Northside Health Library

Swimming pool granuloma


A swimming pool granuloma is a long-term (chronic) skin infection caused by the bacteria Mycobacterium marinum.

Alternative Names

Aquarium granuloma; Fish tank granuloma


A swimming pool granuloma occurs when water containing Mycobacterium marinum bacteria enters a break in the skin. Signs of a skin infection appear about 2 - 3 weeks later.

Risks include exposure to swimming pools, salt water aquariums, or ocean fish.


The main symptom is a reddish bump (papule) that slowly grows into a purplish nodule.

The elbows, fingers, and back of the hands are the most common body parts affected. The knees and legs are less commonly affected.

The nodules may break down and leave an open sore. Sometimes, they may spread up the limb, but most often they stay a simple skin sore.

Exams and Tests

Tests to diagnose swimming pool granuloma include:


Antibiotics are used to treat this infection. They are chosen based on the results of the culture and skin biopsy.

You may need several months of treatment with a combination of antibiotics. Surgery may also be needed.

Outlook (Prognosis)

Swimming pool granulomas can usually be cured with antibiotics. However, you may have scarring.

Possible Complications

Occasionally, joint or bone infections occur. The disease may be longer or more complicated in patients whose immune system is not working properly.

When to Contact a Medical Professional

Call your health care provider if you develop reddish bumps on your skin which do not clear with home treatment.


Avoid contact with contaminated water. Wear gloves or wash thoroughly when cleaning aquariums.


Brown-Elliott BA, Wallace RJ Jr. Infections due to nontuberculous mycobacteria other than Mycobacterium avium-intracellulare. In: Mandell GL, Bennett JE, Dolin R, eds. Principles and Practice of Infectious Disease. 7th ed. Philadelphia, Pa: Saunders Elsevier; 2009:chap 253.

Holland S. The nontuberculous mycobacteria. In: Goldman L, Ausiello D, eds. Cecil Medicine. 23rd ed. Philadelphia, Pa: Saunders Elsevier; 2007:chap 346.

Review Date: 2/5/2011
Reviewed By: David C. Dugdale, III, MD, Professor of Medicine, Division of General Medicine, Department of Medicine, University of Washington School of Medicine. Review provided by VeriMed Healthcare Network. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.
The information provided herein should not be used during any medical emergency or for the diagnosis or treatment of any medical condition. A licensed medical professional should be consulted for diagnosis and treatment of any and all medical conditions. Call 911 for all medical emergencies. Links to other sites are provided for information only -- they do not constitute endorsements of those other sites. © 1997- A.D.A.M., Inc. Any duplication or distribution of the information contained herein is strictly prohibited.

Northside Hospital - Atlanta

1000 Johnson Ferry Road NE
Atlanta, GA 30342
(404) 851-8000

Northside Hospital - Cherokee

201 Hospital Road
Canton, GA 30114
(770) 720-5100

Northside Hospital - Forsyth

1200 Northside Forsyth Drive
Cumming, GA 30041
(770) 844-3200

Copyright © 2015 Northside Hospital|Privacy Policy