Pleural fluid microbiota as a biomarker for malignancy and prognosis

Area of Science:

• Microbiology
• Oncology
• Pulmonology

Background:

• Malignant pleural effusions (MPE) are a common complication of cancer, associated with poor prognosis.
• Current diagnostic and prognostic tools for MPE focus on cellular and cell-free components.
• The role of the pleural fluid microbiome in MPE remains largely unexplored.

Purpose of the Study:

• To investigate the unique microbial composition of MPE.
• To compare the MPE microbiome with that of benign and paramalignant pleural effusions.
• To identify microbial signatures associated with MPE diagnosis, primary cancer site, and patient mortality.

Main Methods:

• 16S rRNA gene sequencing was performed on 165 pleural fluid samples.
• Samples included benign (n=16), paramalignant (n=21), MPE-Lung (n=57), MPE-Other (n=22), and Mesothelioma (n=49) effusions.
• Comparative analysis of microbial composition across different effusion types was conducted.

Main Results:

• Significant compositional differences were observed in pleural effusions from non-malignant, paramalignant, and malignant conditions.
• MPE samples showed differential enrichment of bacterial taxa based on the primary malignancy site.
• MPE-Lung and Mesothelioma were associated with oral and gut commensal bacteria (e.g., Rickettsiella, Ruminococcus).
• Mortality in MPE-Lung was linked to enrichment of specific bacteria (e.g., Methylobacterium, Blattabacterium).

Conclusions:

• The microbiome of pleural effusions varies significantly with disease state (benign, paramalignant, malignant).
• Specific bacterial communities in MPE correlate with the primary cancer site and patient survival.
• These findings highlight the potential role of host-microbiome interactions in carcinogenesis and MPE progression.