Detection of cyanotoxins, β-N-methylamino-L-alanine and microcystins, from a lake surrounded by cases of amyotrophic lateral sclerosis

A cluster of amyotrophic lateral sclerosis (ALS) has been previously described to border Lake Mascoma in Enfield, NH, with an incidence of ALS approximating 25 times expected. We hypothesize a possible association with cyanobacterial blooms that can produce β-N-methylamino-L-alanine (BMAA), a neurotoxic amino acid implicated as a possible cause of ALS/PDC in Guam. Muscle, liver, and brain tissue samples from a Lake Mascoma carp, as well as filtered aerosol samples, were analyzed for microcystins (MC), free and protein-bound BMAA, and the BMAA isomers 2,4-diaminobutyric acid (DAB) and N-(2-aminoethyl)glycine (AEG). In carp brain, BMAA and DAB concentrations were 0.043 μg/g ± 0.02 SD and 0.01 μg/g ± 0.002 SD respectively. In carp liver and muscle, the BMAA concentrations were 1.28 μg/g and 1.27 μg/g respectively, and DAB was not detected. BMAA was detected in the air filters, as were the isomers DAB and AEG. These results demonstrate that a putative cause for ALS, BMAA, exists in an environment that has a documented cluster of ALS. Although cause and effect have not been demonstrated, our observations and measurements strengthen the association.

A large community outbreak of Legionnaires’ disease in Vila Franca de Xira, Portugal, October to November 2014

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A large community outbreak of Legionnaires disease in Vila Franca de Xira, Portugal, October to November 2014

An outbreak of Legionnaires’ disease with 334 confirmed cases was identified on 7 November 2014 in Vila Franca de Xira, Portugal and declared controlled by 21 November. Epidemiological, environmental and microbiological analysis identified industrial wet cooling systems to be the probable source of infection. Preliminary results from sequence-based typing of clinical specimens and environmental isolates confirmed this link. A series of meteorological phenomena are likely to have contributed to the scale of this outbreak.

An unusually long-lasting outbreak of community-acquired Legionnaires' disease, 2005–2008, Italy

An unusually long-lasting community-acquired outbreak of Legionnaires’ disease (LD) occurred in the inhabitants of a town in northern Italy from 2005 to 2008. Overall, 43 cases were diagnosed including five deaths. Hundreds of water samples were collected forLegionellaisolation but only two clinical samples were obtained. Clinical strains were ST23 as were environmental isolates detected in mostLegionella-positive patients' homes and those from a public fountain. Although noLegionellawas found in the municipal water mains, a continuous chlorination was applied in 2008. This action resulted in a halving of cases, although incidence remained tenfold higher than the Italian average incidence until the end of 2013, when it dropped to the expected rate. Retrospective analyses of prevalent wind direction suggested that a hidden cooling tower could have been the main cause of this uncommon outbreak, highlighting the importance of implementation of cooling tower registers in supporting LD investigations.

Strategies for controlling non-transmissible infection outbreaks using a large human movement data set

Prediction and control of the spread of infectious disease in human populations benefits greatly from our growing capacity to quantify human movement behavior. Here we develop a mathematical model for non-transmissible infections contracted from a localized environmental source, informed by a detailed description of movement patterns of the population of Great Britain. The model is applied to outbreaks of Legionnaires' disease, a potentially life-threatening form of pneumonia caused by the bacteria Legionella pneumophilia. We use case-report data from three recent outbreaks that have occurred in Great Britain where the source has already been identified by public health agencies. We first demonstrate that the amount of individual-level heterogeneity incorporated in the movement data greatly influences our ability to predict the source location. The most accurate predictions were obtained using reported travel histories to describe movements of infected individuals, but using detailed simulation models to estimate movement patterns offers an effective fast alternative. Secondly, once the source is identified, we show that our model can be used to accurately determine the population likely to have been exposed to the pathogen, and hence predict the residential locations of infected individuals. The results give rise to an effective control strategy that can be implemented rapidly in response to an outbreak.

