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Legionnaires disease with bacteremic coinfection
Michael J Tan1, James S Tan, Thomas M File
1Department of Internal Medicine, Summa Health System, Akron, OH, USA. tanj@summa-health.org
Summary
Community-acquired pneumonia patients can have a hidden Legionella pneumophila coinfection. Early treatment should target both pneumococcus and Legionella species, especially in smokers.
Area of Science:
- Medical Microbiology
- Infectious Diseases
- Pulmonology
Background:
- Community-acquired pneumonia (CAP) is a common infection, often caused by bacteria like Streptococcus pneumoniae.
- Legionella pneumophila is an important cause of atypical pneumonia, diagnosed via urinary antigen or seroconversion.
- Coinfections can complicate diagnosis and treatment of pneumonia.
Observation:
- This study reviewed six patients with bacteremic CAP and unsuspected Legionella pneumophila coinfection.
- Diagnosis of Legionella was confirmed by urinary antigen (3 patients) or a four-fold rise in antibody titer (3 patients).
- Concurrent bacterial pathogens included Streptococcus pneumoniae (4 patients), Streptococcus pyogenes (1 patient), and Enterobacter cloacae (1 patient).
Findings:
- Legionella pneumophila coinfection was identified in patients presenting with bacteremic community-acquired pneumonia.
- The presence of L. pneumophila infection may have increased susceptibility to other bacterial bloodstream infections.
- Streptococcus pneumoniae was the most common co-infecting bacterium.
Implications:
- Clinicians should consider Legionella coinfection in patients with CAP, particularly in endemic areas and in smokers.
- Empiric antimicrobial therapy for CAP should include agents effective against both Streptococcus pneumoniae and Legionella species.
- Prompt diagnosis and appropriate treatment are crucial to improve outcomes in patients with pneumonia coinfections.