Fish Tank Granuloma Caused by Mycobacterium marinum

Fish Tank Granuloma Mycobacterium marinum is a slow-growing mycobacterium with an optimal growth temperature of 30°C. It most frequently causes skin and soft tissue infections in the extremities. Patients typically show clusters of nodules, ulcers, or verrucous plaques that may centripetally spread from the arms or legs in a sporotrichoid pattern – pulmonary infections, osteomyelitis, arthritis, and disseminated diseases are encountered to a lesser extent.

Many factors play important roles in causing M. marinum infections. These include prescription of local or systemic steroids or immunosuppressive agents, and structural lung diseases. Among these, the primary risk factor is exposure to aquatic environments or marine animals. Thus M. marinum infection is also known as “fish tank granuloma”.


Fish Tank Granuloma Caused by Mycobacterium marinum. (2012) PLoS ONE 7(7): e41296. doi:10.1371/journal.pone.0041296
Introduction: Mycobacterium marinum causes skin and soft tissue, bone and joint, and rare disseminated infections. In this study, we aimed to investigate the relationship between treatment outcome and antimicrobial susceptibility patterns. A total of 27 patients with M. marinum infections were enrolled.
Methods: Data on clinical characteristics and therapeutic methods were collected and analyzed. We also determined the minimum inhibitory concentrations of 7 antibiotics against 30 isolates from these patients.
Results: Twenty-seven patients received antimycobacterial agents with or without surgical debridement. Eighteen patients were cured, 8 failed to respond to treatment, and one was lost to follow-up. The duration of clarithromycin (147 vs. 28; p = 0.0297), and rifampicin (201 vs. 91; p = 0.0266) treatment in the cured patients was longer than that in the others. Surgical debridement was performed in 10 out of the 18 cured patients, and in 1 of another group (p = 0.0417). All the 30 isolates were susceptible to clarithromycin, amikacin, and linezolid; 29 (96.7%) were susceptible to ethambutol; 28 (93.3%) were susceptible to sulfamethoxazole; and 26 (86.7%) were susceptible to rifampicin. However, only 1 (3.3%) isolate was susceptible to doxycycline.
Discussion: Early diagnosis of the infection and appropriate antimicrobial therapy with surgical debridement are the mainstays of successful treatment. Clarithromycin and rifampin are supposed to be more effective agents.

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