Haemophilus ducreyi

Haemophilus ducreyi
{{Speciesbox
| image = Haemophilus_ducreyi_01.jpg
| image_caption = Photomicrograph of H. ducreyi
| taxon = Haemophilus ducreyi| authority = (Neveu-Lemaire, 1921)Bergey et al. 1923
}}Haemophilus ducreyi are fastidious gram-negative coccobacilli bacteria.
This species causes the sexually transmitted disease chancroid, a major cause of genital ulceration in developing countries characterized by painful sores on the genitalia. The first study linking this disease with the agent Hemophilus ducreyi was published in 1889 by Auguste Ducrey. Each year in the United States, there are over 2,000 cases of chancroid. Chancroid starts as an erythematous papular lesion that breaks down into a painful bleeding ulcer with a necrotic base and ragged edge. It has also been found to cause chronic skin ulceration away from the genitalia, infect children and adults, and behave in a manner that mimics yaws.H. ducreyi can be cultured on chocolate agar. It is best treated with a macrolide, e.g. azithromycin, and a third-generation cephalosporin, e.g. ceftriaxone.
MorphologyHaemophilus ducreyi is a Gram-negative rod-shaped bacterium. This species of bacterium has pili that allow bacteria to attach to surfaces, including those of cells.
Colonies
Colonies of Haemophilus ducreyi are described as yellow-grey, small, and semiopaque as well as nonmucoid. Scanning electron microscopy has been used to observe that the microbe can form a colony of many cells; the cells adhere to each other because of an intercellular matrix. This bond can make it difficult to isolate a single cell of Haemophilus ducreyi, hindering the genetic studies that have been done on the microbe.
Metabolism
There is very limited research on the metabolic pathways of Haemophilus ducreyi; however, it has been shown that they have high phosphatase activity (acid phosphatase, alkaline phosphatase, and phosphoamidase). There are specific temperature and nutritional necessities for the pathogen to grow, requiring advanced laboratory equipment to study the bacteria.
PathogenesisHaemophilus ducreyi is a human pathogen; there are currently no known animals or environments where the pathogen is found to live. H. ducreyi is an opportunistic microorganism that infects its host by way of breaks in the skin or epidermis. Inflammation then takes place as the area of infection is inundated with lymphocytes, macrophages, and granulocytes. This pyogenic inflammation causes regional lymphadenitis in the sexually transmitted disease chancroid.
Toxins Haemophilus ducreyi is able to defend itself against the immune response's T cells through two toxins: a hemolysin and the cytolethal distending toxin (CDT). CDT is characterized by its ability to arrest epithelial cells in the G2 phase of the cell cycle and combats T cells by inducing apoptosis.
Diagnosis
Although antigen detection, serology, and genetic amplification methods are sometimes used to diagnose infections with H. ducreyi and the genetic tests have greater sensitivity, they are not widely available, so cultures are currently considered the "gold standard" test.
Treatment
Single-dose antibiotic treatments using macrolides, third-generation cephalosporins, or fluoroquinolone continue to be effective in treating chancroid.The first line treatments are one of four options : azithromycin 1 gram orally in a single dose, ceftriaxone 250 mg intramuscularly in a single dose, ciprofloxacin 500 mg orally 2 times a day for 3 days, or erythromycin base 500 mg orally 3 times a day for 7 days. Infected individuals are still susceptible to reinfection due to the absence of developed protective immunity.
See also
Sexually transmitted disease
References
External links
Haemophilus ducreyi at the NCBI Taxonomy Browser
Type strain of Haemophilus ducreyi at BacDive'', the Bacterial Diversity Metadatabase
ducreyi
Bacteria described in 1923
Taxa named by Maurice Neveu-Lemaire