Rheumatoid

Rheumatoid

Mycobacterium marinum – Diagnosis

Diagnosis is frequently delayed, probably due to the rarity of the infection and a failure to elicit the usual history of aquatic exposure. Common misdiagnoses include fungal and parasitic infection, cellulitis, skin tuberculosis, rheumatoid arthritis, foreign body reaction, and skin tumor.

Diagnosis is frequently delayed, probably due to the rarity of the infection and a failure to elicit the usual history of aquatic exposure. Common misdiagnoses include fungal and parasitic infection, cellulitis, skin tuberculosis, rheumatoid arthritis, foreign body reaction, and skin tumor. A high index of suspicion and a detailed history are important in establishing the diagnosis of ''M. marinum'' infection. Long delays in diagnosis can result in severe, destructive infection. On primary isolation ''M. marinum'' grows on LJ slants at 30-33°C in 7-21 days. Unlike M. tuberculosis, most strains of ''M. marinum'' will not grow at the usual incubation temperature of 37°C. Colonies are cream in color and turn yellow when exposed to light (photochromogenic). ''M. marinum'', once cultured, is readily identified by using conventional mycobacterial characterization methods. It grows relatively quickly (1 to 2 weeks) and is easily recognized as a result of its photochromogenicity. Infections due to ''M. marinum'' can usually be treated with antimycobacterial drugs. Sometimes, cultures are negative but the diagnosis is still made based on physical signs supported by typical histological findings, as ''M. marinum'' is a very common atypical mycobacterium causing skin infection (70). Various DNA-based techniques have been used to classify mycobacteria. All such studies have demonstrated a high taxonomic affiliation between M. ulcerans and ''M. marinum''. Some ''M. marinum'' isolates have been shown to harbor the insertion sequence, IS''2404'', however, no ''M. marinum'' strains contain IS''2606''. ''M. ulcerans'' isolates are positive for both insertion sequences. It was previously thought that IS''2404'' and IS''2606'' were specific to ''M. ulcerans'' but recent evidence has proved this true only for IS''2606''.

The management of ''M. marinum'' infections depends on the severity of the infection. A prolonged course of antibiotic therapy is curative in most superficial cases but adjunctive surgical intervention is sometimes indicated in extensive and deep infections.

Adapted from the Wikipedia article Mycobacterium marinum, under the G. N. U. Free Documentation License. Please also see http://en.wikipedia.org/wiki