth of this bacterium is still not well understood. As Legionella species are intracellular parasites of protozoa, it is assumed that protozoan community in cooling towers play an important role in Legionella ecology and outbreaks. However, the exact mechanism of how the eukaryotic community contributes to Legionella ecology is still unclear. Therefore, we used 18S rRNA gene amplicon sequencing to characterize the eukaryotic communities of 18 different cooling towers. The data from the eukaryotic community was then analysed with the bacterial community of the same towers in order to understand how each community could affect Legionella spp. ecology in cooling towers.

RESULTS

We identified several microbial groups in the cooling tower ecosystem associated with Legionella spp. that suggest the presence of a microbial loop in these systems. Dissolved organic carbon was shown to be a major factor in shaping the eukaryotic community and may be an important factor for Legionella ecology. Network analysis, based on co-occurrence, revealed that Legionella was correlated with a number of different organisms. Out of these, the bacterial genus Brevundimonas and the ciliate class Oligohymenophorea were shown, through in vitro experiments, to stimulate the growth of L. pneumophila through direct and indirect mechanisms.

CONCLUSION

Our results suggest that Legionella ecology depends on the host community, including ciliates and on several groups of organisms that contribute to its survival and growth in the cooling tower ecosystem. These findings further support the idea that some cooling tower microbiomes may promote the survival and growth of Legionella better than others. Video Abstract.

Legionella Diversity and Spatiotemporal Variation in The Occurrence of Opportunistic Pathogens within a Large Building Water System

Understanding Legionella survival mechanisms within building water systems (BWSs) is challenging due to varying engineering, operational, and water quality characteristics unique to each system. This study aimed to evaluate Legionella, mycobacteria, and free-living amoebae occurrence within a BWS over 18-28 months at six locations differing in plumbing material and potable water age, quality, and usage. A total of 114 bulk water and 57 biofilm samples were analyzed. Legionella culturability fluctuated seasonally with most culture-positive samples being collected during the winter compared to the spring, summer, and fall months. Positive and negative correlations between Legionella and L. pneumophila occurrence and other physiochemical and microbial water quality parameters varied between location and sample types. Whole genome sequencing of 19 presumptive Legionella isolates, from four locations across three time points, identified nine isolates as L. pneumophila serogroup (sg) 1 sequence-type (ST) 1; three as L. pneumophila sg5 ST1950 and ST2037; six as L. feeleii; and one as Ochrobactrum. Results showed the presence of a diverse Legionella population with consistent and sporadic occurrence at four and two locations, respectively. Viewed collectively with similar studies, this information will enable a better understanding of the engineering, operational, and water quality parameters supporting Legionella growth within BWSs.

Impact of temperature on Legionella pneumophila, its protozoan host cells, and the microbial diversity of the biofilm community of a pilot cooling tower

Legionella pneumophila is a waterborne bacterium known for causing Legionnaires' Disease, a severe pneumonia. Cooling towers are a major source of outbreaks, since they provide ideal conditions for L. pneumophila growth and produce aerosols. In such systems, L. pneumophila typically grow inside protozoan hosts. Several abiotic factors such as water temperature, pipe material and disinfection regime affect the colonization of cooling towers by L. pneumophila. The local physical and biological factors promoting the growth of L. pneumophila in water systems and its spatial distribution are not well understood. Therefore, we built a lab-scale cooling tower to study the dynamics of L. pneumophila colonization in relationship to the resident microbiota and spatial distribution. The pilot was filled with water from an operating cooling tower harboring low levels of L. pneumophila. It was seeded with Vermamoeba vermiformis, a natural host of L. pneumophila, and then inoculated with L. pneumophila. After 92 days of operation, the pilot was disassembled, the water was collected, and biofilm was extracted from the pipes. The microbiome was studied using 16S rRNA and 18S rRNA genes amplicon sequencing. The communities of the water and of the biofilm were highly dissimilar. The relative abundance of Legionella in water samples reached up to 11% whereas abundance in the biofilm was extremely low (≤0.5%). In contrast, the host cells were mainly present in the biofilm. This suggests that L. pneumophila grows in host cells associated with biofilm and is then released back into the water following host cell lysis. In addition, water temperature shaped the bacterial and eukaryotic community of the biofilm, indicating that different parts of the systems may have different effects on Legionella growth.

Presence of Legionella spp. in cooling towers: the role of microbial diversity, Pseudomonas, and continuous chlorine application

Legionnaires' disease (LD) is a severe pneumonia caused by several species of the genus Legionella, most frequently by Legionella pneumophila. Cooling towers are the most common source for large community-associated outbreaks. Colonization, survival, and proliferation of L. pneumophila in cooling towers are necessary for outbreaks to occur. These steps are affected by the chemical and physical parameters of the cooling tower environment. We hypothesize that the bacterial community residing in the cooling tower could also affect the presence of L. pneumophila. A 16S rRNA gene targeted amplicon sequencing approach was used to study the bacterial community of cooling towers and its relationship with the Legionella spp. and L. pneumophila communities. The results indicated that the water source shaped the bacterial community of cooling towers. Several taxa were enriched and positively correlated with Legionella spp. and L. pneumophila. In contrast, Pseudomonas showed a strong negative correlation with Legionella spp. and several other genera. Most importantly, continuous chlorine application reduced microbial diversity and promoted the presence of Pseudomonas creating a non-permissive environment for Legionella spp. This suggests that disinfection strategies as well as the resident microbial population influences the ability of Legionella spp. to colonize cooling towers.

