Search

Legionella longbeachae causes most cases of legionellosis in Australia and may be underreported worldwide due to the lack of L. longbeachae-specific diagnostic tests. L. longbeachae displays distinctive differences in intracellular trafficking, caspase 1 activation, and infection in mouse models compared to Legionella pneumophila, yet these two species have indistinguishable clinical presentations in humans. Unlike other legionellae, which inhabit freshwater systems, L. longbeachae is found predominantly in moist soil. In this study, we sequenced and annotated the genome of an L. longbeachae clinical isolate from Oregon, isolate D-4968, and compared it to the previously published genomes of L. pneumophila. The results revealed that the D-4968 genome is larger than the L. pneumophila genome and has a gene order that is different from that of the L. pneumophila genome. Genes encoding structural components of type II, type IV Lvh, and type IV Icm/Dot secretion systems are conserved. In contrast, only 42/140 homologs of genes encoding L. pneumophila Icm/Dot substrates have been found in the D-4968 genome. L. longbeachae encodes numerous proteins with eukaryotic motifs and eukaryote-like proteins unique to this species, including 16 ankyrin repeat-containing proteins and a novel U-box protein. We predict that these proteins are secreted by the L. longbeachae Icm/Dot secretion system. In contrast to the L. pneumophila genome, the L. longbeachae D-4968 genome does not contain flagellar biosynthesis genes, yet it contains a chemotaxis operon. The lack of a flagellum explains the failure of L. longbeachae to activate caspase 1 and trigger pyroptosis in murine macrophages. These unique features of L. longbeachae may reflect adaptation of this species to life in soil. doi:10.1128/JB.01272-09

Legionellae colonize biofilms in building water systems, yet little is known about their interaction with the organisms in these microbial communities. The role of Legionella pneumophila type IV pili and the type II secretion pre-pilin peptidase was evaluated in a model biofilm system. L. pneumophila strains 130b (wild-type), BS100 (a type IV pili mutant) and NU243 (a pre-pilin peptidase mutant) were assessed for attachment and retention in an established biofilm. Strains 130b and NU243 colonized the biofilm at a similar level while BS100 attached at a tenfold lower level. Over time, NU243 dropped below the level of detection while BS100 remained in the biofilm throughout the course of the experiment. The wild-type strain decreased but remained at a considerably higher level than either of the mutants. Inclusion of amoebae with BS100 allowed for attachment and retention at a level similar to 130b. NU243, which displays reduced intracellular replication, was able to establish itself and persist in the presence of amoebae. Thus, type IV pili and the pre-pilin peptidase facilitate L. pneumophila colonization of biofilms but are not required in the presence of a host for intracellular replication. DOI: 10.1099/mic.0.2006/000497-0

Monochloramine disinfection of municipal water supplies is associated with decreased risk for Legionnaires' disease. We conducted a 2-year, prospective, environmental study to evaluate whether converting from chlorine to monochloramine for [...]

Research has been conducted on the Legionella pneumophila. The ability of this bacteria to survive in the potable-water biofilm without the association with Hertmannella vermiformis has been investigated and reported.

A novel strain of Legionella is isolated from a soil amoeba. In the laboratory, the bacteria multiplied inside Acanthamoeba polyphaga and proved to be pathogenic against this species. Characterization of the gene for the 16S ribosomal RNA identified this bacterial strain as belonging to the genus Legionella. However, serologic assays revealed that this is a distinct strain. Techniques in the isolation and characterization of Legionella from free-living amoeba are discussed.

The conjugative and virulence properties of an 85 MDa plasmid, designated pCH1, from Legionella pneumophila were studied. Mating experiments were then performed between strain CH-1 which harboured pCH1 and plasmid-less L. pneumophila recipients. The results show that pCH1 is self-transmissible by conjugation among serogroup 1 isolates of L. pneumophila, and that pCH1 does not contribute to the ability of L. pneumophila to enter or grow within eukaryotic cells.

