The analysis of the resistance sub-study will be done on the basis of the per-protocol population for whom all three stool samples are available. The primary sub-study outcome (change in community-wide prevalence of carriers of ciprofloxacin-resistant enterobacteriaceae) will be compared using the method described by Liu and Wu . Individual-level acquisition rates at 7 and 28 days following the initial sample will also be calculated with corresponding 95% confidence intervals using the binomial distribution. Acquisition will be defined as the presence of ciprofloxacin-resistant enterobacteriaceae at day 7 or day 28 in a participant who did not have ciprofloxacin-resistant enterobacteriaceae at the time of baseline sample collection. A Fisher exact test will be used to compare proportion of acquisition between study interventions. All tests will be two-sided with a significance threshold of α = 0.05.Due to the uncertainty of several parameters used in the sample size calculation, we plan to recruit for four weeks and perform a sample size re-estimation based on the estimated value of p 0, the attack rate in the controls, from this sub-sample. For this, we follow the method of Lake et al. . We make two assumptions in doing this: that epidemics in individual villages last only a short time, meaning the p 0 estimated 4–6 weeks after recruitment of a village will be very close to p 0 for that village at the end of the study; and that the attack rate in each village will remain constant during the whole course of the epidemic, i.e., that villages affected early in the epidemic do not have systematically bigger or smaller epidemics than villages affected later in the epidemic.