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.

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.

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