Most common cause of hemolytic uremic syndrome is –
Etiology of HUS

HUS usually follows an episode of acute gastroenteritis.
Less commonly, patient may present after an upper respiratory tract infection.
The organisms responsible are -
E.coli (most common) → EHEC (shiga toxin producing)           
Shigella dysenteriae     
Salmonella     
Bartonella   
Streptococcus pneumonia      
Campylobacter
E.coli
Shigella
Salmonella
Psedonomis