What is the primary causative agent associated with hemolytic uremic syndrome in children?

The primary causative agent associated with hemolytic uremic syndrome (HUS) in children is Escherichia coli, particularly the strain O157:H7. This strain is a type of Shiga toxin-producing E. coli (STEC) that is commonly associated with outbreaks of foodborne illness, primarily through contaminated food products such as undercooked ground beef or unpasteurized milk and juices.

HUS is characterized by a triad of symptoms: hemolytic anemia, acute renal failure, and thrombocytopenia. The infection with this strain of E. coli can lead to the release of Shiga toxin into the bloodstream, which damages the endothelial cells of the blood vessels, particularly in the kidneys. This damage results in the clinical features of HUS.

In contrast, other pathogens listed, such as Salmonella, Shigella, and Campylobacter, are associated with gastrointestinal infections and can lead to other complications but are not prominently linked to HUS in the pediatric population. HUS is most distinctly associated with STEC infections, making E. coli the correct answer in this context.