Mycobacterium marinum as Cause of Dermatitis

A HIV-infected male with end stage renal disease presented with lower extremity stasis-related dermatitis. Discrete lesions were developing on his more proximal legs and on his distal upper extremities. A cutaneous exam revealed a moccasin distribution of scale bilaterally on his feet, and gross dystrophia of both great toenails. Fluid was collected from an abscess on his left arm and sent to the Microbiology Laboratory for cultures as well as to the Molecular Microbiology laboratory at the UWMC for PCR testing for bacteria, atypical mycobacteria and fungi.

The Auramine-O stain showed 1+ AFB on direct smear, but the culture did not grow any acid-fast organisms for over two weeks. Direct DNA extraction of the fluid and PCR amplification of the RNA polymerase (rpoB) gene fragment produced a DNA sequence matching 100% to Mycobacterium marinum in the NCBI nucleotide database. The next month, an organism grew in the AFB culture which was confirmed to be M. marinum by 16S sequence analysis, also performed at the Molecular Microbiology lab.

Please refer to Available Tests for more information about TSEXAM for AFB.