A rare case of Mycobacterium abscessus subspecies abscessus prosthetic valve endocarditis and the clinical importance of inducible erm(41) gene testing

A 56-year-old man with a history of injection drug use and two prior episodes of native valve infective endocarditis presented with dyspnoea on exertion. Our preliminary work-up revealed bacteraemia with reported growth of 'Mycobacterium abscessus group' on multiple blood cultures. The patient was later found to have eustachian valve and prosthetic pulmonic valve endocarditis. Initially, he responded to standard antimycobacterial therapy for rapidly growing mycobacteria (RGM) with supporting laboratory susceptibilities. However, he later developed refractory disease and persistent bacteraemia in the setting of these alleged susceptible antibiotics. Further molecular testing revealed a functional and inducible erm(41) gene which confers macrolide resistance. A subspecies analysis of the M abscessus group revealed the subspecies to be abscessus. We present a challenging case of M abscessus subsp. abscessus bacteraemia and prosthetic valve endocarditis with further discussion on treatment and management of this infection along with the taxonomic complexity of this ubiquitous RGM.

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