Date of Award


Document Type


Degree Name

Master of Science (MS)



First Advisor

White, Catherine D. Dr.


Haemophilus ducreyi is a Gram negative, strict human pathogen that causes the genital ulcer disease chancroid. Chancroid is a sexually transmitted infection that may aid in transmission of the Human Immunodeficiency Virus. Haemophilus ducreyi can be categorized into two strain classes, class I (CI) and class II (CII), based on variations in DNA sequence and protein expression of several virulence determinants including Ducreyi Serum Resistance protein A (DsrA) and the Necessary for Collagen Adhesion protein (NcaA). Recently, the first description of non-sexually associated chancroid transmission in children with chronic lower limb ulcerations was reported. Bacteria isolated from the children were sequenced and determined to possess a 16 S rDNA sequence that was 100% identical to Haemophilus ducreyi CII strain 33921. The purpose of this study was to categorize four strains of Haemophilus ducreyi isolated from children in Samoa as CI or CII based on DsrA and NcaA nucleotide and amino acid sequence. Based on the presence of a 16S rDNA that was 100% identical to CII strain 33921, we hypothesized that these strains were CII. To examine DsrA and NcaA, strains SB 5755, SB 5756, SB 5757, and BE 3135 were subjected to Polymerase Chain Reaction and DNA sequencing. SB 5755, SB 5756, and BE 3145 was 90%, 96% and 97% identical to dsrA in the CI parent strain 35000 HP, respectively. Moreover, alignment of DsrA the xii predicted protein sequences demonstrated that SB 5755, SB 5756, and BE3145 were 71%, 87%, and 92% identical to 35000 HP. However, comparison with HMC112 dsrAII revealed a high degree of variability between the N-terminal regions. SB 5755 had 7% identites and 17% similarities, SB 5756 had 7% identites and 21% similarites, and BE 3145 had 5% identies and 17% similarites to dsrAII These data indicate that SB 5755, SB 5756, and BE 3145 are not CII, but are indeed CI strains.