The processing of stool samples will depend on the location of the study and will be detailed in the study SOPs. In brief, stool samples will be collected by study staff and either stored at 4 °C or inoculated in a transport medium until reception in the central laboratory. Stool samples will then be plated on a MacConkey agar plate containing ciprofloxacin. After incubation, colonies will be identified using standard microbiological methods. The minimum inhibitory concentration of ciprofloxacin and third-generation cephalosporins will be determined , and 10% of samples will be sent to a reference laboratory for quality control purposes.