Causative organism of HUS is

Hemolytic-uremic syndrome (HUS) often occurs after a gastrointestinal infection with E coli bacteria (Escherichia coli O157:H7). However, the condition has also been linked to other gastrointestinal infections, including shigella and salmonella.Shigella spp:General characteristicsCultural characteristics*Gram negative bacilli*Non motile, non-capsulated *Selective media - DCA agar, XLD agar, SS agar*Enrichment broth - Gram-negative broth, Selenite F broth, Tetrathionate brothBiochemical reactionsVirulence factors *Ferment mannitol except for S.dysenteriae*Catalase positivity except S.dysenteriae type 1*Lactose non-fermenters except S.sonnei (Late lactose fermenter)*Invasiveness of Shigella - Virulence marker antigen*Endotoxin - LPS*Heat labile exotoxin (Shiga toxin) - Chromosome coded toxin produces neurotoxicity on blood vessel on CNS Clinical features*Infective dose - 10-100 organisms *Gay bowel syndrome*S.flexneri(50-85%)>S.dysenteriae(8-25%)>S.sonnei(2-24%)>S.boydi(0-8%)*Reactive ahritis (S.flexneri), toxic neuritis*Intussusceptions, HUS*Toxic dilatation, Colonic perforation *Reiter's syndrome *Thrombotic thrombocytopenic purpura DiagnosisTreatment*Specimen - Mucus flakes of stool*Stool culture diagnostic on XLD agar*Sereny test*Mild to moderate dehydration - ORS*Severe cases - Ampicillin or Cotrimoxazole*DOC for MDR pathogen - Nalidixic acid Ref: Ananthanarayan 9th edition, 279 & 287