Which of the following is a characteristic of Francisella tularensis?
Tiny, pin-point, translucent colonies after 18-24 hours. Difficult to see individual colonies in growth that is less than 24 hours. Gray-white, opaque colonies less than 1 mm after 48 hours. No hemolysis.
How do you know if you have Francisella tularensis?
F. tularensis is a tiny, poorly counterstaining (by safranin) Gram- negative coccobacillus (0.2 to 0.5 µm by 0.7 to 1.0 µm). The Gram stain interpretation may be difficult because the cells are minute and faintly staining (Fig.
What is Francisella tularensis shape?
Francisella tularensis, a Gram-negative, nonspore-forming, nonmotile, aerobic rod-shaped coccobacillus, is the causative agent of tularemia.
Where is Francisella tularensis found?
A. Tularemia, also known as “rabbit fever,” is a disease caused by the bacterium Francisella tularensis. Tularemia is typically found in animals, especially rodents, rabbits, and hares.
What are the virulence factors of Francisella tularensis?
The virulence factors for F. tularensis are largely unknown, but are currently under investigation. Once F. tularensis is engulfed by immune cells (macrophages) that routinely kill bacteria, it replicates and evades parts of the immune system.
How is Francisella tularensis cultured?
Tularemia diagnosis can be established by culturing the bacteria responsible for antibody detection (ELISA), or by molecular diagnostic methods (PCR). Culture isolation is difficult due slowly grown as small colonies and require blood agar media with glucose and cysteine.
How is Francisella tularensis culture and identified?
When is it useful to repeat serologic testing for F. tularensis? Repeat testing may be useful if testing was performed early after illness onset—before detectable levels of antibodies developed. In this case, it can be useful to document seroconversion.
Is Francisella tularensis aerobic or anaerobic?
Francisella tularensis is a small, non-motile, bipolar staining Gram-negative coccobacillus. It is an obligate aerobe and grows poorly on ordinary culture media. Its growth is stimulated by the presence of cysteine in the medium.
What causes Francisella tularensis?
Tularemia is caused by the bacterium Francisella tularensis. Most cases occur from being bitten by flies or ticks carrying the bacterium or from exposure to tissue from an animal infected with the bacteria. Tularemia has been found in >100 animal species including rabbits, muskrats, squirrels and beavers.
What is Ebola an example of?
Ebola is one of several viral hemorrhagic fevers, caused by infection with a virus of the Filoviridae family, genus Ebolavirus. The fatality rates of Ebola vary depending on the strain. For example, Ebola-Zaire can have a fatality rate of up to 90 percent while Ebola-Reston has never caused a fatality in humans.
Does Francisella tularensis have a capsule?
Francisella tularensis, the Gram-negative bacterium that causes tularemia, produces a high molecular weight capsule that is immunologically distinct from Francisella lipopolysaccharide but contains the same O-antigen tetrasaccharide.
What is the meaning of virulence factor?
A virulence factor is a molecule that enhances the ability of a microorganism to cause disease beyond that intrinsic to the species background. However, the presence of virulence factors does not mean that the holder strain is pathogenic.