Mycobacterium ulcerans DNA Not Detected in Faecal Samples from Buruli Ulcer Patients: Results of a Pilot Study

It has recently been shown that in a Buruli ulcer (BU) endemic region of southeastern Australia, significant numbers of possums (native tree-dwelling marsupials) have clinical BU disease. Furthermore, based on quantitative PCR (qPCR) analysis, animals with BU lesions (and some without) shed M. ulcerans DNA in their faeces, indicative of bacterial loads of up to 108 organisms/gram. These findings led us to propose that humans might also harbour M. ulcerans in their gastrointestinal tract and shed the bacterium in their faeces. We conducted a pilot study and collected faecal swabs from 26 patients with confirmed BU and 31 healthy household controls. Faecal samples were also collected from 10 healthy controls from non-endemic regions in Ghana. All 67 specimens were negative when tested by IS2404 PCR. The detection sensitivity of this method was ≥104 bacteria per gram (wet-weight) of human faecal material. We conclude that the human gastrointestinal tract is unlikely to be a significant reservoir of M. ulcerans

Climate and Landscape Factors Associated with Buruli Ulcer Incidence in Victoria, Australia

Background Buruli ulcer (BU), caused by Mycobacterium ulcerans (M. ulcerans), is a necrotizing skin disease found in more than 30 countries worldwide. BU incidence is highest in West Africa; however, cases have substantially increased in coastal regions of southern Australia over the past 30 years. Although the mode of transmission remains uncertain, the spatial pattern of BU emergence in recent years seems to suggest that there is an environmental niche for M. ulcerans and BU prevalence. Methodology/Principal Findings Network analysis was applied to BU cases in Victoria, Australia, from 1981–2008. Results revealed a non-random spatio-temporal pattern at the regional scale as well as a stable and efficient BU disease network, indicating that deterministic factors influence the occurrence of this disease. Monthly BU incidence reported by locality was analyzed with landscape and climate data using a multilevel Poisson regression approach. The results suggest the highest BU risk areas occur at low elevations with forested land cover, similar to previous studies of BU risk in West Africa. Additionally, climate conditions as far as 1.5 years in advance appear to impact disease incidence. Warmer and wetter conditions 18–19 months prior to case emergence, followed by a dry period approximately 5 months prior to case emergence seem to favor the occurrence of BU. Conclusions/Significance The BU network structure in Victoria, Australia, suggests external environmental factors favor M. ulcerans transmission and, therefore, BU incidence. A unique combination of environmental conditions, including land cover type, temperature and a wet-dry sequence, may produce habitat characteristics that support M. ulcerans transmission and BU prevalence. These findings imply that future BU research efforts on transmission mechanisms should focus on potential vectors/reservoirs found in those environmental niches. Further, this study is the first to quantitatively estimate environmental lag times associated with BU outbreaks, providing insights for future transmission investigations.This project was supported by the World Health Organization and the National Institutes of Health and Fogarty International Center (NIH - R01TW007550). The content is solely the responsibility of the authors and does not necessarily represent the official views of the Fogarty International Center or the National Institutes of Health. R.W. Merritt is gratefully acknowledged for supporting this research as part of NIH grant R01TW007550

Risk of Buruli Ulcer and Detection of Mycobacterium ulcerans in Mosquitoes in Southeastern Australia

Buruli ulcer (BU) is a destructive skin condition caused by infection with the environmental bacterium, Mycobacterium ulcerans. BU has been reported in more than 30 countries in Africa, the Americas, Asia and the Western Pacific. How people become infected with M. ulcerans is not completely understood, but numerous studies have explored the role of biting insects. In 2007, it was discovered that M. ulcerans could be detected in association with mosquitoes trapped in one town in southeastern Australia during a large outbreak of BU. In the present study we investigated whether there was a relationship between the incidence of BU in humans in several towns and the likelihood of detecting M. ulcerans in mosquitoes trapped in those locations. We found a strong association between the proportion of M. ulcerans-positive mosquitoes and the incidence of human disease. The results of this study strengthen the hypothesis that mosquitoes are involved in the transmission of M. ulcerans in southeastern Australia. This has implications for the development of strategies to control and prevent BU

Sero-Epidemiology as a Tool to Screen Populations for Exposure to Mycobacterium ulcerans

Sero-epidemiological analyses revealed that a higher proportion of sera from individuals living in the Buruli ulcer (BU) endemic Densu River Valley of Ghana contain Mycobacterium ulcerans 18 kDa small heat shock protein (shsp)-specific IgG than sera from inhabitants of the Volta Region, which was regarded so far as BU non-endemic. However, follow-up studies in the Volta Region showed that the individual with the highest anti-18 kDa shsp-specific serum IgG titer of all participants from the Volta Region had a BU lesion. Identification of more BU patients in the Volta Region by subsequent active case search demonstrated that sero-epidemiology can help identify low endemicity areas. Endemic and non-endemic communities along the Densu River Valley differed neither in sero-prevalence nor in positivity of environmental samples in PCR targeting M. ulcerans genomic and plasmid DNA sequences. A lower risk of developing M. ulcerans disease in the non-endemic communities may either be related to host factors or a lower virulence of local M. ulcerans strains

Mycobacterium tuberculosis lineage 4 comprises globally distributed and geographically restricted sublineages

Generalist and specialist species differ in the breadth of their ecological niches. Little is known about the niche width of obligate human pathogens. Here we analyzed a global collection of Mycobacterium tuberculosis lineage 4 clinical isolates, the most geographically widespread cause of human tuberculosis. We show that lineage 4 comprises globally distributed and geographically restricted sublineages, suggesting a distinction between generalists and specialists. Population genomic analyses showed that, whereas the majority of human T cell epitopes were conserved in all sublineages, the proportion of variable epitopes was higher in generalists. Our data further support a European origin for the most common generalist sublineage. Hence, the global success of lineage 4 reflects distinct strategies adopted by different sublineages and the influence of human migration.We thank S. Lecher, S. Li and J. Zallet for technical support. Calculations were performed at the sciCORE scientific computing core facility at the University of Basel. This work was supported by the Swiss National Science Foundation (grants 310030_166687 (S.G.) and 320030_153442 (M.E.) and Swiss HIV Cohort Study grant 740 to L.F.), the European Research Council (309540-EVODRTB to S.G.), TB-PAN-NET (FP7-223681 to S.N.), PathoNgenTrace projects (FP7-278864-2 to S.N.), SystemsX.ch (S.G.), the German Center for Infection Research (DZIF; S.N.), the Novartis Foundation (S.G.), the Natural Science Foundation of China (91631301 to Q.G.), and the National Institute of Allergy and Infectious Diseases (5U01-AI069924-05) of the US National Institutes of Health (M.E.)