Haemophilus ducreyi
A Microbial Biorealm page on the genus Haemophilus ducreyi
Classification
Higher order taxa
Bacteria; Proteobacteria; Gammaproteobacteria; Pasteurellales; Pasteurellaceae; [Others may be used. Use NCBI link to find]
Species
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NCBI: Taxonomy |
Coccobacillus ducreyi, Bacillus ulceris cancrosi, Haemophilus ducreyi
Description and significance
Haemophilus ducreyi causes the sexually transmitted disease, Chancroid. There has been renewed interest in this bacillus because of the close connections between Chancroid and Human Immunodeficiency Virus (HIV) infections. It typically grows on the male genitalia and characteristic of a painful shallow ulcer at the site of infection. It is more common in African, Asian, and Latin American countries and is rarely seem in the US.
Haemophilus Ducreyi was first described in 1889 by Auguste Ducrey The organism was isolated on artificial media a decade later but has remained difficult to isolate consistently. However novel methods of isolating these bacteria have been developed. It can grow well on a chocolate Agar supplemented with 1% Iso VitaleX and 5% sheep blood. Oxygen and high levels of carbon dioxide are preferable, and it needs to be grown in blood clot tubes in a humid atmosphere.
Genome structure
This bacterium consists of 1,698,955 base pairs and 1717 genes. It has a circular chromosome. There are 649,349 G+C base pairs, which accounts for 38.22% of the total base pairs. Also, 1,693 open reading frames were identified in this bacterium. Only 5 plasmid profiles have been identified out of 342 strains of Haemophilus ducreyi, however the characteristics of these plasmids are still being studied.
Cell structure and metabolism
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Ecology
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Pathology
The way that H. ducreyi infects cells is that it enters the skin through wounds and stimulates keratinocytes, fibroblasts, endothelial cells, or melanocytes to secret IL-6 and IL-8. IL-8 leads to polymorphonuclear leukocytes (PMN) and macrophage accumulation in epidermis and dermis. IL-6 leads to IL-2 and IL-2 expression in T-cells. Thus this recruits CD4 to the abrasions. Fibrin and collagen deposites are part of the wound repair and act as a matrix for the PMNs and macrophages. Lipoproteins and lippligosacchride (LOS) activate macrophages to make IL-12 and TNF-α which works with chemokines. IFN- γ, which is produced by T cells, and TNF- α allow keratinocytes to make IL-8 and other chemokines which amplify the process. Inflammatory cytokines and bacterial products migrate to lymph nodes where naïve t cells to H. ducreyi antigens are sensitized. Memory T-cells specific to H. ducredyi then go to the lesion. When PMN’s and macrophages fail to clear the organism type 1 immunity is sustained and its products continue to form. The products from type 1 immunity damage the skin, this is why chancroid is a type of immunopathogenesis.
Symptoms of chancroid start with a small bump that becomes an ulcer within a day of its appearance. The ulcer ranges between 1/8 to 2 inches in size, it is painful, it has irregular or ragged borders, the base is covered with grayish or yellowish material, and it easily bleeds if traumatized. Ulcers most commonly form on the foreskin of the penis and on the groov behind the head of the penis.
Application to Biotechnology
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Current Research
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References
Edited by Anthony Nguyen, student(s) of Rachel Larsen at UCSD.