Public health strategies for infectious disease control can benefit greatly from our growing capacity to predict human movement behaviour. This is facilitated by modern methods of electronic data generation and storage that allow us to track detailed human movement patterns. Here we develop a mathematical model of the dynamics of non-transmissible infections that is informed by a new data set describing detailed movements of the population of Great Britain. We apply the model to three outbreaks of Legionnaires' disease. We demonstrate how the method can assist during the crucial early stages of an outbreak by providing predictions of the infection source location and individuals with a high exposure risk.

Barrow-in-Furness: a large community legionellosis outbreak in the UK

A community outbreak of legionellosis occurred in Barrow-in-Furness, Cumbria, during July and August 2002. A descriptive study and active case-finding were instigated and all known wet cooling systems and other potential sources were investigated. Genotypic and phenotypic analysis, and amplified fragment length polymorphism of clinical human and environmental isolates confirmed the air-conditioning unit of a council-owned arts and leisure centre to be the source of infection. Subsequent sequence-based typing confirmed this link. One hundred and seventy-nine cases, including seven deaths [case fatality rate (CFR) 3·9%] were attributed to the outbreak. Timely recognition and management of the incident very likely led to the low CFR compared to other outbreaks. The outbreak highlights the responsibility associated with managing an aerosol-producing system, with the potential to expose and infect a large proportion of the local population and the consequent legal ramifications and human cost.

Potential role of bacteria packaging by protozoa in the persistence and transmission of pathogenic bacteria

Many pathogenic bacteria live in close association with protozoa. These unicellular eukaryotic microorganisms are ubiquitous in various environments. A number of protozoa such as amoebae and ciliates ingest pathogenic bacteria, package them usually in membrane structures, and then release them into the environment. Packaged bacteria are more resistant to various stresses and are more apt to survive than free bacteria. New evidence indicates that protozoa and not bacteria control the packaging process. It is possible that packaging is more common than suspected and may play a major role in the persistence and transmission of pathogenic bacteria. To confirm the role of packaging in the propagation of infections, it is vital that the molecular mechanisms governing the packaging of bacteria by protozoa be identified as well as elements related to the ecology of this process in order to determine whether packaging acts as a Trojan Horse.

Free-living amoebae (FLA) co-occurring with legionellae in industrial waters

Legionella pneumophila is known as the causative agent of Legionnaires’ disease and free-living amoebae (FLA) can serve as vehicles for legionellae. The aim of this study was to screen industrial waters for the occurrence of FLA and their co-occurrence with legionellae. A total of 201 water samples, including 129 cooling waters and 72 process waters, and 30 cooling lubricants were included in the study. Treated waters were screened periodically, pre and post treatment. Altogether, 72.6% of the water samples were positive for FLA, acanthamoebae being most prevalent (in 23.9% of the samples) followed by Vermamoeba vermiformis (19.4%). Only one cooling lubricant was positive (Acanthamoeba genotype T4). Legionella spp. were detected in 34.8% of the water samples and in 15% in high concentrations (>1000 CFU/100 ml). Altogether, 81.4% of the Legionella-positive samples were positive for FLA by standard methods. By applying a highly sensitive nested PCR to a representative set of random samples it was revealed that Legionella spp. always co-occurred with Acanthamoeba spp. Although the addition of disinfectants did influence amoebal density and diversity, treated waters showed no difference concerning FLA in the interphases of disinfection. It appears that FLA can re-colonize treated waters within a short period of time.

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.

Legionella pneumonia cases over a five-year period: a descriptive, retrospective study of outcomes in a UK district hospital

As the recent outbreaks in Edinburgh and Camarthen, UK, have shown, Legionella pneumonia (LP) remains a significant public health problem, which is not only confined to those who have travelled abroad. In both outbreaks and sporadic cases, diagnosis can go unrecognised. We reviewed the demographics, comorbidities, diagnosis, treatment and clinical outcome of LP cases over five years in a district general hospital in northwest England. Over half of LP cases were UK acquired and 'classic' clinical features were common. Clinical criteria for diagnosing LP were confirmed, but few sputum samples were sent to reference laboratories, limiting further essential epidemiological mapping of UK cases. Following current UK community-acquired pneumonia guidance would have missed nearly one quarter of LP cases in our series, potentially leading to further morbidity and mortality.

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.

