Diagnosis of Mycobacterium marinum Infection Based on Seroconversion of QuantiFERON-TB Gold Test

Mycobacterium marinum is a slow-growing photochromatic acid fast bacilli (AFB). Following exposure of injured skin to fish tanks and other aquatic bodies, it usually causes indolent skin and soft tissue infections. Incubation period differs but it is generally long; hence, diagnosis is often missed leading to delay in treatment. Obtaining proper history along with histopathology and cultures leads to diagnosis. There is evidence of cross-reactivity of M. marinum with QuantiFERON-TB gold test. In patients without risk factors for tuberculosis, recent seroconversion may provide a clue to diagnosis and eliminate differentials. We present a case of M. marinum skin and soft tissue infection diagnosed based on seroconversion of QuantiFERON-TB gold test in an immunocompromised patient. This was confirmed by AFB culture after six weeks.