Legionnaires' disease is caused by the bacteria Legionella pneumophila, which occurs commonly in nature. Experts believe that L. pneumophila can be transmitted to humans by inhalation of aerosols, which are composed of many tiny water droplets, or by aspiration into the respiratory tract of contaminated drinking water. But outbreaks of Legionnaires' disease have been documented in which these two sources of the bacteria were clearly not involved. One such outbreak of the disease is described; the only risk factor identified was exposure to an excavation and construction site. During May 1986, 27 people living in a rural county of Maryland were diagnosed with Legionnaires' disease; the symptoms were characteristic of pneumonia and two persons died from the illness. The bacteria were detected in the sputum of two patients and the lung tissue of a third. Antibody testing was used in diagnosing the other 24 patients. A case-control study was set up, and it was discovered that 12 out of 16 persons who developed the disease had visited a particular retail store during the two weeks before the onset of symptoms. Only 4 of 28 controls had been to the store. Employees at the store were also 3.63 times more likely to show high levels of antibodies to L. pneumophila than controls. It appears that the store's location next to the excavation and construction site led to the outbreak. During this time, a prolonged drought was occurring in the county. It is thought that heat and dry conditions can kill Legionella pneumophila, and it may be that in this case the bacteria were somehow protected from these conditions. (Consumer Summary produced by Reliance Medical Information, Inc.)

Abstract Background From June to November 2005, 18 cases of community-acquired Legionnaires' disease (LD) were reported in Rapid City South Dakota. We conducted epidemiologic and environmental investigations to identify the source of the outbreak. Methods We conducted a case-control study that included the first 13 cases and 52 controls randomly selected from emergency department records and matched on underlying illness. We collected information about activities of case-patients and controls during the 14 days before symptom onset. Environmental samples (n = 291) were cultured for Legionella. Clinical and environmental isolates were compared using monoclonal antibody subtyping and sequence based typing (SBT). Results Case-patients were significantly more likely than controls to have passed through several city areas that contained or were adjacent to areas with cooling towers positive for Legionella. Six of 11 case-patients (matched odds ratio (mOR) 32.7, 95% CI 4.7-∞) reported eating in Restaurant A versus 0 controls. Legionella pneumophila serogroup 1 was isolated from four clinical specimens: 3 were Benidorm type strains and 1 was a Denver type strain. Legionella were identified from several environmental sites including 24 (56%) of 43 cooling towers tested, but only one site, a small decorative fountain in Restaurant A, contained Benidorm, the outbreak strain. Clinical and environmental Benidorm isolates had identical SBT patterns. Conclusion This is the first time that small fountain without obvious aerosol-generating capability has been implicated as the source of a LD outbreak. Removal of the fountain halted transmission.

Legionnaires' disease (LD) is a serious and frequently fatal disease caused by a type of bacteria known as Legionella pneumophila. The symptoms include pneumonia, a dry cough, muscle aches and occasionally digestive disorders. Major organs, including the heart, may be damaged as the disease continues. When outbreaks of LD have occurred, the specific source of the bacteria has been sought; examples of confirmed sources include humidifiers, evaporative condensers, cooling towers, whirlpool spas, and respiratory therapy equipment. It has also been suggested that L. pneumophila might be transmitted through a shower, but no such case has been reported to date. The bacteria need nutrients in order to survive and multiply, and it has been found that they can live in water that contains live amoebae. At a hospital in South Dakota, there were 26 cases of hospital-acquired LD over a period of 3.5 years; 10 of the patients died. Investigation of these cases linked them to use of the showers; patients who took showers were at increased risk for contracting LD while those who took sponge-baths were at lower risk. It was suggested that the shower heads had been colonized by the bacteria, but replacement of these devices did not end the LD outbreak. It was concluded that persistent colonies of the bacteria survived in the hot water supply for the 3.5-year period. It also appeared that amoebae in the water supply helped the bacteria to survive. Further research will be needed to better understand the relationship between L. pneumophila bacteria and amoebae; disinfection methods that kill the amoebae may be effective at preventing Legionnaires' disease. (Consumer Summary produced by Reliance Medical Information, Inc.)