SHIGELLABy: Hunter Reynolds

Scientific name

• Hylobates concolor

Classification• Strains-A study of the nutritional requirements of five strains of Shigella flexneri

serotype 3 was carried out.

• Shape-Circular DNA genome.

• Shigella is its own clade.

• Gram negative bacilli

Metabolism• Shigella pathogens use a mixed acid fermentation pathway to metabolize substrates.

Products of this anaerobic pathway include ethanol, acetic acid, lactic acid, succinic

acid, formic acid, and carbon dioxide.

• It is an auto transporter.

• Facultative anaerobes

• The intra- and inter-cellular spreading phenotypes

Habitat

• The intestinal tract of infected humans.

• Humans are the only reservoir for Shigella. Transmitted by the fecal-oral route.

Special adaptations • Transcriptional adaptation

• invades epithelial cells as well as macrophages and dendritic cells and escapes into the cytosol soon after invasion

• 929 and 1,060 genes were up- or down-regulated within HeLa cells and U937 cells

• The production of invasion plasmid antigens (Ipa) that have a direct role in the Shigella invasion process

• Adhesins that are involved in the adherence of bacteria onto the surface of target epithelial cells

Disease causing• Symptoms of shigellosis include diarrhea, bloody stool, abdominal cramps, and fever.

The incubation period is 1-3 days

• Initial profuse watery diarrhea typically appears first as a result of enterotoxin. Within 1-2 days this progresses to Abdominal cramps and tenesmus, with or without bloody stool. Classic shigellosis presents itself as lower abdominal cramps and stool abundant with blood and pus develops as the Shigella invade the mucosa of the colon.

• It is an endotoxin.

gram

• Shigella is a negative gram.

Function• Infection by the gram-negative bacterium Shigella flexneri results in dysentery, an

acute inflammatory disease of the colon

• the pathogenesis of Shigella infections include bacterial invasion of epithelial cells, escape from the phagosome, and induction of apoptosis in macrophages

• Induction of apoptosis is dependent on IpaB binding to the cysteine protease caspase-1 (Casp-1). The activation of this enzyme triggers both apoptosis and release of the proinflammatory cytokine interleukin

WOW• In the UK and other developed countries most cases of infection (>90%) are due to S.

sonnei and to a much lesser extent S. flexneri, while in developing countries S. dysenteriae and S. flexneri are the commonest species

• The organism invades the cells lining the large bowel and multiplies there, killing the cell; this is the cause of the symptoms produced

• Shigella infections may also be acquired from contaminated food, vegetables harvested from fields with sewage in it, flies that breed in the infected feces and then

contaminate food or by drinking or swimming in contaminated water.

• By: Hunter Reynolds