Rello Jordi, Allam Camille, Ruiz-Spinelli Alfonsina, Jarraud Sophie
Global Health ECore, Vall d'Hebron Institut of Research (VHIR), Barcelona, Spain.
Formation Recherche Evaluation (FOREVA) Research Group, CHU Nîmes, Nîmes, France.
Ann Intensive Care. 2024 Apr 2;14(1):51. doi: 10.1186/s13613-024-01252-y.
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.
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.
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.
军团菌病（LD）是社区获得性肺炎（CAP）的常见病因，但常被漏诊，不过尿液抗原检测（UAT）的快速检测以及分子检测技术的进步已改善了诊断情况。几乎三分之一的LD病例需要入住重症监护病房（ICU），死亡率在4%至40%之间。本综述旨在探讨该疾病研究的最新进展，并提供重症LD诊断、发病机制及管理的最新情况。
近年来，由于具有危险因素的患者数量增加，尤其是免疫抑制患者数量增加，以及诊断方法的改进，LD在全球的总体发病率有所上升。尽管LD仅占所有病因所致CAP的约5%，但它是需要入住ICU的CAP的三大最常见病因之一。尽管进行了适当的抗菌治疗，ICU患者、免疫功能低下患者或有医院感染源的LD患者的死亡率仍可达到40%。关于发病机制，尚未发现军团菌特异性毒力因子与疾病严重程度相关；然而，最近的报告发现，在最严重的病例中，肺部军团菌DNA载量很高，免疫反应和肺部微生物群存在损害。临床表现包括需要呼吸和/或血流动力学支持的严重肺损伤、肺外症状和非特异性实验室检查结果。由于UAT的广泛应用和能够检测所有嗜肺军团菌血清群的分子方法的发展，LD的诊断方法有所改进。目前的治疗基于大环内酯类、喹诺酮类或两者联合使用，重症病例需延长治疗时间。
许多因素会影响LD的死亡率，如入住ICU、基础免疫状态和感染的医院感染源。宿主免疫反应（过度炎症和/或免疫麻痹）也可能与病情加重有关。鉴于LD的发病率在上升，对严重程度特异性生物标志物的研究可能会引起极大兴趣。如今需要进一步评估以比较不同治疗方案和/或评估针对宿主的疗法。
