<prompt> Causative organism of HUS isETECShigella dysenteriaeSalmonellaPseudomonas  <response>: 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 characteristicsGram negative bacilliNon motile, non-capsulated Selective media - DCA agar, XLD agar, SS agarEnrichment broth - Gram-negative broth, Selenite F broth, Tetrathionate brothBiochemical reactionsVirulence factors Ferment mannitol except for S.dysenteriaeCatalase positivity except S.dysenteriae type 1Lactose non-fermenters except S.sonnei Late lactose fermenterInvasiveness of Shigella - Virulence marker antigenEndotoxin - LPSHeat labile exotoxin Shiga toxin - Chromosome coded toxin produces neurotoxicity on blood vessel on CNS Clinical featuresInfective dose - 10-100 organisms Gay bowel syndromeS.flexneri50-85S.dysenteriae8-25S.sonnei2-24S.boydi0-8Reactive ahritis S.flexneri, toxic neuritisIntussusceptions, HUSToxic dilatation, Colonic perforation Reiters syndrome Thrombotic thrombocytopenic purpura DiagnosisTreatmentSpecimen - Mucus flakes of stoolStool culture diagnostic on XLD agarSereny testMild to moderate dehydration - ORSSevere cases - Ampicillin or CotrimoxazoleDOC for MDR pathogen - Nalidixic acid Ref: Ananthanarayan 9th edition, 279 287 