Mycobacterium marinum infection from a tropical fish tank. Treatment with trimethoprim and sulphamethoxazole.

A paronychial granuloma on the left thumb, in a man who kept tanks of tropical fish, was followed by cutaneous nodules on the left upper limb and tender lymph nodes in the left axilla. Mycobacterium marinum was isolated from the lesion on the thumb and also from the tank water. Subsidence of the lesions followed administration of trimethoprim and sulphamethoxazole.