Infective endocarditis caused by Paenibacillus thiaminolyticus: a case report and review of literature

BACKGROUND: Paenibacillus constitutes a genus of gram-positive, facultatively anaerobic, rod-shaped bacteria that act as potentially opportunistic pathogens. With only a few documented case studies to date, Paenibacillus species are rarely the cause of a disease in humans. CASE SUMMARY: We report a case involving a 64-year-old male with known mild mitral regurgitation, who presented with fever and dyspnoea. Initially treated with empirical antibiotics, his blood cultures cultivated Paenibacillus thiaminolyticus, a previously unreported cause of endocarditis. Transoesophageal echocardiography demonstrated vegetations on the both leaflets of mitral valve along with severe mitral regurgitation, thus confirming a diagnosis of endocarditis. The patient was referred for cardiac surgery; however, the procedure was delayed due to complications related to a known hepatic cyst and additionally contraction of COVID-19 infection. The patient subsequently underwent mitral valve replacement without complications. DISCUSSION: Because of its rarity, guidelines to recommend specific antibiotics to treat Paenibacillus infective endocarditis are absent. To confirm the pathogen, molecular methods such as mass spectrometry or 16S rRNA sequencing are required. Early targeted antibiotic therapy and cardiac surgery are warranted to achieve good clinical outcomes.