Exploiting the Richness of Environmental Waterborne Bacterial Species to Find Natural Legionella pneumophila Competitors

Legionella pneumophila is one of the most tracked waterborne pathogens and remains an important threat to human health. Despite the use of biocides, L. pneumophila is able to persist in engineered water systems with the help of multispecies biofilms and phagocytic protists. For few years now, high-throughput sequencing methods have enabled a better understanding of microbial communities in freshwater environments. Those unexplored and complex communities compete for nutrients using antagonistic molecules as war weapons. Up to now, few of these molecules were characterized in regards of L. pneumophila sensitivity. In this context, we established, from five freshwater environments, a vast collection of culturable bacteria and investigated their ability to inhibit the growth of L. pneumophila. All bacterial isolates were classified within 4 phyla, namely Proteobacteria (179/273), Bacteroidetes (48/273), Firmicutes (43/273), and Actinobacteria (3/273) according to 16S rRNA coding sequences. Aeromonas, Bacillus, Flavobacterium, and Pseudomonas were the most abundant genera (154/273). Among the 273 isolates, 178 (65.2%) were shown to be active against L. pneumophila including 137 isolates of the four previously cited main genera. Additionally, other less represented genera depicted anti-Legionella activity such as Acinetobacter, Kluyvera, Rahnella, or Sphingobacterium. Furthermore, various inhibition diameters were observed among active isolates, ranging from 0.4 to 9 cm. Such variability suggests the presence of numerous and diverse natural compounds in the microenvironment of L. pneumophila. These molecules include both diffusible secreted compounds and volatile organic compounds, the latter being mainly produced by Pseudomonas strains. Altogether, this work sheds light on unexplored freshwater bacterial communities that could be relevant for the biological control of L. pneumophila in manmade water systems.

Disintegration of simulated drinking water biofilms with arrays of microchannel plasma jets

Biofilms exist and thrive within drinking water distribution networks, and can present human health concerns. Exposure of simulated drinking water biofilms, grown from groundwater, to a 9 × 9 array of microchannel plasma jets has the effect of severely eroding the biofilm and deactivating the organisms they harbor. In-situ measurements of biofilm structure and thickness with an optical coherence tomography (OCT) system show the biofilm thickness to fall from 122 ± 17 µm to 55 ± 13 µm after 15 min. of exposure of the biofilm to the microplasma column array, when the plasmas are dissipating a power density of 58 W/cm². All biofilms investigated vanish with 20 min. of exposure. Confocal laser scanning microscopy (CLSM) demonstrates that the number of living cells in the biofilms declines by more than 93% with 15 min. of biofilm exposure to the plasma arrays. Concentrations of several oxygen-bearing species, generated by the plasma array, were found to be 0.4–21 nM/s for the hydroxyl radical (OH), 85–396 nM/s for the ¹O₂ excited molecule, 98–280 µM for H₂O₂, and 24–42 µM for O₃ when the power density delivered to the array was varied between 3.6 W/cm² and 79 W/cm². The data presented here demonstrate the potential of microplasma arrays as a tool for controlling, through non-thermal disruption and removal, mixed-species biofilms prevalent in commercial and residential water systems.

Biofilms in drinking water premise plumbing systems can be disrupted and their microorganisms deactivated by exposure to jets of ionized gas known as plasma. Researchers at the University of Illinois, USA, led by Thanh (Helen) Nguyen and J. Gary Eden, explored the potential of low temperature plasma jets in disrupting & removing drinking water biofilms. The plasma was directed through fabricated microchannels and onto samples that the simulated biofilms. The interaction of the plasma with air and water generated reactive chemical species and ultraviolet radiation that disrupted the biofilms and deactivated the microorganisms within them. The biofilms studied vanished within 20 min. of plasma exposure. Plasma jets offer an inexpensive, low temperature and chlorine-free method for combating harmful biofilms in drinking water premise plumbing systems.

Microbial Ecology and Water Chemistry Impact Regrowth of Opportunistic Pathogens in Full-Scale Reclaimed Water Distribution Systems

Need for global water security has spurred growing interest in wastewater reuse to offset demand for municipal water. While reclaimed (i.e., nonpotable) microbial water quality regulations target fecal indicator bacteria, opportunistic pathogens (OPs), which are subject to regrowth in distribution systems and spread via aerosol inhalation and other noningestion routes, may be more relevant. This study compares the occurrences of five OP gene markers ( Acanthamoeba spp., Legionella spp., Mycobacterium spp., Naegleria fowleri, Pseudomonas aeruginosa) in reclaimed versus potable water distribution systems and characterizes factors potentially contributing to their regrowth. Samples were collected over four sampling events at the point of compliance for water exiting treatment plants and at five points of use at four U.S. utilities bearing both reclaimed and potable water distribution systems. Reclaimed water systems harbored unique water chemistry (e.g., elevated nutrients), microbial community composition, and OP occurrence patterns compared to potable systems examined here and reported in the literature. Legionella spp. genes, Mycobacterium spp. genes, and total bacteria, represented by 16S rRNA genes, were more abundant in reclaimed than potable water distribution system samples ( p ≤ 0.0001). This work suggests that further consideration should be given to managing reclaimed water distribution systems with respect to nonpotable exposures to OPs.

Factors Mediating Environmental Biofilm Formation by Legionella pneumophila

Legionella pneumophila (L. pneumophila) is an opportunistic waterborne pathogen and the causative agent for Legionnaires' disease, which is transmitted to humans via inhalation of contaminated water droplets. The bacterium is able to colonize a variety of man-made water systems such as cooling towers, spas, and dental lines and is widely distributed in multiple niches, including several species of protozoa In addition to survival in planktonic phase, L. pneumophila is able to survive and persist within multi-species biofilms that cover surfaces within water systems. Biofilm formation by L. pneumophila is advantageous for the pathogen as it leads to persistence, spread, resistance to treatments and an increase in virulence of this bacterium. Furthermore, Legionellosis outbreaks have been associated with the presence of L. pneumophila in biofilms, even after the extensive chemical and physical treatments. In the microbial consortium-containing L. pneumophila among other organisms, several factors either positively or negatively regulate the presence and persistence of L. pneumophila in this bacterial community. Biofilm-forming L. pneumophila is of a major importance to public health and have impact on the medical and industrial sectors. Indeed, prevention and removal protocols of L. pneumophila as well as diagnosis and hospitalization of patients infected with this bacteria cost governments billions of dollars. Therefore, understanding the biological and environmental factors that contribute to persistence and physiological adaptation in biofilms can be detrimental to eradicate and prevent the transmission of L. pneumophila. In this review, we focus on various factors that contribute to persistence of L. pneumophila within the biofilm consortium, the advantages that the bacteria gain from surviving in biofilms, genes and gene regulation during biofilm formation and finally challenges related to biofilm resistance to biocides and anti-Legionella treatments.

