Assuming baseline prevalence of ciprofloxacin-resistant enterobacteriaceae of 20%, a sample size of 131 persons in each of the two arms would have 90% power to detect a change in the prevalence to 30% over the three repeated measures. Assuming an attrition rate of 25% and 20% of improperly collected samples, a sample size of 200 persons per arm would allow for the calculation of the primary resistance objective (community-wide prevalence of ciprofloxacin-resistant enterobacteriaceae) with sufficient power.