Water ecology of Legionella and protozoan: environmental and public health perspectives

Borella, Paola; Guerrieri, Elisa; Marchesi, Isabella; Bondi, Moreno; Messi, Patrizia

doi:10.1016/s1387-2656(05)11011-4

Cited by 116 publications

(74 citation statements)

References 123 publications

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“…In addition to L. pneumophila, 19 species are documented as human pathogens on the basis of their isolation from clinical specimens (2). LD can affect people both in the community (3) and in the hospital and, in both settings, can occur in outbreaks (4,5). The true incidence of LD is difficult to assess, because the bacterial etiology for community-acquired pneumonia (CAP) is generally not documented in clinical practice.…”

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confidence: 99%

Diagnostic Accuracy of PCR Alone and Compared to Urinary Antigen Testing for Detection of Legionella spp.: a Systematic Review

et al. 2016

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bThe diagnosis of Legionnaires' disease (LD) is based on the isolation of Legionella spp., a 4-fold rise in antibodies, a positive urinary antigen (UA), or direct immunofluorescence tests. PCR is not accepted as a diagnostic tool for LD. This systematic review assesses the diagnostic accuracy of PCR in various clinical samples with a direct comparison versus UA. We included prospective or retrospective cohort and case-control studies. Studies were included if they used the Centers for Disease Control and Prevention consensus definition criteria of LD or a similar one, assessed only patients with clinical pneumonia, and reported data for all true-positive, false-positive, true-negative, and false-negative results. Two reviewers abstracted data independently. Risk of bias was assessed using Quadas-2. Summary sensitivity and specificity values were estimated using a bivariate model and reported with a 95% confidence interval (CI). Thirty-eight studies were included. A total of 653 patients had confirmed LD, and 3,593 patients had pneumonia due to other pathogens. The methodological quality of the studies as assessed by the Quadas-2 tool was poor to fair. The summary sensitivity and specificity values for diagnosis of LD in respiratory samples were 97.4% (95% CI, 91.1% to 99.2%) and 98.6% (95% CI, 97.4% to 99.3%), respectively. These results were mainly unchanged by any covariates tested and subgroup analysis. The diagnostic performance of PCR in respiratory samples was much better than that of UA. Compared to UA, PCR in respiratory samples (especially in sputum samples or swabs) revealed a significant advantage in sensitivity and an additional diagnosis of 18% to 30% of LD cases. The diagnostic performance of PCR in respiratory samples was excellent and preferable to that of the UA. Results were independent on the covariate tested. PCR in respiratory samples should be regarded as a valid tool for the diagnosis of LD.) is a life-threatening pulmonary infection. The most common species causing clinical disease in humans is Legionella pneumophila (1). In addition to L. pneumophila, 19 species are documented as human pathogens on the basis of their isolation from clinical specimens (2). LD can affect people both in the community (3) and in the hospital and, in both settings, can occur in outbreaks (4, 5). The true incidence of LD is difficult to assess, because the bacterial etiology for community-acquired pneumonia (CAP) is generally not documented in clinical practice. LD cannot be differentiated clinically or radiographically from CAP caused by other bacterial pathogens (6). As Legionella spp. are obligatory intracellular bacteria, they are unaffected by beta-lactam antibiotics and require specific treatment with high-dose quinolones or macrolides (7). Treatment providing coverage against Legionella spp. has been shown to improve clinical success (8). Thus, early diagnosis of LD is important and can have an effect on both public health and management in hospitals (9, 10).Conventional methods for the diagnosis of LD ...

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Diagnostic Accuracy of PCR Alone and Compared to Urinary Antigen Testing for Detection of Legionella spp.: a Systematic Review

et al. 2016

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“…In natural hosts and in certain mammalian cell lines, L. pneumophila displays a developmental cycle in which replicating bacteria differentiate into metabolically dormant cyst-like forms that enable the bacteria to survive for extended periods in a highly infectious state (24,28). Thus, protozoan hosts not only serve as a reservoir for bacterial amplification but also prepare the pathogen for stresses that may be encountered in new hosts, including humans (9,19,28,71).…”

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Compensatory Functions of Two Alkyl Hydroperoxide Reductases in the Oxidative Defense System ofLegionella pneumophila

