Workflow for swabs included in the statistical analysis. The complete set of M. ulcerans primary culturing inoculations was used to identify factors that affect the rate of contamination (non-contamination vs. contamination; A). A subset of the inoculations was used to identify factors that influence the growth of M. ulcerans in the absence of any contamination (M. ulcerans growth vs. no growth; B) and a second subset was used to identify factors that affect M. ulcerans growth if some of the inoculations resulted in contamination (M. ulcerans growth vs. contamination or no growth; C). The number of swabs collected as well as the transport media used and the storage time are shown. Further, the number of qPCR positive swabs with their average Ct value are given and the numbers of decontaminations as well as inoculations performed are shown. Finally the number of total inoculations in each of the data sets is indicated.