Francisella: Difference between revisions
No edit summary |
|||
Line 27: | Line 27: | ||
===Causative Agent=== | ===Causative Agent=== | ||
*The type species, ''[[Francisella tularensis|F. tularensis]]'', causes the disease [[tularemia]] or rabbit fever.<ref name="Baron">{{cite book | author = Collins FM | title = Pasteurella, Yersinia, and Francisella. ''In:'' Baron's Medical Microbiology ''(Baron S ''et al'', eds.)| edition = 4th ed. | publisher = Univ of Texas Medical Branch | year = 1996 | url = http://www.ncbi.nlm.nih.gov/books/bv.fcgi?rid=mmed.section.1624 | id = ISBN 0-9631172-1-1 }}</ref> ''[[Francisella novicida|F. novicida]]'' and ''[[Francisella philomiragia|F. philomiragia]]'' (previously ''Yersinia philomiragia'') are associated with [[septicemia]] and invasive systemic infections. | *The type species, ''[[Francisella tularensis|F. tularensis]]'', causes the disease [[tularemia]] or rabbit fever.<ref name="Baron">{{cite book | author = Collins FM | title = Pasteurella, Yersinia, and Francisella. ''In:'' Baron's Medical Microbiology ''(Baron S ''et al'', eds.)| edition = 4th ed. | publisher = Univ of Texas Medical Branch | year = 1996 | url = http://www.ncbi.nlm.nih.gov/books/bv.fcgi?rid=mmed.section.1624 | id = ISBN 0-9631172-1-1 }}</ref> ''[[Francisella novicida|F. novicida]]'' and ''[[Francisella philomiragia|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. | *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 assays|biochemical]] profiling or 16S [[rRNA]] sequencing. | ||
*F. tularensis is found in widely diverse animal hosts and habitats and can be recovered from contaminated water, soil, and vegetation. | *F. tularensis is found in widely diverse [[Host (biology)|animal hosts]] and habitats and can be recovered from contaminated water, soil, and vegetation. | ||
*A variety of small mammals, including voles, mice, water rats, squirrels, rabbits, and hares are natural reservoirs of infection. | *A variety of small mammals, including voles, mice, water rats, squirrels, rabbits, and hares are natural reservoirs of infection. | ||
*They acquire infection through [[tick]], fly, and mosquito bites and by contact with contaminated environments. | *They acquire infection through [[tick]], fly, and mosquito bites and by contact with contaminated environments. | ||
*Epizootics with sometimes extensive die-offs of animal hosts may herald outbreaks of tularemia in humans. | *[[Epizootic|Epizootics]] with sometimes extensive die-offs of animal hosts may herald [[Outbreak|outbreaks]] of tularemia in humans. | ||
*Humans can become incidentally infected through diverse environmental exposures: bites by infected arthropods; handling infectious animal tissues or fluids; direct contact with or ingestion of contaminated food, water, or soil; and inhalation of infective aerosols. | *Humans can become incidentally infected through diverse environmental exposures: bites by infected [[Arthropod|arthropods]]; handling infectious [[Tissue|animal tissues]] or fluids; direct contact with or ingestion of contaminated food, water, or soil; and inhalation of infective aerosols. | ||
*Humans can develop severe and sometimes fatal illness, but do not transmit the disease to others. | *Humans can develop severe and sometimes [[fatal]] illness, but do not transmit the disease to others. | ||
===Genomics=== | ===Genomics=== | ||
*Studies conducted on a strain of the Schu S4 genome report a genome size of less than 2 Mbp. | *Studies conducted on a strain of the Schu S4 [[genome]] report a [[genome]] size of less than 2 Mbp. | ||
*F. tularensis is composed of a large majority of genes, unique to the species. | *F. tularensis is composed of a large majority of [[genes]], unique to the species. | ||
*Lesser amount of genes responsible for the encoding of transport and binding. | *Lesser amount of genes responsible for the [[Encoding (memory)|encoding]] of transport and binding. | ||
*There are few matches for genes responsible for gene regulation and energy metabolism between F. tularensis and other documented | *There are few matches for genes responsible for [[gene regulation]] and energy [[metabolism]] between F. tularensis and other documented | ||
== Pathogenesis == | == Pathogenesis == | ||
===Mechanism of infection=== | ===Mechanism of infection=== | ||
* ''[[Francisella|Francisella tularensis]]'' is one of the most | * ''[[Francisella|Francisella tularensis]]'' is one of the most [[Infectious Disease|infectious]] bacteria known; fewer than ten organisms can cause disease leading to severe illness. | ||