LeBlanc¹,

Davidson

Hoffman

2006

J Bacteriol

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Legionella pneumophila expresses two catalase-peroxidase enzymes that exhibit strong peroxidatic but weak catalatic activities, suggesting that other enzymes participate in decomposition of hydrogen peroxide (H 2 O 2 ). Comparative genomics revealed that L. pneumophila and its close relative Coxiella burnetii each contain two peroxide-scavenging alkyl hydroperoxide reductase (AhpC) systems: AhpC1, which is similar to the Helicobacter pylori AhpC system, and AhpC2 AhpD (AhpC2D), which is similar to the AhpC AhpD system of Mycobacterium tuberculosis. To establish a catalatic function for these two systems, we expressed L. pneumophila ahpC1 or ahpC2 in a catalase/peroxidase mutant of Escherichia coli and demonstrated restoration of H 2 O 2 resistance by a disk diffusion assay. ahpC1::Km and ahpC2D::Km chromosomal deletion mutants were two-to eightfold more sensitive to H 2 O 2 , tert-butyl hydroperoxide, cumene hydroperoxide, and paraquat than the wild-type L. pneumophila, a phenotype that could be restored by trans-complementation. Reciprocal strategies to construct double mutants were unsuccessful. Mutant strains were not enfeebled for growth in vitro or in a U937 cell infection model. Green fluorescence protein reporter assays revealed expression to be dependent on the stage of growth, with ahpC1 appearing after the exponential phase and ahpC2 appearing during early exponential phase. Quantitative real-time PCR showed that ahpC1 mRNA levels were ϳ7-to 10-fold higher than ahpC2D mRNA levels. However, expression of ahpC2D was significantly increased in the ahpC1 mutant, whereas ahpC1 expression was unchanged in the ahpC2D mutant. These results indicate that AhpC1 or AhpC2D (or both) provide an essential hydrogen peroxide-scavenging function to L. pneumophila and that the compensatory activity of the ahpC2D system is most likely induced in response to oxidative stress.

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“…Many of the water distribution networks are faced with massive leakages, irregular supply and low water pressure; these factors create avenue for easy water contamination (Marin, 2009). Implicitly, much of the water prior to being consumed at distal sites are already contaminated with pathogenic bacteria; a challenge that must be avoided from the onset as a step in achieving Legionella control (Borella et al, 2005;Rangel et al, 1999;WHO, 2007).…”

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confidence: 99%

Evidence based review of Legionella elimination in building water systems

Sedzro¹,

Banu²,

Akrong³

2017

Int. J. Water Res. Environ. Eng.

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Legionnaires disease can be acquired through exposure to Legionella pneumophila, a gram-negative bacteria ubiquitous in both natural and engineered water systems. Over the years, a number of disinfection techniques notably, chlorination, ozonation, thermal, UV and copper-silver ionization have been employed across different kinds of engineered water systems with diverse measures of success. Available evidence portends, most of the aforementioned techniques often have to be combined to achieve long-term efficacy. Remarkably, albeit the extensive research and reportage on Legionnaires outbreak in the developed world, very few studies have been carried out with regards to Africa. We reviewed existing literature on the application of the aforementioned techniques in buildings. Our study concurs with earlier studies; most of the disinfection techniques will have to be combined to achieve the desired efficacy. We found very scanty studies on Legionella or reportage of its outbreak within Africa. Our study also found very little in terms of any of the techniques been applied with the specific aim of reducing Legionella proliferation in engineered water systems within Africa. This is alarming, especially, on a continent where several communities have little or no access to quality water and healthcare. In light of the above, stronger measures such as sensitization, pro perly managed water distribution systems, as well as policies aimed at enforcing national and international guidelines on Legionella control is recommended.

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Water ecology of Legionella and protozoan: environmental and public health perspectives

Cited by 116 publications

References 123 publications

Diagnostic Accuracy of PCR Alone and Compared to Urinary Antigen Testing for Detection of Legionella spp.: a Systematic Review

Diagnostic Accuracy of PCR Alone and Compared to Urinary Antigen Testing for Detection of Legionella spp.: a Systematic Review

Compensatory Functions of Two Alkyl Hydroperoxide Reductases in the Oxidative Defense System ofLegionella pneumophila

Evidence based review of Legionella elimination in building water systems

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