Source: Public Library of Science

An international team of 17 researchers from four countries has for the first time isolated from the environment and fully characterised the organism that causes Buruli ulcer.

The study, published in the March 26 issue of PLoS Neglected Tropical Diseases, lends support to the idea that the organism, Mycobacterium ulcerans, is transmitted to humans from environmental aquatic niches, rather than from person to person.

Buruli ulcer is a neglected, devastating, necrotising disease, sometimes producing massive, disfiguring ulcers, with huge social impact.

The disease occurs predominantly in impoverished, humid, tropical, rural areas of Africa, where the incidence has been increasing, surpassing tuberculosis and leprosy (two other diseases caused by mycobacteria) in some regions.

The bacteria are found in 40 other countries, including Australia, but the disease is predominantly one of the poor.

Although it has long been believed that Mycobacterium ulcerans is an environmental pathogen transmitted to humans from its aquatic niches, until now the organism has not been isolated in pure culture from environmental sources.

Francoise Portaels of the Institute of Tropical Medicine in Antwerp, Belgium, and colleagues in Ghana, Portugal, and the US, now present details of the isolation and characterisation of a M. ulcerans strain from the environment. To the best of their knowledge, this is the first time that the organism has ever been isolated and fully characterised from the environment.

The isolated strain has microbiological features typical of African strains of M. ulcerans and was isolated from an aquatic insect (the Water Strider) from a Buruli ulcer-endemic area in Benin, West Africa.

"Our findings support the concept that Mycobacterium ulcerans is a pathogen of humans with an aquatic environmental niche, and will have positive consequences for the control of this neglected and socially important tropical disease," the authors write.

In a related expert commentary, Tim Stinear of Monash University and Paul Johnson of the Austin Hospital, who were not involved in the study, say that the new study is "a major achievement and will serve as the definitive reference point for scientists' intent on revealing the ecology, environmental reservoir, and precise mode of transmission of Mycobacterium ulcerans."