* The bacteria penetrate into the body through damaged skin and mucous membranes, or through inhalation. | * The bacteria penetrate into the body through damaged skin and [[mucous membranes]], or through inhalation. | ||
* Humans are most often infected by tick bite or through handling an infected animal. Ingesting infected water, soil, or food can also cause infection. | * Humans are most often infected by tick bite or through handling an infected animal. Ingesting infected water, soil, or food can also cause infection. | ||
* Tularemia can also be acquired by inhalation; hunters are at a higher risk for this disease because of the potential of inhaling the bacteria during the skinning process. | * Tularemia can also be acquired by [[inhalation]]; hunters are at a higher risk for this disease because of the potential of inhaling the bacteria during the skinning process. | ||
* Tularemia is not spread directly from person to person. | * Tularemia is not spread directly from person to person. | ||
* ''Francisella tularensis'' is an intracellular bacterium, meaning that it is able to live as a parasite within host cells. | * ''Francisella tularensis'' is an [[intracellular]] bacterium, meaning that it is able to live as a [[Parasites|parasite]] within [[Host (biology)|host]] cells. | ||
* It primarily infects [[macrophages]], a type of white blood cell. It is thus able to evade the immune system. | * It primarily infects [[macrophages]], a type of white blood cell. It is thus able to evade the immune system. | ||
* The course of disease involves spread of the organism to multiple organ systems, including the lungs, liver, spleen, and lymphatic system. | * The course of [[disease]] involves spread of the organism to multiple [[Organ (biology)|organ]] systems, including the [[lungs]], [[liver]], [[spleen]], and [[lymphatic system]]. | ||
* The course of disease is similar regardless of the route of exposure. Mortality in untreated (pre-antibiotic-era) patients has been as high as 50% in the | * The course of [[disease]] is similar regardless of the route of exposure. [[Mortality]] in untreated (pre-antibiotic-era) patients has been as high as 50% in the pneumonic and typhoidal forms of the disease, which however account for less than 10% of cases.<ref>http://www.cidrap.umn.edu/cidrap/content/bt/tularemia/biofacts/tularemiafactsheet.html#_Overview_1</ref> | ||
* Overall mortality was 7% for untreated cases, and the disease responds well to antibiotics with a fatality rate of about 2%. | * Overall [[mortality]] was 7% for untreated cases, and the disease responds well to [[antibiotics]] with a [[Fatality rate|fatality]] rate of about 2%. | ||
* The exact cause of death is unclear, but it is thought be a combination of multiple organ system failures. | * The exact cause of death is unclear, but it is thought be a combination of multiple [[Organ failure|organ]] system failures. | ||
== References == | == References == |
Revision as of 15:07, 22 March 2016
Tularemia Microchapters |
Diagnosis |
---|
Treatment |
Case Studies |
Francisella On the Web |
American Roentgen Ray Society Images of Francisella |
Francisella | ||||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|
Scientific classification | ||||||||||||
| ||||||||||||
Species | ||||||||||||
WikiDoc Resources for Francisella |
Articles |
---|
Most recent articles on Francisella Most cited articles on Francisella |
Media |
Powerpoint slides on Francisella |
Evidence Based Medicine |
Clinical Trials |
Ongoing Trials on Francisella at Clinical Trials.gov Clinical Trials on Francisella at Google
|
Guidelines / Policies / Govt |
US National Guidelines Clearinghouse on Francisella
|
Books |
News |
Commentary |
Definitions |
Patient Resources / Community |
Patient resources on Francisella Discussion groups on Francisella Patient Handouts on Francisella Directions to Hospitals Treating Francisella Risk calculators and risk factors for Francisella
|
Healthcare Provider Resources |
Causes & Risk Factors for Francisella |
Continuing Medical Education (CME) |
International |
|
Business |
Experimental / Informatics |
Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]
Overview
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.[2]
Causes
Causative Agent
- The type species, F. tularensis, causes the disease tularemia or rabbit fever.[3] 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.
