Date of Award

2012

Document Type

Thesis

Degree Name

Master of Science (MS)

Department

Biology

First Advisor

White, Catherine D. Dr.

Abstract

Haemophilus ducreyi is a gram negative, sexually transmitted bacterial pathogen. This strict human pathogen causes the genital ulcer disease chancroid, which results in the formation of deep, painful ulcers. Chancroid infection has also been associated with high transmission rates of the Human Immunodeficiency Virus. H. ducreyi virulence has been attributed, in part, to the extracellular virulence factors large supernatant protein A (LspA) and large supernatant protein B (LspB). Recently, H. ducreyi strains were assigned to two classes, Class I (CI) and Class II (CII). Strains were grouped based on common DNA sequences, expression of several known virulence factors, and differences in lipooligosaccharide production. In 2007, four novel strains of H. ducreyi, BE3145, SB5755, SB5756, SB5757, were detected on the lower limbs of children visiting the island chain of Samoa. In this study, we examined lspA and lspB in these strains to determine whether the DNA sequences were more similar to those found in CI or CII strains. We hypothesized that the novel strains would contain lspA and lspB DNA sequences identical to those in CI strains. Therefore, Polymerase Chain Reaction was used to amplify lspA and lspB, and the PCR products were sequenced and compared to the CI parent strain, 35000HP and CII parent strain, HMC112. Both lspA and lspB were detected in all four novel strains. In addition, lspA was amplified in HMC112; while lspB could not be amplified in this strain. It was determined that SB5755, SB5757, and BE3145 contained lspA that were 100% identical to 35000HP, while SB5756 possessed 99% identity. However, none of the lspA sequences were similar to HMC112. SB5755 and SB5756 contained lspB that were 100% identical to 35000HP, while SB5757 lspB was 99% identical to 35000HP. Interestingly, BE3415 showed very little identity to 35000HP. Based on these data, strains BE3145, SB5755, SB5756, SB5757 are more similar to CI strains.

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