Legionella oakridgensis: laboratory diagnosis of a human infection

Correlation between bacterial microbiome and Legionella species in water from public bath facilities by 16S rRNA gene amplicon sequencing

Public bath facilities are a major source of Legionella infections in Japan. In this study, we performed 16S rRNA gene amplicon sequencing to characterize the bacterial community in bath and shower water from public bath facilities, along with chemical parameters, and investigated the effect of the bacterial microbiome on the presence of Legionella species. Although no significant difference in bacterial community richness was observed between bath and shower water samples, there was a remarkable difference in the bacterial community structure between them. Distance-based redundancy analysis revealed that several factors (free residual chlorine, pH, and conductivity) were correlated with the bacterial community in bath water. The most abundant bacterial genera in the samples were Pseudomonas (13.7%) in bath water and Phreatobacter (13.6%) in shower water, as indicated by the taxonomic composition, and the dominant bacteria differed between these environmental samples. Legionella pneumophila was the most frequently detected Legionella species, with additional 15 other Legionella species detected in water samples. In Legionella-positive water samples, several unassigned and uncultured bacteria were enriched together. In addition, the co-occurrence network showed that Legionella was strongly interconnected with two uncultured bacteria. Corynebacterium and Sphingomonas negatively correlated with Legionella species. The present study reveals the ecology of Legionella species, especially their interactions with other bacteria that are poorly understood to date.

IMPORTANCE

Public bath facilities are major sources of sporadic cases and outbreaks of Legionella infections. Recently, 16S rRNA gene amplicon sequencing has been used to analyze bacterial characteristics in various water samples from both artificial and natural environments, with a particular focus on Legionella bacterial species. However, the relationship between the bacterial community and Legionella species in the water from public bath facilities remains unclear. In terms of hygiene management, it is important to reduce the growth of Legionella species by disinfecting the water in public bath facilities. Our findings contribute to the establishment of appropriate hygiene management practices and provide a basis for understanding the potential health effects of using bath and shower water available in public bath facilities.

Presence of Viable, Clinically Relevant Legionella Bacteria in Environmental Water and Soil Sources of China

The distribution of pathogenic Legionella in the environmental soil and water of China has not been documented yet. In this study, Legionella was detected in 129 of 575 water (22.43%) and 41 of 442 soil samples (9.28%) by culture. Twelve Legionella species were identified, of which 11 were disease-associated. Of the Legionella-positive samples, 109 of 129 (84.50%) water and 29 of 41 (70.73%) soil were positive for L. pneumophila, which accounted for about 75% of Legionella isolates in both water and soil, suggesting L. pneumophila was the most frequent species. Soil showed a higher diversity of Legionella spp. as compared with water (0.6279 versus 0.4493). In contrast, serogroup (sg) 1 was more prevalent among L. pneumophila isolates from water than from soil (26.66% versus 12.21%). Moreover, many disease-associated sequence types (STs) of L. pneumophila were found in China. Intragenic recombination was acting on L. pneumophila from both water and soil. Phylogeny, population structure, and molecular evolution analyses revealed a probable existence of L. pneumophila isolates with a special genetic background that is more adaptable to soil or water sources and a small proportion of genetic difference between water and soil isolates. The detection of viable, clinically relevant Legionella demonstrates soil as another source for harboring and dissemination of pathogenic Legionella bacteria in China. Future research should assess the implication in public health with the presence of Legionella in the soil and illustrate the genetic and pathogenicity difference of Legionella between water and soil, particularly the most prevalent L. pneumophila. IMPORTANCE Pathogenic Legionella spp. is the causative agent of Legionnaires' disease (LD), and L. pneumophila is the most common one. Most studies have focused on L. pneumophila from water and clinical samples. However, the soil is another important reservoir for this bacterium, and the distribution of Legionella spp. in water and soil sources has not been compared and documented in China yet. Discovering the distribution of Legionella spp. and L. pneumophila in the two environments may help a deep understanding of the pathogenesis and molecular evolution of the bacterium. Our research systematically uncovered the distributions of Legionella spp. in different regions and sources (e.g., water and soil) of China. Moreover, phylogeny, population structure, and molecular evolution study revealed the possible existence of L. pneumophila with a special genetic background that is more adaptable to soil or water sources, and genetic difference may exist.