From Many Hosts, One Accidental Pathogen: The Diverse Protozoan Hosts of Legionella

The 1976 outbreak of Legionnaires' disease led to the discovery of the intracellular bacterial pathogen Legionella pneumophila. Given their impact on human health, Legionella species and the mechanisms responsible for their replication within host cells are often studied in alveolar macrophages, the primary human cell type associated with disease. Despite the potential severity of individual cases of disease, Legionella are not spread from person-to-person. Thus, from the pathogen's perspective, interactions with human cells are accidents of time and space—evolutionary dead ends with no impact on Legionella's long-term survival or pathogenic trajectory. To understand Legionella as a pathogen is to understand its interaction with its natural hosts: the polyphyletic protozoa, a group of unicellular eukaryotes with a staggering amount of evolutionary diversity. While much remains to be understood about these enigmatic hosts, we summarize the current state of knowledge concerning Legionella's natural host range, the diversity of Legionella-protozoa interactions, the factors influencing these interactions, the importance of avoiding the generalization of protozoan-bacterial interactions based on a limited number of model hosts and the central role of protozoa to the biology, evolution, and persistence of Legionella in the environment.

Rapid and reliable identification of waterborne Legionella species by MALDI-TOF mass spectrometry

Detection and enumeration of Legionella bacteria in drinking water is regulated in Germany by ISO 11731-2. The mandatory method for species identification employs parallel subculturing of suspicious colonies on selective media requiring the handling of a large number of cultivation plates. After changes to the drinking water quality regulation in Germany in 2012 the demand for Legionella contamination testing increased drastically. A more reliable, faster and less laborious method for species identification is therefore desirable. Matrix-assisted laser desorption ionization followed by time of flight detection mass spectrometry (MALDI-TOF MS) promises an accelerated identification of bacteria with high reliability and reduced expenditure. Our study shows that MS-based species identification results are in full concordance with cultural and biochemical detection and differentiation and that valuable additional information can be gained, even though the ISO regulation demands an extended incubation period for primary bacterial cultures that is actually in contrast to the prerequisites of the MALDI Biotyper system. In addition, the established identification algorithm is very economical and improves time-to-result. Based on our findings, the amendment of MALID-TOF MS identification to ISO11731-2 as an alternative identification method should be taken into consideration.

Response of Simulated Drinking Water Biofilm Mechanical and Structural Properties to Long-Term Disinfectant Exposure

Mechanical and structural properties of biofilms influence the accumulation and release of pathogens in drinking water distribution systems (DWDS). Thus, understanding how long-term residual disinfectants exposure affects biofilm mechanical and structural properties is a necessary aspect for pathogen risk assessment and control. In this study, elastic modulus and structure of groundwater biofilms was monitored by atomic force microscopy (AFM) and optical coherence tomography (OCT) during three months of exposure to monochloramine or free chlorine. After the first month of disinfectant exposure, the mean stiffness of monochloramine- or free-chlorine-treated biofilms was 4 to 9 times higher than those before treatment. Meanwhile, the biofilm thickness decreased from 120 ± 8 μm to 93 ± 6-107 ± 11 μm. The increased surface stiffness and decreased biofilm thickness within the first month of disinfectant exposure was presumably due to the consumption of biomass. However, by the second to third month during disinfectant exposure, the biofilm mean stiffness showed a 2- to 4-fold decrease, and the biofilm thickness increased to 110 ± 7-129 ± 8 μm, suggesting that the biofilms adapted to disinfectant exposure. After three months of the disinfectant exposure process, the disinfected biofilms showed 2-5 times higher mean stiffness (as determined by AFM) and 6-13-fold higher ratios of protein over polysaccharide, as determined by differential staining and confocal laser scanning microscopy (CLSM), than the nondisinfected groundwater biofilms. However, the disinfected biofilms and nondisinfected biofilms showed statistically similar thicknesses (t test, p > 0.05), suggesting that long-term disinfection may not significantly remove net biomass. This study showed how biofilm mechanical and structural properties vary in response to a complex DWDS environment, which will contribute to further research on the risk assessment and control of biofilm-associated-pathogens in DWDS.

Role of biofilm roughness and hydrodynamic conditions in Legionella pneumophila adhesion to and detachment from simulated drinking water biofilms

Biofilms in drinking water distribution systems (DWDS) could exacerbate the persistence and associated risks of pathogenic Legionella pneumophila (L. pneumophila), thus raising human health concerns. However, mechanisms controlling adhesion and subsequent detachment of L. pneumophila associated with biofilms remain unclear. We determined the connection between L. pneumophila adhesion and subsequent detachment with biofilm physical structure characterization using optical coherence tomography (OCT) imaging technique. Analysis of the OCT images of multispecies biofilms grown under low nutrient condition up to 34 weeks revealed the lack of biofilm deformation even when these biofilms were exposed to flow velocity of 0.7 m/s, typical flow for DWDS. L. pneumophila adhesion on these biofilm under low flow velocity (0.007 m/s) positively correlated with biofilm roughness due to enlarged biofilm surface area and local flow conditions created by roughness asperities. The preadhered L. pneumophila on selected rough and smooth biofilms were found to detach when these biofilms were subjected to higher flow velocity. At the flow velocity of 0.1 and 0.3 m/s, the ratio of detached cell from the smooth biofilm surface was from 1.3 to 1.4 times higher than that from the rough biofilm surface, presumably because of the low shear stress zones near roughness asperities. This study determined that physical structure and local hydrodynamics control L. pneumophila adhesion to and detachment from simulated drinking water biofilm, thus it is the first step toward reducing the risk of L. pneumophila exposure and subsequent infections.

