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Diagnosis
Experienced observers can often make accurate clinical diagnoses of BU. Laboratory diagnosis includes identification of AFB in exudates taken by swabs from the undermined edges of ulcers. The same material can be used for PCR analysis of M. ulcerans-specific sequences, and for culture on Löwenstein-Jensen medium incubated at 32°C. Similar microbiologic studies can be performed on fresh unfixed biopsy specimens. If microbiologic studies cannot be performed locally, the swabs or biopsy specimens can be placed in transport medium and sent to a specialty laboratory. Specimens for histopathologic diagnosis should be taken from the edge of ulcers and should include subcutaneous tissue and fascia. Biopsy specimens from nonulcerated lesions should come from the presumed center. AFB are best seen in Ziehl-Neelsen-stained sections. Tissue ellipses are more frequently diagnostic than punch specimens. The photomicrograph (left, Ziehl-Neelsen stain) demonstrates extracellular AFB, single and in clusters, in smear of exudates of undermined area of a Buruli ulcer.
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