Investigation of outbreaks: epidemiology

Outbreaks of Legionnaires' disease create high levels of public anxiety and media interest and inevitably consume a great deal of public health resources. Investigations should begin as early as possible in order to rapidly identify suspected sources of infection, control the outbreak and prevent further cases occurring. The investigations should be coordinated by an outbreak control team who work collaboratively within local/national/international public health guidelines and with clear terms of reference. The actions carried out by epidemiologists when investigating community-, hospital-, or travel-associated outbreaks are comprehensively outlined in this chapter. The microbiological and environmental actions that complement this work are discussed in the accompanying chapters.

Aerosolization of cyanobacteria as a risk factor for amyotrophic lateral sclerosis

Sporadic amyotrophic lateral sclerosis (sALS) is a fatal neurodegenerative disease with no known cause. There are many clues to suggest an environmental trigger for the disease, including reports of conjugal couples and co-localized employees that developed sALS. On the island of Guam,a very high incidence of sALS occurred among the Chamorro natives back in the 1940s and 1950s and has been linked to the neurotoxin beta-N-methylamino-L-alanine (BMAA) that is produced by cyanobacteria that live symbiotically in the roots of the cycad plant, the seeds from which were a staple of the Chamorro diet. It has been shown that BMAA was biomagnified up the food chain from the cycad seeds to the now largely extinct, indigenous flying foxes, a former delicacy of the Chamorro natives. Recent evidence suggests that long term, chronic exposure to low levels of BMAA might cause ALS in genetically predisposed individuals. Many exposure routes to BMAA have been implicated thus far, including consumption of contaminated food and exposure to water harboring cyanobacterial blooms which have the capability of producing BMAA. Aerosolization is a well documented means for bacterial or toxin exposure causing subsequent illness, as in the case of brevetoxins and pulmonary disease and Legionnaire's disease. We hypothesize that some cases of ALS may be related to chronic exposure to the aerosolization of cyanobacteria derived BMAA from cooling towers and might explain the observation of conjugal ALS couples.

Legionnaires' disease from a cooling tower in a community outbreak in Lidköping, Sweden- epidemiological, environmental and microbiological investigation supported by meteorological modelling

Background

An outbreak of Legionnaires’ Disease took place in the Swedish town Lidköping on Lake Vänern in August 2004 and the number of pneumonia cases at the local hospital increased markedly. As soon as the first patients were diagnosed, health care providers were informed and an outbreak investigation was launched.

Methods

Classical epidemiological investigation, diagnostic tests, environmental analyses, epidemiological typing and meteorological methods.

Results

Thirty-two cases were found. The median age was 62 years (range 36 – 88) and 22 (69%) were males. No common indoor exposure was found. Legionella pneumophila serogroup 1 was found at two industries, each with two cooling towers. In one cooling tower exceptionally high concentrations, 1.2 × 10⁹ cfu/L, were found. Smaller amounts were also found in the other tower of the first industry and in one tower of the second plant. Sero- and genotyping of isolated L. pneumophila serogroup 1 from three patients and epidemiologically suspected environmental strains supported the cooling tower with the high concentration as the source. In all, two L. pneumophila strains were isolated from three culture confirmed cases and both these strains were detected in the cooling tower, but one strain in another cooling tower as well. Meteorological modelling demonstrated probable spread from the most suspected cooling tower towards the town centre and the precise location of four cases that were stray visitors to Lidköping.

Conclusions

Classical epidemiological, environmental and microbiological investigation of an LD outbreak can be supported by meteorological modelling methods.

The broad competence and cooperation capabilities in the investigation team from different authorities were of paramount importance in stopping this outbreak.

Molecular characterization of clinical and environmental isolates of Legionella pneumophila in Norway, 2001-2008

BACKGROUND

The aims of the study were to determine the molecular characteristics of a collection of Legionella pneumophila isolates from 45 cases with Legionnaires' disease and from 96 environmental samples, received by the national reference laboratory in Norway between 2001 and 2008, to use these characteristics to identify links between cases and suspected sources of infection, and to compare the isolate characteristics with those in other European countries.

METHODS

The isolates were characterized by 7-gene locus sequence-based typing and dot-blotting with monoclonal antibodies to various serogroups and subgroups.

