Prosthetic valve infective endocarditis caused by Cutibacterium modestum: a case report

Background While Cutibacterium acnes is well known for its potential to cause acne vulgaris, postsurgical infections, and other human infections, few reports have described Cutibacterium modestum infections. Thus, the clinical characteristics of C. modestum as an infectious disease are not well understood. Herein, we describe the characteristics of a case of prosthetic valve infective endocarditis caused by C. modestum.Case summary An 81-year-old man was admitted to our hospital with fever, general fatigue, and appetite loss. His past medical history included aortic valve replacement surgery and coronary artery bypass grafting for aortic valve stenosis and angina pectoris. Physical examination on admission revealed a body temperature of 39.0 degrees C, blood pressure of 97/68 mmHg, and pulse rate of 101 b.p.m. Transthoracic echocardiography showed no prosthetic valve destruction or malfunction or obvious vegetation adhesion to the prosthetic or other valves. Bacteria initially identified as C. acnes were detected in two sets of anaerobic blood culture bottles collected upon admission. However, as the samples required 111 and 118 h to become blood culture-positive, the possibility of contaminating bacteria was high. Transoesophageal echocardiography revealed vegetation in the artificial valve. Repeated blood culture revealed the same bacteria; thus, contamination was ruled out, and the diagnosis of infective endocarditis was confirmed. Finally, 16S ribosomal RNA gene sequencing identified the detected bacteria as C. modestum rather than C. acnes.Discussion Including this case, only two cases of prosthetic valve infective endocarditis caused by C. modestum have been reported, the characteristics of which are still poorly understood.