An adult male presented to an infectious diseases clinic with lymphangitis of the left upper extremity, showing nodules ascending the dorsal aspect to the medial aspect of his left hand up to the elbow. The fingers were macerated and picked open at the nail borders on all ten digits. A biopsy from the skin of his left forearm was ordered, which was sent to the microbiology laboratory for AFB and fungal cultures, with a suspicion of atypical AFB.
The fungal culture was negative. The AFB culture grew acid-fast bacilli out of the broth only, which was sent to the Molecular Microbiology laboratory at the UWMC for identification by sequence analysis. PCR of the isolate produced a 16s sequence that matched 100% to Mycobacterium marinum.
It was revealed that the patient had been regularly exposed to aquarium water while cleaning numerous fish tanks and terrariums in his home. The patient was treated with a four-month course of erythromycin, rifampin and trimethoprim, and has since seen the nodules decrease in number and size.
Please refer to Available Tests for more information about AFB Sequencing.