Increased Incidence of Legionellosis after Improved Diagnostic Methods, New Zealand, 2000–2020

Graham, Frances F.; Harte, David; Zhang, Jingyan; Fyfe, Caroline; Baker, Michael G

doi:10.3201/eid2906.221598

Cited by 3 publications

(4 citation statements)

References 20 publications

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“…Reported legionellosis incidence may increase in future decades as diagnostic methods such as PCR – which can detect species and serogroups other than L. pneumophila serogroup 1 – become more widespread. This shift was demonstrated in a New Zealand analysis that found a marked increase in incidence corresponding with the uptake of molecular diagnostic methods [ 36 ]; future studies in the USA will need to account for the impact of these changes.…”

Section: Discussionmentioning

confidence: 99%

Legionellosis on the rise: A scoping review of sporadic, community-acquired incidence in the United States

Moffa,

Rock,

Galiatsatos

et al. 2023

Epidemiol. Infect.

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Over the past two decades, the incidence of legionellosis has been steadily increasing in the United States though there is noclear explanation for the main factors driving the increase. While legionellosis is the leading cause of waterborne outbreaks in the US, most cases are sporadic and acquired in community settings where the environmental source is never identified. This scoping review aimed to summarise the drivers of infections in the USA and determine the magnitude of impact each potential driver may have. A total of 1,738 titles were screened, and 18 articles were identified that met the inclusion criteria. Strong evidence was found for precipitation as a major driver, and both temperature and relative humidity were found to be moderate drivers of incidence. Increased testing and improved diagnostic methods were classified as moderate drivers, and the ageing U.S. population was a minor driver of increasing incidence. Racial and socioeconomic inequities and water and housing infrastructure were found to be potential factors explaining the increasing incidence though they were largely understudied in the context of non-outbreak cases. Understanding the complex relationships between environmental, infrastructure, and population factors driving legionellosis incidence is important to optimise mitigation strategies and public policy.

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Section: Discussionmentioning

confidence: 99%

Legionellosis on the rise: A scoping review of sporadic, community-acquired incidence in the United States

Moffa,

Rock,

Galiatsatos

et al. 2023

Epidemiol. Infect.

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“…Legionella pneumophila (Lp) is the most frequent cause of disease (mostly the serogroup (sg) 1 (Lp1), followed by sg3 and sg6), which account for 80–90% of cases in Europe and in the US [ 4 ]. In Australia and New Zealand the predominant species is L. longbeachae [ 5 , 6 ] which accounts for up to 51% of causative agents for LD [ 6 ], while Lp represents 31% [ 5 , 6 ]. This heterogeneous distribution may be attributed to several factors: for example, in New Zealand there is a more systematic use of Legionella screening by PCR, and clusters of L. longbeachae infections are seen in early spring‒summer and might be linked to increased outdoor activity, such as gardening in the warmer months [ 6 ].…”

Section: Epidemiologymentioning

confidence: 99%

“…In Australia and New Zealand the predominant species is L. longbeachae [ 5 , 6 ] which accounts for up to 51% of causative agents for LD [ 6 ], while Lp represents 31% [ 5 , 6 ]. This heterogeneous distribution may be attributed to several factors: for example, in New Zealand there is a more systematic use of Legionella screening by PCR, and clusters of L. longbeachae infections are seen in early spring‒summer and might be linked to increased outdoor activity, such as gardening in the warmer months [ 6 ]. However, the exact reason for its predominance remains unknown as L. longbeachae strains display a high genetic diversity, probably indicating the presence of multiple sources of infection [ 7 ].…”

Section: Epidemiologymentioning

confidence: 99%

“…The main sources of contamination are water network systems, spas and cooling towers [ 10 ]. Interestingly, L. longbeachae disease has been associated with gardening and the use of potting soil, commercial bagged soil, and compost materials containing this bacterium [ 6 , 11 ], and L. anisa with dental practices [ 12 ]. Risk factor analysis reveals that temperatures > 20 ℃ are a significant risk factor for Legionella colonisation in dental chair equipment.…”

Section: Epidemiologymentioning

confidence: 99%

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Severe Legionnaires’ disease

