Shigella dysenteriae

Taxobox
color = lightgrey
name = "Shigella dysenteriae"
regnum = Bacteria
phylum = Proteobacteria
classis = Gamma Proteobacteria
ordo = Enterobacteriales
familia = Enterobacteriaceae
genus =" Shigella"
species = "S. dysenteriae"
binomial = "Shigella dysenteriae"
binomial_authority = (Shiga 1897)
Castellani & Chalmers 1919

"Shigella dysenteriae" is a species of the rod-shaped bacterial genus "Shigella".cite book | author = Ryan KJ, Ray CG (editors) | title = Sherris Medical Microbiology | edition = 4th ed. | publisher = McGraw Hill | year = 2004 | id = ISBN 0838585299 ] Shigella can cause shigellosis (bacillary dysentery). Shigellae are Gram-negative, non-spore-forming, facultatively anaerobic, non-motile bacteria.cite book | author = Hale TL, Keusch GT | title = Shigella. "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.chapter.1257 | id = ISBN 0-9631172-1-1 ]

"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. [cite journal |author=Herold S, Karch H, Schmidt H |title=Shiga toxin-encoding bacteriophages--genomes in motion |journal=Int. J. Med. Microbiol. |volume=294 |issue=2-3 |pages=115–21 |year=2004 |pmid=15493821 |doi=]

Diagnosis

A stool specimen is Gram-stained to show G - ve, rods, with no particular arrangement. Enrichment is performed by growing the organisms on Selenite-F broth. Then, since the specimen is not sterile, the use of selective plates is mandatory. XLD agar, DCA agar, or HE agar are inoculated and colonies are colorless on all of them as the organism is non-lactose fermentor. TSI slant would show a profile of (K/A/H₂S-/g-), and SIM would appear (+/-/+).

It's noteworthy that "Shigella flexneri" will produce acid and gas from glucose, and "Shigella sonnei" is mannitol and ornithine positive, and is also late lactose fermentor (ONPG positive). Some "Shigella" species are capable of producing indol.

References