Assessing the Impact of Unnecessary Antibiotic Treatment on the Development of Appropriate Adaptive Immune Responses in Malnourished Bangladeshi Infants

The investigators are examining the role of circulating T follicular helper (Tfh) cells in the induction of the antibody responses. The investigators hypothesize that Tfh cell activation is impaired in Bangladeshi children and that this activation failure is associated with a history of antibiotic use. The results of the investigators' preliminary studies suggest that antibiotic treatment could have a detrimental effect on the development of an appropriate adaptive immune response against Cryptosporidium. Antibiotic treatment for children with cryptosporidiosis, rotavirus and adenovirus 40/41is not currently recommended (supportive therapy only), although usually given to children in Dhaka, Bangladesh. This study will randomly assign children with diarrhea due to Cryptosporidium, rotavirus or adenovirus 40/41 to two groups. Supportive treatment would be provided in both groups, but in group #1, antibiotic treatment would be withheld while group #2 will receive usual care which normally will include antibiotic treatment. The investigators will monitor the children for one year to measure T follicular helper function, antibody production, and reinfection.