Influence of copper surfaces on biofilm formation by Legionella pneumophila in potable water

Legionella pneumophila is a waterborne pathogen that can cause Legionnaires' disease, a fatal pneumonia, or Pontiac fever, a mild form of disease. Copper is an antimicrobial material used for thousands of years. Its incorporation in several surface materials to control the transmission of pathogens has been gaining importance in the past decade. In this work, the ability of copper to control the survival of L. pneumophila in biofilms was studied. For that, the incorporation of L. pneumophila in polymicrobial drinking water biofilms formed on copper, PVC and PEX, and L. pneumophila mono-species biofilms formed on copper and uPVC were studied by comparing cultivable and total numbers (quantified by peptide nucleic acid (PNA) hybridisation). L. pneumophila was never recovered by culture from heterotrophic biofilms; however, PNA-positive numbers were slightly higher in biofilms formed on copper (5.9 × 10(5) cells cm(-2)) than on PVC (2.8 × 10(5) cells cm(-2)) and PEX (1.7 × 10(5) cells cm(-2)). L. pneumophila mono-species biofilms grown on copper gave 6.9 × 10(5) cells cm(-2) for PNA-positive cells and 4.8 × 10(5) CFU cm(-2) for cultivable numbers, showing that copper is not directly effective in killing L. pneumophila. Therefore previous published studies showing inactivation of L. pneumophila by copper surfaces in potable water polymicrobial species biofilms must be carefully interpreted.

The many forms of a pleomorphic bacterial pathogen-the developmental network of Legionella pneumophila

Legionella pneumophila is a natural intracellular bacterial parasite of free-living freshwater protozoa and an accidental human pathogen that causes Legionnaires' disease. L. pneumophila differentiates, and does it in style. Recent experimental data on L. pneumophila's differentiation point at the existence of a complex network that involves many developmental forms. We intend readers to: (i) understand the biological relevance of L. pneumophila's forms found in freshwater and their potential to transmit Legionnaires' disease, and (ii) learn that the common depiction of L. pneumophila's differentiation as a biphasic developmental cycle that alternates between a replicative and a transmissive form is but an oversimplification of the actual process. Our specific objectives are to provide updates on the molecular factors that regulate L. pneumophila's differentiation (Section The Differentiation Process and Its Regulation), and describe the developmental network of L. pneumophila (Section Dissecting Lp's Developmental Network), which for clarity's sake we have dissected into five separate developmental cycles. Finally, since each developmental form seems to contribute differently to the human pathogenic process and the transmission of Legionnaires' disease, readers are presented with a challenge to develop novel methods to detect the various L. pneumophila forms present in water (Section Practical Implications), as a means to improve our assessment of risk and more effectively prevent legionellosis outbreaks.

Effect of disinfectant, water age, and pipe materials on bacterial and eukaryotic community structure in drinking water biofilm

Availability of safe, pathogen-free drinking water is vital to public health; however, it is impossible to deliver sterile drinking water to consumers. Recent microbiome research is bringing new understanding to the true extent and diversity of microbes that inhabit water distribution systems. The purpose of this study was to determine how water chemistry in main distribution lines shape the microbiome in drinking water biofilms and to explore potential associations between opportunistic pathogens and indigenous drinking water microbes. Effects of disinfectant (chloramines, chlorine), water age (2.3 days, 5.7 days), and pipe material (cement, iron, PVC) were compared in parallel triplicate simulated water distribution systems. Pyrosequencing was employed to characterize bacteria and terminal restriction fragment polymorphism was used to profile both bacteria and eukaryotes inhabiting pipe biofilms. Disinfectant and water age were both observed to be strong factors in shaping bacterial and eukaryotic community structures. Pipe material only influenced the bacterial community structure (ANOSIM test, P < 0.05). Interactive effects of disinfectant, pipe material, and water age on both bacteria and eukaryotes were noted. Disinfectant concentration had the strongest effect on bacteria, while dissolved oxygen appeared to be a major driver for eukaryotes (BEST test). Several correlations of similarity metrics among populations of bacteria, eukaryotes, and opportunistic pathogens, as well as one significant association between mycobacterial and proteobacterial operational taxonomic units, provides insight into means by which manipulating the microbiome may lead to new avenues for limiting the growth of opportunistic pathogens (e.g., Legionella) or other nuisance organisms (e.g., nitrifiers).

Biofilms: the stronghold of Legionella pneumophila

Legionellosis is mostly caused by Legionella pneumophila and is defined as a severe respiratory illness with a case fatality rate ranging from 5% to 80%. L. pneumophila is ubiquitous in natural and anthropogenic water systems. L. pneumophila is transmitted by inhalation of contaminated aerosols produced by a variety of devices. While L. pneumophila replicates within environmental protozoa, colonization and persistence in its natural environment are also mediated by biofilm formation and colonization within multispecies microbial communities. There is now evidence that some legionellosis outbreaks are correlated with the presence of biofilms. Thus, preventing biofilm formation appears as one of the strategies to reduce water system contamination. However, we lack information about the chemical and biophysical conditions, as well as the molecular mechanisms that allow the production of biofilms by L. pneumophila. Here, we discuss the molecular basis of biofilm formation by L. pneumophila and the roles of other microbial species in L. pneumophila biofilm colonization. In addition, we discuss the protective roles of biofilms against current L. pneumophila sanitation strategies along with the initial data available on the regulation of L. pneumophila biofilm formation.

First report of a Chinese PFOS alternative overlooked for 30 years: its toxicity, persistence, and presence in the environment

This is the first report on the environmental occurrence of a chlorinated polyfluorinated ether sulfonate (locally called F-53B, C8ClF16O4SK). It has been widely applied as a mist suppressant by the chrome plating industry in China for decades but has evaded the attention of environmental research and regulation. In this study, F-53B was found in high concentrations (43-78 and 65-112 μg/L for the effluent and influent, respectively) in wastewater from the chrome plating industry in the city of Wenzhou, China. F-53B was not successfully removed by the wastewater treatments in place. Consequently, it was detected in surface water that receives the treated wastewater at similar levels to PFOS (ca. 10-50 ng/L) and the concentration decreased with the increasing distance from the wastewater discharge point along the river. Initial data presented here suggest that F-53B is moderately toxic (Zebrafish LC50-96 h 15.5 mg/L) and is as resistant to degradation as PFOS. While current usage is limited to the chrome plating industry, the increasing demand for PFOS alternatives in other sectors may result in expanded usage. Collectively, the results of this work call for future assessments on the effects of this overlooked contaminant and its presence and fate in the environment.

