News Article
August 10, 2010
Newly-identified Human Pathogen is Cause of Disease in sub-Saharan Africa
A new form of bacteria has been found to cause disease among HIV-infected individuals in sub-Saharan Africa. Termed Mycobacterium sherrisii, the organism has been officially recognized as a new species by a team of scientists, including Duke infectious diseases scientist and DGHI member John Crump and DGHI partners at the Kilimanjaro Christian Medical Centre (KCMC).
In a recently published paper in the International Journal of Systematic and Evolutionary Microbiology, researchers identified the characteristics of M. sherrisii after they tested for similarities and differences in chemical composition and physiological properties in 11 closely-related strains of bacteria. The molecular testing was conducted in Italy and the Netherlands after Crump and Anne Morrissey, former KCMC Biotechnology Laboratory supervisor, discovered that several HIV-infected patients suffered from an unusual type of bacterial bloodstream infection.
In sub-Saharan Africa, most mycobacterial bloodstream infections are due to Mycobacterium tuberculosis, the cause of tuberculosis. However, during his research Crump and his team noticed the atypical isolates found in certain patients did not resemble that organism, nor did they resemble several other common species found in higher-income countries.
With further testing and analysis of the Moshi bacteria samples at the Dutch National Mycobacteria Reference Laboratory, the group confirmed that M. sherrisii is the second leading cause of mycobacterial bloodstream infection in Moshi, Tanzania, following M. tuberculosis. The bacteria was first named by microbiologists at the University of Washington in 2004, but its existence in Africa was unknown. This paper officially recognizes M. sherrisii as a new species that causes human disease. As a result, HIV-infected patients in Moshi with M. sherrisii will receive more appropriate diagnosis and therapy.
“The combination of a strong microbiology section at the KCMC Biotechnology Laboratory and excellent collaborators allowed us to demonstrate that M. sherrisii is an important cause of disease in HIV-infected persons in Moshi,” said Crump, which is significant because most microbiology laboratories in sub-Saharan Africa do not have the capacity, and focus their resources only on the diagnosis of tuberculosis. “Being involved in the official recognition of M. sherrisii as a new bacterial species, particularly one that is associated with significant disease in Africa, is exciting and is probably a once in a lifetime experience.”
Crump and his team speculate M. sherrisii is likely associated with the immunosuppression of advanced HIV, but further work is needed to describe the organism’s epidemiology in sub-Saharan Africa, and to identify its source in the environment.
“This organism was previously not known to be an important cause of disseminated disease in persons with HIV infection in sub-Saharan Africa, and the work represents a unique observation,” said DGHI Associate Director of Research John Bartlett, principal investigator of an International Studies of AIDS-associated Co-infection (ISAAC) grant, which funded the study. “The award to Duke and KCMC allowed us to do very careful studies of infections complicating AIDS in Tanzania.”
Collaborating institutions on this paper include the Dutch National Mycobacteria Reference Laboratory, the Duke-KCMC collaboration, the Regional Reference Centre for Mycobacteria in Florence, Italy, and the Department of Microbiology at the University of Washington. Authors of the paper include Jakko van Ingen, Enrico Tortoli, Rangaraj Selvarangan, Marie B. Coyle, John Criump, Anne Morrissey, P.N. Richard Dekhuijzen, and Martin J. Boeree and Dick van Soolingen.
KCMC is one of DGHI’s longest-running collaborations in research, education and service. Learn more about DGHI’s research, education and service initiatives in Moshi, Tanzania.