Shigella dysenteriae

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Shigella dysenteriae
Scientific classification
Kingdom: Bacteria
Phylum: Proteobacteria
Class: Gamma Proteobacteria
Order: Enterobacteriales
Family: Enterobacteriaceae
Genus: Shigella
Species: S. dysenteriae
Binomial name
Shigella dysenteriae
(Shiga 1897)
Castellani & Chalmers 1919

Shigella dysenteriae is a species of the rod-shaped bacterial genus Shigella.[1][page needed] Shigella species can cause shigellosis (bacillary dysentery). Shigellae are Gram-negative, nonspore-forming, facultatively anaerobic, nonmotile bacteria.[2]

S. dysenteriae, spread by contaminated water and food, causes the most severe dysentery because of its potent and deadly Shiga toxin, but other species may also be dysentery agents.[3] Contamination is often caused by bacteria on unwashed hands during food preparation, or soiled hands reaching the mouth.[citation needed]

Signs and symptoms[edit]

The most commonly observed signs associated with Shigella dysentery include colitis, malnutrition, rectal prolapse, tenesmus, reactive arthritis, and central nervous system problems. Further, Shigella dysenteriae is associated with the development of hemolytic uremic syndrome, which includes anemia, thrombocytopenia, and renal failure.

Diagnosis[edit]

Since the typical fecal specimen is not sterile, the use of selective plates is mandatory. XLD agar, DCA agar, or Hektoen enteric agar are inoculated; all give colorless colonies as the organism is no t a lactose fermenter. Inoculation of a TSI slant shows an alkaline slant and acidic, but with no gas, or H2S production. Following incubation on SIM, the culture appears nonmotile with no H2S production. Addition of Kovac's reagent to the SIM tube following growth typically indicates no indole formation (serotypes 2, 7, and 8 produce indole[4]).

Shigella flexneri will produce acid and gas from glucose, and Shigella sonnei is mannitol and ornithine positive, and is also a late lactose fermenter (ONPG positive). Some Shigella species can produce indole.

See also[edit]

References[edit]

  1. ^ Ryan, Kenneth James; Ray, C. George, ed. (2004). Sherris medical microbiology: an introduction to infectious diseases (4 ed.). McGraw-Hill Professional Med/Tech. ISBN 978-0-8385-8529-0. 
  2. ^ Hale, Thomas L.; Keusch, Gerald T. (1996). "Shigella: Structure, Classification, and Antigenic Types". In Baron, Samuel. Medical microbiology (4 ed.). Galveston, Texas: University of Texas Medical Branch. ISBN 978-0-9631172-1-2. Retrieved February 11, 2012. 
  3. ^ Herold S, Karch H, Schmidt H (2004). "Shiga toxin-encoding bacteriophages--genomes in motion". International Journal of Medical Microbiology 294 (2–3): 115–121. doi:10.1016/j.ijmm.2004.06.023. PMID 15493821. 
  4. ^ Germani, Y.; Sansonetti, P.J. (2006). "Chapter 3.3.6: The Genus Shigella". In Dworkin, M. (editor-in-chief). The Prokaryotes: Proteobacteria: gamma subclass. Volume 6 (3rd ed.). New York: Springer. pp. 99–122. doi:10.1007/0-387-30746-x_6. ISBN 0-387-25496-X.