Stationary phase and mature infectious forms of Legionella pneumophila produce distinct viable but non-culturable cells

Legionella pneumophila is an intracellular bacterial parasite of freshwater protozoa and an accidental waterborne human pathogen. L. pneumophila is highly pleomorphic showing several forms that differentiate within its developmental cycle. In water, L. pneumophila produces viable but non-culturable cells (VBNCCs), which remain largely uncharacterized. We produced VBNCCs from two developmental forms of L. pneumophila [stationary phase forms (SPFs) and mature infectious forms (MIFs)] in two water microcosms [double-deionized (dd) and tap water] at 45°C. In contrast with SPFs, MIFs upheld a robust ultrastructure and high viability in the two water microcosms. In dd-water, MIFs and SPFs lost their culturability faster than in tap water and did not consume their poly-β-hydroxybutyrate inclusions. Resuscitation in Acanthamoeba castellani was only possible for VBNCCs produced from SPFs in tap water. Addition of salts to dd-water prolonged L. pneumophila culturability to tap water levels, suggesting that L. pneumophila requires ions to maintain its readiness to resume growth. VBNCCs resisted detergent lysis and digestion in the ciliate Tetrahymena, except for VBNCCs produced from SPFs in dd-water. L. pneumophila VBNCCs thus show distinct traits according to its originating developmental form and the surrounding water microcosm.

Preferential colonization and release of Legionella pneumophila from mature drinking water biofilms grown on copper versus unplasticized polyvinylchloride coupons

Legionella occurrence in premise drinking water (DW) systems contributes to legionellosis outbreaks, especially in the presence of suitable protozoan hosts. This study examined L. pneumophila behavior within DW biofilms grown on copper (Cu) and unplasticized polyvinylchloride (uPVC) surfaces in the presence of Acanthamoeba polyphaga. One year-old DW biofilms were established within six CDC biofilm reactors: three each containing Cu or uPVC coupons. Biofilms were then inoculated with L. pneumophila (uPVC-Lp and Cu-Lp), or L. pneumophila and A. polyphaga (uPVC-Lp/Ap and Cu-Lp/Ap) and compared to sterile water inoculated controls (uPVC- and Cu-Control) over a 4 month period. L. pneumophila appeared more persistent by qPCR within Cu biofilms in the presence of A. polyphaga compared to uPVC biofilms with or without A. polyphaga, but maintained their cultivability in uPVC biofilms compared to Cu biofilms. Also, persistent shedding of L. pneumophila cells (assayed by qPCR) in the effluent water implied colonization of L. pneumophila within Cu-coupon reactors compared to no detection from uPVC-coupon reactor effluent 14 days after inoculation. Hence, L. pneumophila appeared to colonize Cu surfaces more effectively and may be shed from the biofilms at a greater frequency and duration compared to L. pneumophila colonized uPVC surfaces with host amoebae playing a role in L. pneumophila persistence within Cu biofilms.

Interaction of Legionella pneumophila and Helicobacter pylori with bacterial species isolated from drinking water biofilms

BACKGROUND

It is well established that Legionella pneumophila is a waterborne pathogen; by contrast, the mode of Helicobacter pylori transmission remains unknown but water seems to play an important role. This work aims to study the influence of five microorganisms isolated from drinking water biofilms on the survival and integration of both of these pathogens into biofilms.

RESULTS

Firstly, both pathogens were studied for auto- and co-aggregation with the species isolated from drinking water; subsequently the formation of mono and dual-species biofilms by L. pneumophila or H. pylori with the same microorganisms was investigated. Neither auto- nor co-aggregation was observed between the microorganisms tested. For biofilm studies, sessile cells were quantified in terms of total cells by SYTO 9 staining, viable L. pneumophila or H. pylori cells were quantified using 16 S rRNA-specific peptide nucleic acid (PNA) probes and cultivable cells by standard culture techniques. Acidovorax sp. and Sphingomonas sp. appeared to have an antagonistic effect on L. pneumophila cultivability but not on the viability (as assessed by rRNA content using the PNA probe), possibly leading to the formation of viable but noncultivable (VBNC) cells, whereas Mycobacterium chelonae increased the cultivability of this pathogen. The results obtained for H. pylori showed that M. chelonae and Sphingomonas sp. help this pathogen to maintain cultivability for at least 24 hours.

CONCLUSIONS

It appears that M. chelonae may have an important role in the survival of both pathogens in drinking water. This work also suggests that the presence of some microorganisms can decrease the cultivability of L. pneumophila but not the viability which indicates that the presence of autochthonous microorganisms can lead to misleading results when the safety of water is assessed by cultivable methods alone.

Influence of Plumbing Materials on Biofilm Formation and Growth of Legionella pneumophila in Potable Water Systems

A two-stage chemostat model of a plumbing system was developed, with tap water as the sole nutrient source. The model system was populated with a naturally occurring inoculum derived from an outbreak of Legionnaires' disease and containing Legionella pneumophila along with associated bacteria and protozoa. The model system was used to develop biofilms on the surfaces of a range of eight plumbing materials under controlled, reproducible conditions. The materials varied in their abilities to support biofilm development and the growth of L. pneumophila. Elastomeric surfaces had the most abundant biofilms supporting the highest numbers of L. pneumophila CFU; this was attributed to the leaching of nutrients for bacterial growth from the materials. No direct relationship existed between total biofouling and the numbers of L. pneumophila CFU.

