Abstract
Background. Non-tuberculous mycobacterial infective endocarditis (NTM-IE) is an uncommon but increasingly recognized aetiology of culture-negative endocarditis, particularly in the context of healthcare exposure. Rapidly growing non-tuberculous mycobacteria (NTM) species present significant diagnostic and therapeutic challenges due to their indolent nature and clinical similarity to tuberculosis. Case summary. We describe a case series of three patients with native valve infective endocarditis caused by rapidly growing NTM following recent percutaneous coronary intervention. All patients initially presented with prolonged fever and systemic inflammatory signs, and routine microbiological workup results were negative. The diagnosis was based on repeated blood and/or urine cultures with the detection of rapidly growing NTM, exclusion of Mycobacterium tuberculosis by PCR analysis and echocardiography demonstrating valvular vegetations. Cultures were performed on consecutive days at a single reference laboratory according to established protocols to reduce the risk of sample contamination. Species-level identification was not feasible because of limited resources. All patients received combination antimicrobial therapy guided by the available susceptibility data and expert consultation. Despite multidrug treatment, clinical outcomes were poor in these cases. Two patients died before definitive surgical intervention could be performed, and one patient died during the induction of the valve replacement surgery. Conclusion. This case series highlights the difficulties in diagnosing NTM-IE and its high mortality rate. NTM infection should be considered in patients with chronic fever after invasive cardiovascular procedures or with prolonged culture-negative endocarditis. Medical therapy is frequently inadequate, and a combined medical-surgical approach may be necessary.