# Intraoperative sampling for postoperative metagenomic next-generation sequencing to guide biofilm-targeted therapy for Cutibacterium acnes infective endocarditis complicated by ruptured sinus of Valsalva aneurysm: a case report

## TL;DR

A rare case shows how combining surgery with advanced DNA sequencing helped diagnose and treat a hard-to-detect heart infection caused by Cutibacterium acnes.

## Contribution

Demonstrates the use of intraoperative mNGS and biofilm-targeted therapy for diagnosing and treating C. acnes infective endocarditis.

## Key findings

- mNGS identified C. acnes in a culture-negative case with high sequence reads and coverage.
- Switching to biofilm-targeted antibiotics led to normalization of inflammatory markers and full recovery.
- Early surgical debridement and repair were crucial for successful treatment and no recurrence at 12 months.

## Abstract

Cutibacterium acnes is an easily overlooked pathogen in infective endocarditis (IE) due to its slow growth, propensity for biofilm formation, and high rate of culture-negative results. When complicated by structural heart disease such as a ruptured sinus of Valsalva aneurysm (RSVA), its indolent course can lead to severe hemodynamic compromise.

A 35-year-old male with a known ventricular septal defect (VSD) and unruptured aortic sinus aneurysm presented with persistent fever and progressive heart failure (NYHA class IV). Echocardiography revealed a ruptured right coronary sinus of Valsalva aneurysm (RCSVA) into the right ventricular outflow tract (RVOT) with a large vegetation. Blood cultures were negative. After 6 days of ineffective empirical antibiotic therapy, emergency surgery was performed to resect the aneurysm and vegetation and repair the cardiac structures. Intraoperatively, a vegetation sample was collected for metagenomic next-generation sequencing (mNGS). Postoperatively, mNGS identified Cutibacterium acnes with high sequence reads (1,284) and coverage (47.62%), enabling a definitive diagnosis. Pathology confirmed microcolonies and necrotic inflammation. The antibiotic regimen was switched to a regimen with potential activity against biofilms with oral doxycycline and intravenous clindamycin for 6 weeks. The patient's inflammatory markers normalized, and cardiac function recovered to NYHA class I, with no recurrence at 12-month follow-up.

This case highlights the diagnostic synergy of intraoperative histopathology and mNGS for pathogen identification, underscores the rationale for biofilm-conscious adjuvant therapy, and reaffirms the crucial role of early surgical debridement and repair in achieving cure.