A Novel, Nonaquatic Zoonotic Transmission of Mycobacterium marinum

Introduction: Mycobacterium marinum was first described in humans in 1954, known to infect fish species and contaminate water and fish products. Inoculation to humans occurs through injured skin resulting in the formation of a solitary nodule known as "fish tank granuloma." Disseminated infections have been reported in the immunocompromised and can present with extracutaneous manifestations such as arthritis and osteomyelitis. Nonaquatic transmission has not been previously reported. Case Presentation: A 63-year-old lady with rheumatoid arthritis and bronchiectasis was referred to dermatology with widespread soft dermal plaques, pustules, erosions, and necrotic wounds. Multiple bacterial and viral swabs were negative. A biopsy was performed that showed a neutrophilic dermatosis suggestive of Sweet's Syndrome. The patient initially improved with prednisolone, but subsequently deteriorated with a worsening rash, joint pains, and neutropenic sepsis. Repeat biopsies eventually revealed abundant acid-fast bacilli, later confirmed to be Mycobacterium marinum. Our patient had no history of exposure to aquatic organisms but had previously cared for an inland bearded dragon with an unknown illness. Although infection with M. marinum has been reported in reptiles, cases of nonaquatic zoonotic transmission have not been described in the literature. Conclusion: Mycobacterium marinum infection should be considered in patients with indicative clinical and histological features, especially in the immunocompromised, even in the absence of an obvious aquatic source of infection. Awareness of this entity could lead to earlier diagnoses and reduced morbidity and mortality.