Bacterial infiltration in structural heart valve disease.

Area of Science:

• Cardiology
• Infectious Diseases
• Molecular Biology

Background:

• Structural valvular heart disease (sVHD) encompasses a range of conditions from rheumatologic origins to post-infectious remodeling.
• Molecular genetic methods, particularly whole-metagenome analysis, can identify microbial agents in heart valve tissues without relying on cultivation.
• Understanding the microbial spectrum is crucial for elucidating the pathogenicity of sVHD.

Purpose of the Study:

• To assess the pathogen spectrum in heart valve tissue from patients with structural valvular heart disease (sVHD).
• To compare molecular genetic methods with traditional microbiological techniques for pathogen detection.
• To investigate the role of bacterial infiltration in the pathophysiology of sVHD.

Main Methods:

• Twenty-five sVHD patients were analyzed from an observational cohort.
• Explanted heart valves underwent microbiological examination, immunohistological structural analysis, and whole-metagenome sequencing.
• Sonication pretreatment was used for microbial cultivation in a subset of samples.

Main Results:

• Microbial cultivation detected Clostridium difficile, Enterococcus faecalis, Staphylococcus saccharolyticus, and Staphylococcus haemolyticus in four patients.
• Metagenome analysis revealed bacterial infiltration in 52% of the sVHD cases.
• The identified pathogens included both gram-positive and gram-negative bacteria, with intramural localization observed histologically.

Conclusions:

• Both microbiological and molecular methods are essential for comprehensive bacterial detection in calcified heart valves.
• Metagenome analysis provides valuable insights into the polymicrobial pathophysiology of sVHD.
• Results suggest that chronic inflammation or secondary bacterial infiltration may trigger or influence a portion of sVHD cases.