RESULTS

The clinical isolates represented 12.6% of the 357 cases notified in Norway between 2001 and 2008, during which 3 outbreaks of L. pneumophila serogroup 1 occurred. Outbreak cases constituted 62.2% of the cases, followed by travel-associated (24.4%) and sporadic cases (11.1%). Forty-two (93.3%) of the clinical and 69 (71.9%) of the environmental isolates were serogroup 1, and 39 (86.7%) and 50 (52.1%) isolates, respectively, carried the monoclonal antibody (Mab) 3/1 virulence-associated epitope. The clinical isolates belonged to 17 sequence types and the environmental isolates to 19 sequence types. neuA was not detected in 23 environmental isolates.

CONCLUSIONS

Matching characteristics of sequence types and monoclonal subgroups for case and environmental isolates were obtained for all 3 outbreaks and for 2 of 5 cases of sporadic disease. Sampling during the outbreaks accounted for the higher proportion of serogroup 1 and Mab 3/1-positive environmental isolates in comparison with other European strain collections.

Legionellae in engineered systems and use of quantitative microbial risk assessment to predict exposure

While it is well-established that Legionella are able to colonize engineered water systems, the number of interacting factors contributing to their occurrence, proliferation, and persistence are unclear. This review summarizes current methods used to detect and quantify legionellae as well as the current knowledge of engineered water system characteristics that both favour and promote legionellae growth. Furthermore, the use of quantitative microbial risk assessment (QMRA) models to predict potentially critical human exposures to legionellae are also discussed. Understanding the conditions favouring Legionella occurrence in engineered systems and their overall ecology (growth in these systems/biofilms, biotic interactions and release) will aid in developing new treatment technologies and/or systems that minimize or eliminate human exposure to potentially pathogenic legionellae.

Epidemiology and control of legionellosis, singapore

To determine trends and clinical and epidemiologic features of legionellosis in Singapore, we studied cases reported during 2000-2009. During this period, 238 indigenous and 33 imported cases of legionellosis were reported. Cases were reported individually and sporadically throughout each year. Although the annual incidence of indigenous cases had decreased from 0.46 cases per 100,000 population in 2003 to 0.16 cases per 100,000 in 2009, the proportion of imported cases increased correspondingly from 6.2% during 2000-2004 to 27.3% during 2005-2009 (p<0.0005). The prevalence of Legionella bacteria in cooling towers and water fountains was stable (range 12.1%-15.3%) during 2004-August 2008.

Molecular evolution of Legionella pneumophila dotA gene, the contribution of natural environmental strains

Given the role of DotA protein in establishing successful infections and the diversity of host cells interacting with Legionella pneumophila in nature, it is possible that this gene product is a target for adaptive evolution. We investigated the influence of L. pneumophila isolates from natural environments with the molecular evolution of this crucial virulence-related gene. The population genetic structure of L. pneumophila was inferred from the partial sequences of rpoB and dotA of 303 worldwide strains. The topology of the two inferred trees was not congruent and in the inferred dotA tree the vast majority of the natural environmental isolates were clustered in a discrete group. The Ka/Ks ratio demonstrated that this group, contrary to all others, has been under strong diversifying selection. The alignment of all DotA sequences allowed the identification of several alleles and the amino acid variations were not randomly distributed. Moreover, from these results we can conclude that dotA from L. pneumophila clinical and man-made environmental strains belong to a sub-set of all genotypes existing in nature. A split graph analysis showed evidence of a network-like organization and several intergenic recombination events were detected within L. pneumophila strains resulting in mosaic genes in which different gene segments exhibited different evolutionary histories. We have determined that the allelic diversity of dotA is predominantly found in L. pneumophila isolates from natural environments, suggesting that niche-specific selection pressures have been operating on this gene. Indeed, the high level of dotA allelic diversity may reflect fitness variation in the persistence of those strains in distinct environmental niches and/or tropism to various protozoan hosts.

Two Legionnaires' disease cases associated with industrial waste water treatment plants: a case report

BACKGROUND

Finnish and Swedish waste water systems used by the forest industry were found to be exceptionally heavily contaminated with legionellae in 2005.