- F. tularensis is found in widely diverse animal hosts and habitats and can be recovered from contaminated water, soil, and vegetation.
- A variety of small mammals, including voles, mice, water rats, squirrels, rabbits, and hares are natural reservoirs of infection.
- They acquire infection through tick, fly, and mosquito bites and by contact with contaminated environments.
- Epizootics with sometimes extensive die-offs of animal hosts may herald outbreaks of tularemia in humans.
- Humans can become incidentally infected through diverse environmental exposures: bites by infected arthropods; handling infectious animal tissues or fluids; direct contact with or ingestion of contaminated food, water, or soil; and inhalation of infective aerosols.
- Humans can develop severe and sometimes fatal illness, but do not transmit the disease to others.
Genomics
- Studies conducted on a strain of the Schu S4 genome report a genome size of less than 2 Mbp.
- F. tularensis is composed of a large majority of genes, unique to the species.
- Lesser amount of genes responsible for the encoding of transport and binding.
- There are few matches for genes responsible for gene regulation and energy metabolism between F. tularensis and other documented
Pathogenesis
Mechanism of infection
- Francisella tularensis is one of the most infectious bacteria known; fewer than ten organisms can cause disease leading to severe illness.
- The bacteria penetrate into the body through damaged skin and mucous membranes, or through inhalation.
- Humans are most often infected by tick bite or through handling an infected animal. Ingesting infected water, soil, or food can also cause infection.
- Tularemia can also be acquired by inhalation; hunters are at a higher risk for this disease because of the potential of inhaling the bacteria during the skinning process.
- Tularemia is not spread directly from person to person.
- Francisella tularensis is an intracellular bacterium, meaning that it is able to live as a parasite within host cells.
- It primarily infects macrophages, a type of white blood cell. It is thus able to evade the immune system.
- The course of disease involves spread of the organism to multiple organ systems, including the lungs, liver, spleen, and lymphatic system.
- The course of disease is similar regardless of the route of exposure. Mortality in untreated (pre-antibiotic-era) patients has been as high as 50% in the pneumonic and typhoidal forms of the disease, which however account for less than 10% of cases.[4]
- Overall mortality was 7% for untreated cases, and the disease responds well to antibiotics with a fatality rate of about 2%.
- The exact cause of death is unclear, but it is thought be a combination of multiple organ system failures.
References
- ↑ Allen LA (2003). "Mechanisms of pathogenesis: evasion of killing by polymorphonuclear leukocytes". Microbes Infect. 5 (14): 1329–35. PMID 14613776.
- ↑ Ryan KJ; Ray CG (editors) (2004). Sherris Medical Microbiology (4th ed. ed.). McGraw Hill. pp. 488&ndash, 90. ISBN 0-8385-8529-9.
- ↑ Collins FM (1996). Pasteurella, Yersinia, and Francisella. In: Baron's Medical Microbiology (Baron S et al, eds.) (4th ed. ed.). Univ of Texas Medical Branch. ISBN 0-9631172-1-1.
- ↑ http://www.cidrap.umn.edu/cidrap/content/bt/tularemia/biofacts/tularemiafactsheet.html#_Overview_1