First Detection of Mycobacterium ulcerans DNA in Environmental Samples from South America

Abstract

The occurrences of many environmentally-persistent and zoonotic infections are driven by ecosystem changes, which in turn are underpinned by land-use modifications that alter the governance of pathogen, biodiversity and human interactions. Our current understanding of these ecological changes on disease emergence however remains limited. Buruli ulcer is an emerging human skin disease caused by the mycobacterium, Mycobacterium ulcerans, for which the exact route of infection remains unclear. It can have a devastating impact on its human host, causing extensive necrosis of the skin and underlying tissue, often leading to permanent disability. The mycobacterium is associated with tropical aquatic environments and incidences of the disease are significantly higher on floodplains and where there is an increase of human aquatic activities. Although the disease has been previously diagnosed in South America, until now the presence of M. ulcerans DNA in the wild has only been identified in Australia where there have been significant outbreaks and in western and central regions of Africa where the disease is persistent. Here for the first time, we have identified the presence of the aetiological agent's DNA in environmental samples from South America. The DNA was positively identified using Real-time Polymerase Chain Reaction (PCR) on 163 environmental samples, taken from 23 freshwater bodies in French Guiana (Southern America), using primers for both IS2404 and for the ketoreductase-B domain of the M. ulcerans mycolactone polyketide synthase genes (KR). Five samples out of 163 were positive for both primers from three different water bodies. A further nine sites had low levels of IS2404 close to a standard CT of 35 and could potentially harbour M. ulcerans. The majority of our positive samples (8/14) came from filtered water. These results also reveal the Sinnamary River as a potential source of infection to humans.

Deforestation-driven food-web collapse linked to emerging tropical infectious disease, Mycobacterium ulcerans

“…The rest of the country is predominantly pristine primary tropical rain forest including 33,900 km 2 of the Guiana Amazonian National Park and a wealth of important ecosystems ranging from marshland to coastal mangroves. Since 1969, the number of Buruli ulcer cases has remained steady but unusually high in comparison to that of other countries in the surrounding region ( 25 , 29 ). The disease is endemic in close to 30 tropical and subtropical countries, where it can affect health and lead to serious socioeconomic consequences ( 30 ).…”

“…( 26 ) and Morris et al . ( 29 )]. The number of bacilli in the sample was estimated from the PCR data of KR because it is more specific to M. ulcerans .…”

Epidemiology and disease burden of Buruli ulcer: a review

“…Published reports on the occurrence of M. ulcerans infections are limited [41][42][43][44]47,48 and only very few cases of BU have been reported to the WHO. While fewer than ten cases per country have been confirmed in Suriname, Mexico, Peru, and Brazil in the past 50 years, 42 .250 cases have been notified between 1969 and 2014 in French Guiana, which borders Brazil to the east and south, and Suriname to the west.…”

“…Considering the small population, the number of infections is relatively high with an average annual incidence of .2/100,000. 43 Construction of the Petit-Saut Dam in 1994 upstream the BU endemic area has been associated with a significant decline in case numbers, possibly by a better regulation of water flows. Recently, M. ulcerans DNA (IS2404 and the ketoreductase B domain gene) has been detected in specimens from three of 23 different freshwater bodies sampled in French Guiana, indicative for the presence of this species in the environment.…”

“…Recently, M. ulcerans DNA (IS2404 and the ketoreductase B domain gene) has been detected in specimens from three of 23 different freshwater bodies sampled in French Guiana, indicative for the presence of this species in the environment. 43 The recent observation of genetic heterogeneity among 23 isolates from patients living along the coastline of French Guiana as revealed by Multilocus Variable Number Tandem Repeat Analysis 44 is uncommon for M. ulcerans, which usually shows very limited genetic diversity within particular endemic areas. 14,45,46 While two of the genotypes detected in French Guiana showed high similarity, one had distinctly different characteristics and shared more sequence similarity with the M. ulcerans ecovar liflandii.…”