CASE PRESENTATION

We report two cases of severe pneumonia in employees working at two separate mills in Finland in 2006. Legionella serological and urinary antigen tests were used to diagnose Legionnaires' disease in the symptomatic employees, who had worked at, or close to, waste water treatment plants. Since the findings indicated a Legionella infection, the waste water and home water systems were studied in more detail. The antibody response and Legionella urinary antigen finding of Case A indicated that the infection had been caused by Legionella pneumophila serogroup 1. Case A had been exposed to legionellae while installing a pump into a post-clarification basin at the waste water treatment plant of mill A. Both the water and sludge in the basin contained high concentrations of Legionella pneumophila serogroup 1, in addition to serogroups 3 and 13. Case B was working 200 meters downwind from a waste water treatment plant, which had an active sludge basin and cooling towers. The antibody response indicated that his disease was due to Legionella pneumophila serogroup 2. The cooling tower was the only site at the waste water treatment plant yielding that serogroup, though water in the active sludge basin yielded abundant growth of Legionella pneumophila serogroup 5 and Legionella rubrilucens. Both workers recovered from the disease.

CONCLUSION

These are the first reported cases of Legionnaires' disease in Finland associated with industrial waste water systems.

Alternative routes for dissemination of Legionella pneumophila causing three outbreaks in Norway

Three outbreaks of Legionnaires' disease were reported in the Fredrikstad/Sarpsborg community, Norway, in 2005 and 2008 caused by the L. pneumophila ST15 and ST462 strains determined by sequence based typing. In this retrospective study, we suggest that the aeration ponds, a part of the biological treatment plant at Borregaard Ind. Ltd., are the main amplifiers and primary disseminators of the outbreak L. pneumophila strains. This result is supported by the finding that the ST15 and ST462 strains were not able to survive in air scrubber liquid media more than two days of incubation at the scrubber's operating conditions during the 2005 and 2008 outbreaks. In 2008, >10¹⁰ CFU/L of L. pneumophila ST462 were detected in the aeration ponds. ST15 and ST462 were also detected in the river Glomma in 2005 and 2008, respectively, downstream of the wastewater outlet from the treatment plant (10⁵CFU/L). These findings strongly suggest that the presence of L. pneumophila in the river is due to the release of wastewater from the industrial aeration ponds, demonstrating that the river Glomma may be an additional disseminator of L. pneumophila during the outbreaks. This work emphasizes the need for preventive actions against the release of wastewater containing human pathogens to the environment.

Geographical variation of sporadic Legionnaires' disease analysed in a grid model

The aim was to analyse variation in incidence of sporadic Legionnaires' disease in a geographical information system in three time periods (1990–2005) by the application of a grid model and to assess the model's validity by analysing variation according to grid position. Coordinates of the addresses at time of disease of 606 confirmed cases with Legionnaires' disease were obtained. The incidence was calculated in cells of 10×10 km in 25 different grids superimposed on a map of Denmark. A 95% and 99% threshold was applied to identify cells with excess incidence representing potential clusters. Four cells had excess incidence in all three time periods. The analysis in 25 different grid positions indicated a low risk of overlooking cells with excess incidence in a random grid. The coefficient of variation ranged from 0·08 to 0·11 independent of the threshold. By application of a random grid model we demonstrated that it was possible to detect small areas with excess incidence that were not detected in the present surveillance system.

Potentially pathogenic amoeba-associated microorganisms in cooling towers and their control

Cooling towers provide a favorable environment for the proliferation of microorganisms. Cooling towers generate a biofilm and often aerosolize contaminated water, thereby increasing the risk of microorganism dissemination by human inhalation. This pathogen dissemination was first revealed by the epidemics of Legionnaires’ disease that were directly related to the presence of cooling towers, and since then, the ecology of Legionella pneumophila has been well studied. Each country has specific standards regarding the acceptable amount of microorganisms in cooling tower systems. However, those standards typically only concern L. pneumophila, even though many other microorganisms can also be isolated from cooling towers, including protozoa, bacteria and viruses. Microbiological control of the cooling tower system can be principally achieved by chemical treatments and also by improving the system’s construction. Several new treatments are being studied to improve the efficiency of disinfection. However, as most of these treatments continue to focus solely on L. pneumophila, reports of other types of pathogens continue to increase. Therefore, how their dissemination affects the human populous health should be addressed now.

