Mycobacterium Marinum

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Medical Author:

Nili N. Alai, MD, FAAD

Nili N. Alai, MD, FAAD

Dr. Alai is an actively practicing medical and surgical dermatologist in south Orange County, California. She has been a professor of dermatology and family medicine at the University of California, Irvine since 2000. She is U.S. board-certified in dermatology, a 10-year-certified fellow of the American Academy of Dermatology, and Fellow of the American Society of Mohs Surgery.

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Medical Editor:

Frederick Hecht, MD, FAAP, FACMG

Frederick Hecht, MD, FAAP, FACMG

Frederick Hecht, MD, lives in Scottsdale, Arizona. Dr. Hecht is a Pediatrician and Medical Geneticist and is certified by both the American Boards of Pediatrics and Medical Genetics. Dr. Hecht was born and raised in Baltimore and attended Dartmouth College in Hanover, N.H. and the Sorbonne at the University of Paris receiving his BA degree cum laude with distinction from Dartmouth.

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Medical Editor:

William C. Shiel Jr., MD, FACP, FACR

William C. Shiel Jr., MD, FACP, FACR

Dr. Shiel received a Bachelor of Science degree with honors from the University of Notre Dame. There he was involved in research in radiation biology and received the Huisking Scholarship. After graduating from St. Louis University School of Medicine, he completed his Internal Medicine residency and Rheumatology fellowship at the University of California, Irvine. He is board-certified in Internal Medicine and Rheumatology.

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Mycobacterium marinum (M. marinum) is a slow-growing atypical bacteria that is commonly found in bodies of fresh or saltwater in many parts of the world. Skin infections with Mycobacterium marinum in humans are overall relatively uncommon and are usually acquired from contact with aquariums or fish. Most infections occur following skin exposure to the bacteria through a small cut or skin scrape. The first signs of infection with M. marinum include a reddish or tan skin bump called a granuloma. Less commonly, a string or batch of the small reddish bumps crop up on the exposed body area in a classic pattern called sporotrichotic lymphangitis.

It is somewhat rare to acquire this infection from well-maintained swimming pools because of protection afforded by proper chlorination. Mycobacterium marinum does not typically grow at normal body temperature. That is why it remains localized to the cooler skin surface. Overall, diagnosis and treatment of this unusual skin infection is often delayed because of a lack of suspicion for this atypical mycobacterial versus more common bacteria like Staphylococcus.

Some synonyms for Mycobacterium marinum and the resulting skin infections include tropical fish granuloma, fish tank granuloma, M. marinum, acid-fast mycobacteria, saltwater infection, freshwater infection, marine infection, marine bacteria, water-borne bacteria, and water-borne bacterial infection.