Rello,

Allam,

Ruiz-Spinelli

et al. 2024

Ann. Intensive Care

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Background Legionnaires’ disease (LD) is a common but under-diagnosed cause of community-acquired pneumonia (CAP), although rapid detection of urine antigen testing (UAT) and advances in molecular testing have improved the diagnosis. LD entails intensive care unit (ICU) admission in almost one-third of cases, and the mortality rate ranges from 4% to 40%. This review aims to discuss recent advances in the study of this condition and to provide an update on the diagnosis, pathogenesis and management of severe LD. Results The overall incidence of LD has increased worldwide in recent years due to the higher number of patients with risk factors, especially immunosuppression, and to improvements in diagnostic methods. Although LD is responsible for only around 5% of all-cause CAP, it is one of the three most common causes of CAP requiring ICU admission. Mortality in ICU patients, immunocompromised patients or patients with a nosocomial source of LD can reach 40% despite appropriate antimicrobial therapy. Regarding pathogenesis, no Legionella-specific virulence factors have been associated with severity; however, recent reports have found high pulmonary Legionella DNA loads, and impairments in immune response and lung microbiome in the most severe cases. The clinical picture includes severe lung injury requiring respiratory and/or hemodynamic support, extrapulmonary symptoms and non-specific laboratory findings. LD diagnostic methods have improved due to the broad use of UAT and the development of molecular methods allowing the detection of all Lp serogroups. Therapy is currently based on macrolides, quinolones, or a combination of the two, with prolonged treatment in severe cases. Conclusions Numerous factors influence the mortality rate of LD, such as ICU admission, the underlying immune status, and the nosocomial source of the infection. The host immune response (hyperinflammation and/or immunoparalysis) may also be associated with increased severity. Given that the incidence of LD is rising, studies on specific biomarkers of severity may be of great interest. Further assessments comparing different regimens and/or evaluating host-directed therapies are nowadays needed. Graphical Abstract

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Inhibition and evasion of neutrophil microbicidal responses by Legionella longbeachae

Hanford,

Price,

Uriarte

et al. 2024

mBio

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Legionella species evade degradation and proliferate within alveolar macrophages as an essential step for the manifestation of disease. However, most intracellular bacterial pathogens are restricted in neutrophils, which are the first line of innate immune defense against invading pathogens. Bacterial degradation within neutrophils is mediated by the fusion of microbicidal granules to pathogen-containing phagosomes and the generation of reactive oxygen species (ROS) by the phagocyte NADPH oxidase complex. Here, we show that human neutrophils fail to trigger microbicidal processes and, consequently, fail to restrict L. longbeachae . In addition, neutrophils infected with L. longbeachae fail to undergo a robust pro-inflammatory response, such as degranulation and IL-8 production. Here, we identify three strategies employed by L. longbeachae for evading restriction by neutrophils and inhibiting the neutrophil microbicidal response to other bacteria co-inhabiting in the same cell. First, L. longbeachae excludes the cytosolic and membrane-bound subunits of the phagocyte NADPH oxidase complex from its phagosomal membrane independent of the type 4 secretion system (T4SS). Consequently, infected neutrophils fail to generate robust ROS in response to L. longbeachae . Second, L. longbeachae impedes the fusion of azurophilic granules to its phagosome and the phagosomes of bacteria co-inhabiting the same cell through T4SS-independent mechanisms. Third, L. longbeachae protects phagosomes of co-inhabiting bacteria from degradation by ROS through a trans -acting T4SS-dependent mechanism. Collectively, we conclude that L. longbeachae evades restriction by human neutrophils via T4SS-independent mechanisms and utilizes trans -acting T4SS-dependent mechanisms for inhibition of neutrophil ROS generation throughout the cell cytosol. IMPORTANCE Legionella longbeachae is commonly found in soil environments where it interacts with a wide variety of protist hosts and microbial competitors. Upon transmission to humans , L. longbeachae invades and replicates within alveolar macrophages, leading to the manifestation of pneumonia. In addition to alveolar macrophages, neutrophils are abundant immune cells acting as the first line of defense against invading pathogens. While most intracellular bacterial species are killed and degraded by neutrophils, we show that L. longbeachae evades degradation. The pathogen impairs the major neutrophils’ microbicidal processes, including the fusion of microbicidal granules to the pathogen-containing vacuole. By inhibiting of assembly of the phagocyte NADPH oxidase complex, the pathogen blocks neutrophils from generating microbicide reactive oxygen species. Overall, L. longbeachae employs unique virulence strategies to evade the major microbicidal processes of neutrophils.

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Increased Incidence of Legionellosis after Improved Diagnostic Methods, New Zealand, 2000–2020

Cited by 3 publications

References 20 publications

Legionellosis on the rise: A scoping review of sporadic, community-acquired incidence in the United States

Legionellosis on the rise: A scoping review of sporadic, community-acquired incidence in the United States

Severe Legionnaires’ disease

Inhibition and evasion of neutrophil microbicidal responses by Legionella longbeachae

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