Legionella, protozoa, and biofilms: interactions within complex microbial systems

Currently, the investigation of Legionella ecology falls into two distinct areas of research activity: (1) that Legionella multiply within water sources by parasitizing amoebic or ciliate hosts or (2) that Legionella grows extracellularly within biofilms. Less focus has been given to the overlaps that may occur between these two areas or the likelihood that Legionella employs multiple survival strategies to persist in water sources. It is likely that Legionella interacts with protozoa, bacteria, algae, fungi, etc., and biofilm components in a more complex fashion than multiplication or death due to the presence or absence of single components of these complex microbial systems. This paper addresses gaps that exist in the understanding of Legionella ecology and serves to pinpoint areas of future research. To assume that only one other class of organism is important to Legionella ecology may limit our understanding of how this bacterium proliferates in heated water sources and also limit our strategies for its control in the built environment.

Biofilms: the environmental playground of Legionella pneumophila

Legionella pneumophila, the aetiological agent of 90% of legionellosis cases, is a common inhabitant of natural and anthropogenic freshwater environments, where it resides in biofilms. Biofilms are defined as complex, natural assemblages of microorganisms that involve a multitude of trophic interactions. A thorough knowledge and understanding of Legionella ecology in relation to biofilm communities is of primary importance in the search for innovative and effective control strategies to prevent the occurrence of disease cases. This review provides a critical update on the state-of-the-art progress in understanding the mechanisms and factors affecting the biofilm life cycle of L. pneumophila. Particular emphasis is given to discussing the different strategies this human pathogen uses to grow and retain itself in biofilm communities. Biofilms develop not only at solid-water interfaces (substrate-associated biofilms), but also at the water-air interface (floating biofilms). Disturbance of the water surface can lead to liberation of aerosols derived from the floating biofilm into the atmosphere that allow transmission of biofilm-associated pathogens over considerable distances. Recent data concerning the occurrence and replication of L. pneumophila in floating biofilms are also elaborated and discussed.

Replication of Legionella pneumophila in biofilms of water distribution pipes

Biofilms similar to those present in water distribution pipes of anthropogenic aquatic systems were simulated in a rotating annular reactor using a non-Legionella community consisting of Aeromonas hydrophila, Escherichia coli, Flavobacterium breve and Pseudomonas aeruginosa. The impact of this community and Acanthamoeba castellanii on the replication of Legionella pneumophila was investigated. Despite the presence of 10(7) non-Legionella bacteria, culture and real-time polymerase chain reaction (PCR) results clearly showed that biofilm-associated Legionella bacteria only increased after intracellular replication in A. castellanii. Fluorescent in situ hybridization (FISH) staining of biofilm samples revealed that 48 h after addition of amoebae to the reactor, the amoeba population was lysing and replicated Legionella bacteria were released into the bulk water. This study demonstrated that amoebae like A. castellanii can play a crucial role in the increase and spread of L. pneumophila in anthropogenic aquatic systems and thus in the occurrence of Legionnaires' disease.

Impact of non-Legionella bacteria on the uptake and intracellular replication of Legionella pneumophila in Acanthamoeba castellanii and Naegleria lovaniensis

In aquatic environments, Legionella pneumophila survives, in association with other bacteria, within biofilms by multiplying in free-living amoebae. The precise mechanisms underlying several aspects of the uptake and intracellular replication of L. pneumophila in amoebae, especially in the presence of other bacteria, remain unknown. In the present study, we examined the competitive effect of selected non-Legionella bacteria (Escherichia coli, Aeromonas hydrophila, Flavobacterium breve, and Pseudomonas aeruginosa) on the uptake of L. pneumophila serogroup 1 by the amoebae Acanthamoeba castellanii and Naegleria lovaniensis. We also investigated their possible influence on the intracellular replication of L. pneumophila in both amoeba species. Our results showed that the non-Legionella bacteria did not compete with L. pneumophila for uptake, suggesting that the amoeba hosts took in L. pneumophila through a specific and presumably highly efficient uptake mechanism. Living and heat-inactivated P. aeruginosa best supported the replication of L. pneumophila in N. lovaniensis and A. castellanii, respectively, whereas for both amoeba species, E. coli yielded the lowest number of replicated L. pneumophila. Furthermore, microscopic examination showed that 100% of the A. castellanii and only 2% of the N. lovaniensis population were infected with L. pneumophila at the end of the experiment. This study clearly shows the influence of some non-Legionella bacteria on the intracellular replication of L. pneumophila in A. castellanii and N. lovaniensis. It also demonstrates the different abilities of the two tested amoeba species to serve as a proper host for the replication and distribution of the human pathogen in man-made aquatic environments such as cooling towers, shower heads, and air conditioning systems with potential serious consequences for human health.

Bacterial biofilms: an emerging link to disease pathogenesis

The role of biofilms in the pathogenesis of some chronic human infections is now widely accepted. However, the criteria used to determine whether a given infection is caused by biofilms remain unclear. In this chapter we discuss three infections that are caused by biofilms--infectious kidney stones, bacterial endocarditis, and cystic fibrosis lung infections--and focus on the role of the biofilm in disease pathogenesis. Biofilms are also important as environmental reservoirs for pathogens, and the biofilm growth mode may provide organisms with survival advantages in natural environments and increase their virulence. The consequences of pathogens living in environmental biofilms and an analysis of some specific environmental biofilm systems are presented.

Microbiological safety of drinking water

Emerging pathogens in drinking water have become increasingly important during the decade. These include newly-recognized pathogens from fecal sources such as Cryptosporidium parvum, Campylobacter spp., and rotavirus, as well as pathogens that are able to grow in water distribution systems, like Legionella spp., mycobacteria, and aeromonads. To perform a risk analysis for the pathogens in drinking water, it is necessary to understand the ecology of these organisms. The ecology of the drinking-water distribution system has to be evaluated in detail, especially the diversity and physiological properties of water bacteria. The interactions between water bacteria and (potential) pathogens in such diverse habitats as free water and biofilms are essential for the survival or growth of hygienically relevant organisms in drinking water. Results of epidemiological studies together with ecological data are the basis for effective resource protection, water treatment, and risk assessment.

