Francisella
You don't need to be Editor-In-Chief to add or edit content to WikiDoc. You can begin to add to or edit text on this WikiDoc page by clicking on the edit button at the top of this page. Next enter or edit the information that you would like to appear here. Once you are done editing, scroll down and click the Save page button at the bottom of the page.
| Francisella | ||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Image:Francisella tularensis 01.jpg | ||||||||||||
| Scientific classification | ||||||||||||
| ||||||||||||
| Species | ||||||||||||
Francisella is a genus of pathogenic, Gram-negative bacteria. They are small coccobacillary or rod-shaped, non-motile organisms, which are also facultative intracellular parasites of macrophages.[1] Strict aerobes, Francisella colonies bear a morphological resemblance to those of the genus Brucella.[1]
The genus was named in honor of American bacteriologist Edward Francis, who, in 1922, first recognized F. tularensis (then named Bacterium tularensis) as the causative agent of tularemia.[1]
Contents |
Pathogenesis
The type species, F. tularensis, causes the disease tularemia or rabbit fever.[1] F. novicida and F. philomiragia (previously Yersinia philomiragia) are associated with septicemia and invasive systemic infections. It should be noted that the taxonomy of the genus is somewhat uncertain, especially in the case of F. novicida (may be a subspecies of F. tularensis). In general, identification of species is accomplished by biochemical profiling or 16S rRNA sequencing.
Laboratory characteristics
Francisella can survive for several weeks in the environment; paradoxically, they can be difficult to culture and maintain in the lab.[1] Growth is slow (though increased by CO2 supplementation) and the organisms are fastidious, with most Francisella strains requiring cystine and cysteine media supplementation for growth. Growth has been successful on several media types, including chocolate agar and Thayer-Martin medias with appropriate additives as noted above. Attempted isolation on MacConkey agar is not reliable or generally successful.[1]
After 24 hours of incubation on appropriate solid media, Francisella colonies are generally small (1 to 2 mm), opaque, and white-gray to bluish-gray in color. Colonies are smooth, with clean edges and, after a 48 hours of growth, tend to have a shiny surface.
References
Web Links
- BioHealthBase Bioinformatics Resource Center The National Institute of Allergy and Infectious Disease (NIAID) supports a public database describing the molecular genetics of F. tularensis. The website describes the genes, proteins, and cellular characteristics of the pathogen.
- Francisella in Codit:Francisella tularensis
Acknowledgement and Attribution Regarding Sources of Content
Some of the initial content on this page may be incorporated in part from copyleft sources in the public domain including wikis such as Wikipedia and AskDrWiki. Drug information for patients came from the The National Library of Medicine. Infectious disease information may have come from the Centers for Disease Control (CDC). Differential Diagnoses are drawn from clinicians as well as an amalgamation of 3 sources: 1.The Disease Database; 2. Kahan, Scott, Smith, Ellen G. In A Page: Signs and Symptoms. Malden, Massachusetts: Blackwell Publishing, 2004:3; 3. Sailer, Christian, Wasner, Susanne. Differential Diagnosis Pocket. Hermosa Beach, CA: Borm Bruckmeir Publishing LLC, 2002:7 .
