title: Spatial Distribution of Mycobacterium ulcerans in Buruli Ulcer Lesions: Implications for Laboratory Diagnosis.
abstract: 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.
  
  
  
  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.
  
  
  
  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.
authors.affiliation: Swiss Tropical and Public Health Institute, Basel, Switzerland.|University of Basel, Basel, Switzerland.
authors.forename: Marie-Thérèse
authors.initials: MT
authors.lastname: Ruf
authors.affiliation: Swiss Tropical and Public Health Institute, Basel, Switzerland.|University of Basel, Basel, Switzerland.
authors.forename: Miriam
authors.initials: M
authors.lastname: Bolz
authors.affiliation: Section Clinical Tropical Medicine, Heidelberg University Hospital, Heidelberg, Germany.
authors.forename: Moritz
authors.initials: M
authors.lastname: Vogel
authors.affiliation: Fairmed, Bureau Régional pour l'Afrique, B.P. 5807, Yaoundé, Cameroon.
authors.forename: Pierre F
authors.initials: PF
authors.lastname: Bayi
authors.affiliation: Swiss Tropical and Public Health Institute, Basel, Switzerland.|University of Basel, Basel, Switzerland.
authors.forename: Martin W
authors.initials: MW
authors.lastname: Bratschi
authors.affiliation: Centre de Depistage et de Traitement de l'Ulcere de Buruli d'Allada, Allada, Benin.
authors.forename: Ghislain Emmanuel
authors.initials: GE
authors.lastname: Sopho
authors.affiliation: Noguchi Memorial Institute for Medical Research, University of Ghana, Legon, Ghana.
authors.forename: Dorothy
authors.initials: D
authors.lastname: Yeboah-Manu
authors.affiliation: Fairmed, Bureau Régional pour l'Afrique, B.P. 5807, Yaoundé, Cameroon.
authors.forename: Alphonse
authors.initials: A
authors.lastname: Um Boock
authors.affiliation: Section Clinical Tropical Medicine, Heidelberg University Hospital, Heidelberg, Germany.
authors.forename: Thomas
authors.initials: T
authors.lastname: Junghanss
authors.affiliation: Swiss Tropical and Public Health Institute, Basel, Switzerland.|University of Basel, Basel, Switzerland.
authors.forename: Gerd
authors.initials: G
authors.lastname: Pluschke
mesh_terms: D054312:Buruli Ulcer / Q000382:microbiology* / Q000473:pathology*; D004269:DNA, Bacterial / Q000302:isolation & purification*; D006801:Humans; D019911:Mycobacterium ulcerans / Q000302:isolation & purification*; D012867:Skin / Q000382:microbiology; D012883:Skin Ulcer / Q000382:microbiology*
chemical_list: D004269:DNA, Bacterial