The mysterious illness that drove them to their knees - Ah, that Legionnaires' disease - A historical reflection of the work in Legionnaires' disease in New Zealand (1978 to mid-1990s) and the 'One Health' paradigm

And so, formed the basis for the song Legionnaires' disease (LD) composed by the legendry musician Bob Dylan shortly after this mysterious illness dramatically entered the clinical and epidemiological scene in July 1976 at an American hotel. Now more than forty years have passed since Legionella pneumophila, the causative agent of LD, was formally identified in 1977. Once the publicity associated with the outbreak subsided, there was the challenge to science and health professionals of what was an extremely complex and intriguing health concern. In the United States, the outbreak investigation that eventually solved the mystery had taken an array of surprising twists and turns. Globally, it revealed the strengths and weakness of countries' health systems in response to the outbreak from an unknown agent. Extensive international coverage of the outbreak also marked a turning point in journalism's efforts to hold officials accountable for their response to epidemics that had the potential to threaten the lives of hundreds of people. In 1979, New Zealand became an active participant in the international efforts towards increasing the understanding of infection caused by Legionella species and set up a centralized laboratory diagnostic service. By 1980 LD had become a notifiable disease making New Zealand one of the first countries globally to do so. This historical narrative in the decade or so from its recognition, provides a unique insight into how the One Health paradigm was instrumental in New Zealand's early response to LD in tandem with control strategies. The findings show that from 1979 the distribution of the Legionella species in New Zealand did not follow patterns observed in studies carried out globally.

Legionella oakridgensis ATCC 33761 genome sequence and phenotypic characterization reveals its replication capacity in amoebae

Legionella oakridgensis is able to cause Legionnaires' disease, but is less virulent compared to L. pneumophila strains and very rarely associated with human disease. L. oakridgensis is the only species of the family legionellae which is able to grow on media without additional cysteine. In contrast to earlier publications, we found that L. oakridgensis is able to multiply in amoebae. We sequenced the genome of L. oakridgensis type strain OR-10 (ATCC 33761). The genome is smaller than the other yet sequenced Legionella genomes and has a higher G+C-content of 40.9%. L. oakridgensis lacks a flagellum and it also lacks all genes of the flagellar regulon except of the alternative sigma-28 factor FliA and the anti-sigma-28 factor FlgM. Genes encoding structural components of type I, type II, type IV Lvh and type IV Dot/Icm, Sec- and Tat-secretion systems could be identified. Only a limited set of Dot/Icm effector proteins have been recognized within the genome sequence of L. oakridgensis. Like in L. pneumophila strains, various proteins with eukaryotic motifs and eukaryote-like proteins were detected. We could demonstrate that the Dot/Icm system is essential for intracellular replication of L. oakridgensis. Furthermore, we identified new putative virulence factors of Legionella.

Amoebal pathogens as emerging causal agents of pneumonia

Despite using modern microbiological diagnostic approaches, the aetiological agents of pneumonia remain unidentified in about 50% of cases. Some bacteria that grow poorly or not at all in axenic media used in routine clinical bacteriology laboratory but which can develop inside amoebae may be the agents of these lower respiratory tract infections (RTIs) of unexplained aetiology. Such amoebae-resisting bacteria, which coevolved with amoebae to resist their microbicidal machinery, may have developed virulence traits that help them survive within human macrophages, i.e. the first line of innate immune defence in the lung. We review here the current evidence for the emerging pathogenic role of various amoebae-resisting microorganisms as agents of RTIs in humans. Specifically, we discuss the emerging pathogenic roles of Legionella-like amoebal pathogens, novel Chlamydiae (Parachlamydia acanthamoebae, Simkania negevensis), waterborne mycobacteria and Bradyrhizobiaceae (Bosea and Afipia spp.).

Infection due to Legionella species other than L. pneumophila

In addition to Legionella pneumophila, 19 Legionella species have been documented as human pathogens on the basis of their isolation from clinical material. Like L. pneumophila, other Legionella species are inhabitants of natural and man-made aqueous environments. The major clinical manifestation of infection due to Legionella species is pneumonia, although nonpneumonic legionellosis (Pontiac fever) and extrapulmonary infection may occur. The majority of confirmed infections involving non-pneumophila Legionella species have occurred in immunosuppressed patients. Definitive diagnosis requires culture on selective media. Fluoroquinolones and newer macrolides are effective therapy. A number of nosocomial cases have occurred in association with colonization of hospital water systems; elimination of Legionella species from such systems prevents their transmission to susceptible patients. It is likely that many cases of both community-acquired and nosocomial Legionella infection remain undiagnosed. Application of appropriate culture methodology to the etiologic diagnosis of pneumonia is needed to further define the role of these organisms in disease in humans.