A paint incorporating silver to control mixed biofilms containing Legionella pneumophila

A three-stage chemostat containing a mixed consortium of microorganisms, including Legionella pneumophila, was used to determine the suitability of a silver-containing paint to control biofouling in water systems. The paint was efficient in controlling total surface colonisation by heterotrophic microorganisms and growth of the pathogen over a 2-week period. Biodiversity was limited in the presence of the silver paint and this was thought to help control L. pneumophila numbers. Glass control tiles suspended alongside the silver painted tiles also had reduced colonisation for the 2-week period, suggesting that low levels of silver leached from the paint surface. This loss of silver was confirmed since the inhibition of biofouling and inclusion of the pathogen was not maintained after the 2-week period. Although this paint was unsuitable for controlling biofouling over extended time periods, the data suggest that a reformulated paint or electrochemical method of introducing silver ions may be successful.

Influence of temperature and plumbing material selection on biofilm formation and growth of Legionella pneumophila in a model potable water system containing complex microbial flora

Survival and growth of Legionella pneumophila in both biofilm and planktonic phases were determined with a two-stage model system. The model used filter-sterilized tap water as the sole source of nutrient to culture a naturally occurring mixed population of microorganisms including virulent L. pneumophila. At 20 degrees C, L. pneumophila accounted for a low proportion of biofilm flora on polybutylene and chlorinated polyvinyl chloride, but was absent from copper surfaces. The pathogen was most abundant on biofilms on plastics at 40 degrees C, where it accounted for up to 50% of the total biofilm flora. Copper surfaces were inhibitory to total biofouling and included only low numbers of L. pneumophila organisms. The pathogen was able to survive in biofilms on the surface of the plastic materials at 50 degrees C, but was absent from the copper surfaces at the same temperature. L. pneumophila could not be detected in the model system at 60 degrees C. In the presence of copper surfaces, biofilms forming on adjacent control glass surfaces were found to incorporate copper ions which subsequently inhibited colonization of their surfaces. This work suggests that the use of copper tubing in water systems may help to limit the colonization of water systems by L. pneumophila.

Impact of growth conditions on resistance of Klebsiella pneumoniae to chloramines

The resistance of Klebsiella pneumoniae to inorganic monochloramine (1.5 mg/liter; 3:1 Cl2:N ratio, pH 8.0) was examined in relation to growth phase, temperature of growth, and growth under decreased nutrient conditions. Growth phase did not impact resistance to chloramines. Mid-exponential and stationary-phase cells, grown in a yeast extract-based medium, had CT99 values and standard deviations of 4.8 +/- 0.1 and 4.6 +/- 0.2 mg.min/liter, respectively. Growth temperature did not alter chloramine resistance at short contact times. CT99 values of cells grown at 15 and 23 degrees C were 4.5 +/- 0.2 and 4.6 +/- 0.2 mg.min/liter, respectively. However, at longer contact times, CT99.99 values of cells grown at 15 and 23 degrees C were 14 and 8 mg.min/liter, respectively, suggesting a small resistant subpopulation for cells grown at the lower temperature. Growth under decreased nutrient conditions resulted in a concomitant increase in resistance to chloramines. When K. pneumoniae was grown in undiluted Ristroph medium and Ristroph medium diluted by 1:100 and 1:1,000, the CT99 values were 4.6 +/- 0.2, 9.6 +/- 0.4, and 24 +/- 7.0 mg.min/liter, respectively. These results indicate that nutrient availability has a greater impact than growth phase or growth temperature in promoting the resistance of K. pneumoniae to inorganic monochloramine.

Immunogold and fluorescein immunolabelling of Legionella pneumophila within an aquatic biofilm visualized by using episcopic differential interference contrast microscopy

Biofilms containing diverse microflora were developed in tap water on glass and polybutylene surfaces. Legionella pneumophila within the biofilms was labelled with monoclonal antibodies and visualized with immunogold or fluorescein isothiocyanate conjugates. Development of a differential interference contrast technique in an episcopic mode enabled simultaneous visualization of the total biofilm flora and gold-labelled legionellae. The legionellae occurred in microcolonies within the biofilm in the absence of amoebae, suggesting that the bacterial consortium was supplying sufficient nutrients to enable legionellae to grow extracellularly within the biofilm.

Distribution of Legionella spp. in hydrothermal areas in continental Portugal and the island of São Miguel, Azores

Nineteen aquatic environment sites from three hydrothermal areas on continental Portugal and one area on the island of São Miguel, Azores, were examined for the recovery of Legionella spp. Physicochemical and bacteriological parameters were also determined for each site. Water temperatures varied between 22 and 67.5 degrees C, although the majority had temperatures above 40 degrees C; the pH varied between 5.5 and 9.2. The number of Legionella spp. recovered varied between 5.0 x 10(2) and 2.3 x 10(6) CFU/liter. A total of 288 isolates from 14 sites were identified by indirect immunofluorescence assay. The majority of the isolates belonged to Legionella pneumophila (74.3%), of which most belong to serogroup 1, but the relative proportion of L. pneumophila serogroups varied considerably. L. pneumophila serogroup 1 constituted 96.2% of the isolates in area 2 from central Portugal, but no isolates of this serogroup were recovered from São Miguel, where serogroup 6 strains were the predominant isolates. Ninety-six percent of the L. pneumophila serogroup 1 isolates belonged to monoclonal antibody subgroups OLDA and Bellingham. Other species identified were L. bozemanii serogroup 2, L. dumoffii, L. micdadei, L. moravica, L. oakridgensis, L. sainticrucis, and L. sainthelensi. Two undescribed species, which react by indirect immunofluorescence assay to antisera to "L. londoniensis" and "L. nautarum" and a group of isolates with strong cross-reaction to L. cincinnatiensis/L. sainticrucis/L. longbeachae by indirect immunofluorescence assay were also recovered. The latter were the only isolates recovered from area 3, in east central Portugal, over a period of 1 year.

