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Spatial distribution of Mycobacterium ulcerans in Buruli ulcer lesions: implications for laboratory diagnosis

Ruf, Marie-Thérèse and Bolz, Miriam and Vogel, Moritz and Bayi, Pierre F. and Bratschi, Martin W. and Sopho, Ghislain Emmanuel and Yeboah-Manu, Dorothy and Um Boock, Alphonse and Junghanss, Thomas and Pluschke, Gerd. (2016) Spatial distribution of Mycobacterium ulcerans in Buruli ulcer lesions: implications for laboratory diagnosis. PLoS Neglected Tropical Diseases, 10 (6). e0004767.

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Abstract

BACKGROUND: Current laboratory diagnosis of Buruli ulcer (BU) is based on microscopic detection of acid fast bacilli, quantitative real-time PCR (qPCR), histopathology or cultivation. Insertion sequence (IS) 2404 qPCR, the most sensitive method, is usually only available at reference laboratories. The only currently available point-of-care test, microscopic detection of acid fast bacilli (AFB), has limited sensitivity and specificity.
METHODOLOGY/ PRINCIPAL FINDINGS: Here we analyzed AFB positive tissue samples (n = 83) for the presence, distribution and amount of AFB. AFB were nearly exclusively present in the subcutis with large extracellular clusters being most frequently (67%) found in plaque lesions. In ulcerative lesions small clusters and dispersed AFB were more common. Beside this, 151 swab samples from 37 BU patients were analyzed by IS2404 qPCR and ZN staining in parallel. The amount of M. ulcerans DNA in extracts from swabs correlated well with the probability of finding AFB in direct smear microscopy, with 56.1% of the samples being positive in both methods and 43.9% being positive only in qPCR. By analyzing three swabs per patient instead of one, the probability to have at least one positive swab increased from 80.2% to 97.1% for qPCR and from 45% to 66.1% for AFB smear examination.
CONCLUSION / SIGNIFICANCE: Our data show that M. ulcerans bacteria are primarily located in the subcutis of BU lesions, making the retrieval of the deep subcutis mandatory for examination of tissue samples for AFB. When laboratory diagnosis is based on the recommended less invasive collection of swab samples, analysis of three swabs from different areas of ulcerative lesions instead of one increases the sensitivity of both qPCR and of smear microscopy substantially.
Faculties and Departments:09 Associated Institutions > Swiss Tropical and Public Health Institute (Swiss TPH)
09 Associated Institutions > Swiss Tropical and Public Health Institute (Swiss TPH) > Department of Medical Parasitology and Infection Biology > Molecular Immunology (Pluschke)
UniBasel Contributors:Ruf, Marie-Thérèse and Bratschi, Martin and Bolz, Miriam and Pluschke, Gerd
Item Type:Article, refereed
Article Subtype:Research Article
Publisher:Public Library of Science
ISSN:1935-2727
e-ISSN:1935-2735
Note:Publication type according to Uni Basel Research Database: Journal article
Language:English
Identification Number:
Last Modified:21 Oct 2016 16:18
Deposited On:26 Jul 2016 13:08

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