Isolation of Legionella oakridgensis from two patients with pleural effusion living in the same geographical area

Two cases of Legionnaire's disease caused by Legionella oakridgensis were diagnosed at the university hospital in Nantes, France. The two patients' isolates were identified by means of phenotyping and genotyping methods. Epidemiological investigations concluded that the first case was hospital acquired while the second case was considered community acquired.

Infection of macrophage-like cells by Legionella species that have not been associated with disease

We assessed the ability of Legionella species that have not been associated with disease to infect macrophage-like U937 cells. Two of fourteen species tested exhibited a 50% infective dose that was within I log unit of that of virulent L. pneumophila. Indeed, intracellular CFU of L. jamestowniensis and L. parisiensis increased 100-fold over a 72-h period. These data indicate that additional legionellae can flourish within phagocytes and therefore, can, if given the opportunity, cause disease.

Genus-specific epitope on the 60-kilodalton Legionella heat shock protein recognized by a monoclonal antibody

A monoclonal antibody (MAb) immunoglobulin G2a (2125) was produced against a 60-kDa Legionella heat shock protein (HSP), recognizing a unique epitope common to all species of the genus Legionella. The antibody reacted in the immunoblot with 59 Legionella species and serogroups that were tested and showed no cross-reactivity with other bacteria, including Acinetobacter spp., Bordetella spp., Pseudomonas spp., Mycobacterium spp., and Escherichia coli. Two other MAbs (2122 and 2130) reacted with the 60-kDa Legionella protein as well but showed different cross-reactivities with other gram-negative bacteria in the same molecular mass range. The genus-specific MAb 2125 as well as the cross-reacting MAbs 2122 and 2130 were shown to be reactive with the expressed protein of the cloned gene of the 60-kDa HSP of Legionella micdadei and Legionella pneumophila. These antibodies demonstrate that Legionella-specific and nonspecific epitopes are present on this protein. A sandwich enzyme-linked immunosorbent assay (ELISA) in which the genus-specific MAb is used both as a capture antibody and as a biotinylated second antibody has been established. With this test it is possible to detect Legionella whole cells, sonicated cells, and cell fractions containing the 60-kDa HSP. The main part of the 60-kDa HSP is found in the cytoplasmic fraction. The sandwich ELISA can be used to demonstrate the increased expression of the 60-kDa protein in Legionella cells following heat shock as well as marked differences in the detection of the 60-kDa HSP on whole cells of different Legionella strains. The high specificity and sensitivity of the sandwich ELISA for sonicated cells might be very useful to screen on a genus level for Legionella cells or the 60-kDa antigen in environmental isolates or body fluids of patients.

Cellular fatty acid compositions and isoprenoid quinone contents of 23 Legionella species

The cellular fatty acid compositions and ubiquinone contents of 182 Legionella strains representing 23 species were determined by capillary gas-liquid chromatography and reverse-phase high-performance liquid chromatography, respectively. Except for the type strain of Legionella erythra (ATCC 35303T), all Legionella species contained large (40 to 90%) amounts of branched-chain fatty acids and only trace to small (less than 0.5 to 5%) amounts of ester-linked hydroxy acids. The 23 species were placed in three major fatty acid groups on the basis of differences in the relative amounts of 14-methylpentadecanoic (Ci16:0), hexadecanoic (C16:1), and 12-methyltetradecanoic (Ca15:0) acids. All Legionella species contained ubiquinones with 9 to 14 isoprene units in the side chains and were divided into five different ubiquinone groups. The species were further differentiated into 16 groups on the basis of qualitative and quantitative differences in their fatty acid compositions and ubiquinone contents. Both of these chemical characteristics can be used to distinguish Legionella species from other gram-negative bacteria and rapidly and accurately identify suspected isolates before serologic and other tests are done.