Community-Acquired Legionella pneumophila Pneumonia: A Case-Control Study in Adult Inpatients from 2019 to 2024

Area of Science:

• Infectious Diseases
• Pulmonology
• Clinical Microbiology

Background:

• Legionella pneumophila (L. pneumophila) is a common cause of community-acquired pneumonia, often linked to environmental sources.
• High-risk individuals, including those over 50, immunocompromised, or with pre-existing conditions, are particularly susceptible.
• This study investigates factors associated with L. pneumophila community acquisition in hospitalized adult patients with pneumonitis.

Purpose of the Study:

• To identify clinical and laboratory factors associated with Legionella pneumophila community-acquired pneumonia.
• To understand the role of comorbidities in L. pneumophila infections.
• To inform early detection and treatment strategies for L. pneumophila pneumonia.

Main Methods:

• A case-control study involving 140 hospitalized adult patients with pneumonitis.
• Data collection included demographics, clinical, laboratory, and microbiological information.
• Legionella pneumophila detection utilized urinary antigen testing and the BioFire FilmArray Pneumonia Panel within 48 hours of admission.

Main Results:

• Comorbidities, particularly heart failure and smoking, were significantly associated with L. pneumophila presence.
• Patients with L. pneumophila pneumonia exhibited lower blood sodium, phosphate, and platelet levels.
• Elevated levels of LDH, CRP, AST, and ALT were observed in L. pneumophila positive patients.
• Levofloxacin was the most common therapy administered.

Conclusions:

• Early detection of L. pneumophila is critical, especially in patients with elevated CRP, hypophosphatemia, or heart failure.
• Prompt treatment with macrolides and fluoroquinolones is essential to reduce mortality in L. pneumophila infected patients.
• Identifying risk factors and specific laboratory markers aids in timely diagnosis and management.