Seroepidemiological study after a long-distance industrial outbreak of legionnaires' disease

Following a long-distance outbreak of Legionnaires' disease from an industrial air scrubber in Norway in 2005, a seroepidemiological study measuring levels of immunoglobulin G (IgG) and IgM antibodies to Legionella pneumophila was performed with a polyvalent enzyme-linked immunosorbent assay. One year after the outbreak, IgG levels in employees (n = 213) at the industrial plant harboring the scrubber and in blood donors (n = 398) from the outbreak county were low but significantly higher (P < or = 0.002) than those in blood donors (n = 406) from a nonexposed county. No differences in IgM levels among the three groups were found after adjustment for gender and age. Home addresses of the seroresponders in the exposed county clustered to the city of the outbreak, in contrast to the scattering of addresses of the seroresponding donors in the nonexposed county. Factory employees who operated at an open biological treatment plant had significantly higher IgG and IgM levels (P < or = 0.034) than those working >200 m away. Most of the healthy seroresponders among the factory employees worked near this exposure source. Immunoblotting showed that IgG and IgM antibodies in 82.1% of all seroresponders were directed to the lipopolysaccharide of the L. pneumophila serogroup 1 outbreak strain. In conclusion, 1 year after the long-distance industrial outbreak a small increase in IgG levels of the exposed population was observed. The open biological treatment plant within the industrial premises, however, constituted a short-distance exposure source of L. pneumophila for factory employees working nearby.

Surface translocation by Legionella pneumophila: a form of sliding motility that is dependent upon type II protein secretion

Legionella pneumophila exhibits surface translocation when it is grown on a buffered charcoal yeast extract (BCYE) containing 0.5 to 1.0% agar. After 7 to 22 days of incubation, spreading legionellae appear in an amorphous, lobed pattern that is most manifest at 25 to 30 degrees C. All nine L. pneumophila strains examined displayed the phenotype. Surface translocation was also exhibited by some, but not all, other Legionella species examined. L. pneumophila mutants that were lacking flagella and/or type IV pili behaved as the wild type did when plated on low-percentage agar, indicating that the surface translocation is not swarming or twitching motility. A translucent film was visible atop the BCYE agar, advancing ahead of the spreading legionellae. Based on its abilities to disperse water droplets and to promote the spreading of heterologous bacteria, the film appeared to manipulate surface tension and, as such, acted like a surfactant. Indeed, a sample obtained from the film rapidly dispersed when it was spotted onto a plastic surface. L. pneumophila type II secretion (Lsp) mutants, but not their complemented derivatives, were defective for both surface translocation and film production. In contrast, mutants defective for type IV secretion exhibited normal surface translocation. When lsp mutants were spotted onto film produced by the wild type, they were able to spread, suggesting that type II secretion promotes the elaboration of the Legionella surfactant. Together, these data indicate that L. pneumophila exhibits a form of surface translocation that is most akin to "sliding motility" and uniquely dependent upon type II secretion.

Tracking airborne Legionella and Legionella pneumophila at a biological treatment plant

Biological treatment plants are frequently used to degrade organic substances in wastewater from wood refinement processes. Aeration ponds in such plants provide an optimal growth environment for many microorganisms, including Legionella species. To investigate whether legionellae could be dispersed as aerosols from the ponds and transported by the wind, the wetted-wall cyclone SASS 2000(PLUS) and the impactors MAS-100 and STA-204 were used to collect air samples directly above, upwind, and downwind of aeration ponds during a 4-month period. Computational fluid dynamics was used a priori to estimate the aerosol paths and to determine suitable air-sampling locations. Several Legionella species, including Legionella pneumophila, were identified in air samples at the biological treatment plant using microbiological and molecular methods. L. pneumophila was identified up to distances of 200 m downwind from the ponds, but, in general, not upwind nor outside the predicted aerosol paths. The highest concentration level of viable legionellae was identified directly above the aeration ponds (3300 CFU/m3). This level decreased as the distance from the aeration ponds increased. Molecular typing indicated that a single clone of L. pneumophila was dispersed from the ponds during the period of the study. Thus, our study demonstrated that aerosols generated at aeration ponds of biological treatment facilities may contain L. pneumophila, which then can be transported by the wind to the surroundings. The methods used in this study may be generically applied to trace biological aerosols that may pose a challenge to environmental occupational health.