The incidence of Bdellovibrio spp. in man-made water systems: coexistence with legionellas

Bdellovibrios have been isolated from surface waters but there are no reports of its occurrence in mains water supplies. One hundred and thirty five water samples from 81 sources were examined for the presence of Bdellovibrio bacteriovorus and Legionella spp. Bdellovibrios were isolated by a double-layer agar technique with two strains of Legionella pneumophila serogroup 1 as the host organisms. Bdellovibrio spp. were isolated from 57.8% and Legionella spp. from 9.5% of the samples. The two species occurred together in 4.4% of samples. The incidence of Bdellovibrio spp. and its occurrence with legionellas in man-made water systems is discussed.

Growth-supporting activity for Legionella pneumophila in tap water cultures and implication of hartmannellid amoebae as growth factors

Photosynthetic cyanobacteria, heterotrophic bacteria, free-living amoebae, and ciliated protozoa may support growth of Legionella pneumophila. Studies were done with two tap water cultures (WS1 and WS2) containing L. pneumophila and associated microbiota to characterize growth-supporting activity and assess the relative importance of the microbiota in supporting multiplication of L. pneumophila. The water cultures were incubated in the dark at 35 degrees C. The growth-supporting factor(s) was separated from each culture by filtration through 1-micron-pore-size membrane filters. The retentate was then suspended in sterile tap water. Multiplication of L. pneumophila occurred when both the retentate suspension and the filtrate from either culture were inoculated into sterile tap water. L. pneumophila did not multiply in tap water inoculated with only the filtrate, even though filtration did not reduce the concentration of L. pneumophila or heterotrophic bacteria in either culture. Growth-supporting activity of the retentate suspension from WS1 was inactivated at 60 degrees C but unaffected at 0, 25, and 45 degrees C after 30-min incubations. Filtration experiments indicated that the growth-supporting factor(s) in WS1 was 2 to 5 micron in diameter. Ciliated protozoa were not detected in either culture. Hartmannellid amoebae were conclusively demonstrated in WS2 but not in WS1. L. pneumophila multiplied in tap water inoculated with the amoebae (10(3)/ml) and the 1-micron filtrate of WS2. No multiplication occurred in tap water inoculated with the filtrate only. Growth-supporting activity for L. pneumophila may be present in plumbing systems; hartmannellid amoebae appear to be important determinants of multiplication of L. pneumophila in some tap water cultures.

Effects of FLONLIZER, ultraviolet sterilizer, on Legionella species inhabiting cooling tower water

Legionella pneumophila in sterile distilled water was not detected after ultraviolet irradiation by FLONLIZER, a new-type sterilizer, at a flow rate of 82.5 to 364.8 liters/hr. When irradiated by FLONLIZER at a flow rate of under 324.0 liters/hr, no viable cells of legionellae, other heterotrophic bacteria and bacterivorous protozoa were detected in the cooling tower water, which was found to contain L. pneumophila. No viable cells of L. pneumophila and L. bozemanii suspended in sterile distilled water were detected after the irradiation with UV-doses of over 6.16 X 10(3) micro W.sec/cm2. At the irradiation of low UV-doses under 1.06 X 10(4) micro W.sec/cm2, the viable count of legionellae recuperated by photoreactivation from UV-damage increased with the exposure time under a white fluorescent lamp. However, in the samples irradiated with UV-doses of over 3.52 X 10(4) micro W.sec/cm2, equal to the FLONLIZER, legionellae did not recuperate even after 18 hr illumination with a white fluorescent lamp. FLONLIZER is thus expected to act as a sterilizer which can control the legionellae inhabiting cooling tower systems placed in outdoor space.

Survival and multiplication of Legionella pneumophila in municipal drinking water systems

Studies were conducted to investigate the survival and multiplication of Legionella spp. in public drinking water supplies. An attempt was made, over a period of several years, to isolate legionellae from a municipal system. Sampling sites included the river water supply, treatment plant, finished water reservoir system, mains, and distribution taps. Despite the use of several isolation techniques, Legionella spp. could not be detected in any of the samples other than those collected from the river. It was hypothesized that this was due to the maintenance of a chlorine residual throughout the system. To investigate the potential for Legionella growth, additional water samples, collected from throughout the system, were dechlorinated, pasteurized, and inoculated with Legionella pneumophila. Subsequent growth indicated that many of these samples, especially those collected from areas affected by an accumulation of algal materials, exhibited a much greater ability to support Legionella multiplication than did river water prior to treatment. Chemical analyses were also performed on these samples. Correlation of chemical data and experimental growth results indicated that the chemical environment significantly affects the ability of the water to support multiplication, with turbidity, organic carbon, and certain metals being of particular importance. These studies indicate that the potential exists for Legionella growth within municipal systems and support the hypothesis that public water supplies may contaminate the plumbing systems of hospitals and other large buildings. The results also suggest that useful methods to control this contamination include adequate treatment plant filtration, maintenance of a chlorine residual throughout the treatment and distribution network, and effective covering of open reservoirs.

Effects of metals on Legionella pneumophila growth in drinking water plumbing systems

An investigation of the chemical environment and growth of Legionella pneumophila in plumbing systems was conducted to gain a better understanding of its ecology in this habitat. Water samples were collected from hospital and institutional hot-water tanks known to have supported L. pneumophila and were analyzed for 23 chemical parameters. The chemical environment of these tanks was found to vary extensively, with the concentrations of certain metals reaching relatively high levels due to corrosion. The effect of various chemical conditions on L. pneumophila growth was then examined by observing its multiplication in the chemically analyzed hot-water tank samples after sterilization and reinoculation with L. pneumophila. L. pneumophila and associated microbiota used in these experiments were obtained from a hot-water tank. These stains were maintained in tap water and had never been passaged on agar. The results of the growth studies indicate that although elevated concentrations of a number of metals are toxic, lower levels of certain metals such as iron, zinc, and potassium enhance growth of naturally occurring L. pneumophila. Parallel observations on accompanying non-Legionellaceae bacteria failed to show the same relationship. These findings suggest that metal plumbing components and associated corrosion products are important factors in the survival and growth of L. pneumophila in plumbing systems and may also be important in related habitats such as cooling towers and air-conditioning systems.