Date of Award

8-2008

Degree Type

Dissertation

Degree Name

Doctor of Philosophy

Major

Microbiology

Major Professor

Pamela Small

Committee Members

Graham Hickling, Tim Sparer, Chunlei Su

Abstract

Mycobacterium ulcerans is the causative agent of Buruli ulcer, a necrotizing skin disease prevalent in 30 countries of West Africa and Australia. The disease begins as a painless nodule or papule that, if left untreated, can lead to ulceration that can cover much of the body. Though not usually fatal, morbidity is high, especially in rural areas where the disease is prevalent.

Epidemiological evidence has linked incidence of Buruli ulcer to slow moving or stagnant waters, but despite this, the mode of transmission is not known. Evidence for M. ulcerans in aquatic environments has relied on detection based upon PCR targeting IS2404, an insertion sequence once thought to be specific for M. ulcerans. In the past few years a growing body of evidence has shown IS2404 present in a number of aquatic mycobacterial species. Although the use of PCR primers targeting the mycolactone toxin has increased the sensitivity of M. ulcerans PCR, many ulcerans-like mycobacteria also contain the mycolactone genes. In the studies presented in this body of work we applied variable number of tandem repeat (VNTR) typing methods to environmental samples in order to map the distribution of M. ulcerans in aquatic environments in Ghana both endemic and non-endemic for Buruli ulcer. Environmental samples were collected using standardized ecological methods of sampling from 2004 until 2007. VNTR profiling was also used to genotype tissue samples of patients with Buruli ulcer in an effort to link environmental samples to human cases. Finally, the ability of M. ulcerans to associate and survive within amoeba was also tested. Results from this work demonstrate the presence of M. ulcerans in both endemic and nonendemic aquatic environments in Ghana and the association with protists. Considerable M. ulcerans heterogeneity was also found between patient and environmental samples. Results also support the use of VNTR profiling for confirmation of M. ulcerans in environmental samples, and for molecular epidemiology.

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