Mycobacterium Marinum (cont.)

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What tests are available to diagnose the infection?

Lab tests include cultures where a swab or sample is taken and grown in the laboratory. Cultures of M. marinum are fairly difficult to grow and usually may take several weeks in the lab. The culture may be negative, even if there is an active infection. Treatment may still be considered even if the test results are negative, especially if the patient's history supports past fish or fish-tank exposure.

In the absence of positive culture results, a skin or tissue biopsy may be a helpful test for diagnosis. This may help find the microscopic bacteria.

A special test called polymerase chain reaction (PCR) of tissue may be used in difficult cases to assist in naming the exact type of bacteria or Mycobacterium species involved.

How is Mycobacterium marinum infection treated?

Most infections are treated medically with a fairly long course of oral antibiotics. Medications may be required anywhere from three to six months or more depending on the severity of the disease and spread of the infection. Typically, physicians may recommend continuing the medications for an additional four to six weeks even after all of the symptoms have fully cleared.

The gold standard for treatment of infection by M. marinum is oral antibiotics. Clarithromycin is currently the preferred antibiotic selection. Other antibiotic options include rifampin plus ethambutol, tetracyclines, trimethoprim-sulfamethoxazole, and fluoroquinolones.

Some milder infections (mainly in healthy people) have cleared on their own without any treatment. Rarely, surgical treatment and drainage of deeper tissue or skin infections may become necessary in more complicated cases. However, medical treatment remains the primary and preferred treatment for nearly all cases.

Medically Reviewed by a Doctor on 12/12/2013

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