INFECTION BY MYCOBACTERIUM MARINUM: RELEVANCE OF EPIDEMIOLOGICAL HISTORY AND CLINICAL SUSPICION IN REFRACTORY CUTANEOUS LESIONS

Mycobacterium marinum is a slow-growing non-tuberculous mycobacterium well established as a pathogen in fish, causing skin and soft tissue infections in humans (“aquarium granuloma”) and potentially affecting deeper tissues. The disease most commonly occurs after exposure to freshwater (e.g., rivers), followed by brackish and seawater, especially in individuals with prior skin injury. Recreational swimmers, rescue teams, workers exposed to water, and flood victims are at increased risk. We describe the case of A.Z., a 71-year-old male with six months of right elbow bursitis, who had received multiple antimicrobial regimens (amoxicillin/clavulanate, cefuroxime, and linezolid) with persistent symptoms. A noteworthy laboratory finding was a reactive IGRA. His medical history included diabetes mellitus, dyslipidemia, mild coronary atherosclerotic disease, Barrett’s esophagus, asthma, nephrolithiasis, and degenerative lumbar disc disease; prior surgeries included inguinal hernia repair, blepharoplasty, rhinoplasty after a bicycle fall, and lower limb phlebectomy. The patient resides in Rio de Janeiro/RJ and practices cycling and swimming. After another therapeutic failure, he underwent surgical correction of olecranon bursitis, during which yellowish spongy material without exudate was collected and sent for analysis. Culture of the right elbow bursa was positive for Mycobacterium marinum . Treatment recommended for deep infections was initiated with two active agents, clarithromycin and ethambutol. This case highlights the importance of detailed medical history with attention to epidemiological exposure and the need to suspect NTM infection in lesions refractory to conventional antimicrobials for skin and soft tissue infections. It also underscores the fundamental role of surgical intervention combined with appropriate sample collection and microbiological analysis for diagnostic clarification.