 1. State of the issue and objective of the research The acute pyelonephritis AP represent the most frequent COMMUNAUTARY bacterial infection. Currently, usual recommended duration of antibiotherapy for this disease is from 10 to 21 days. The duration of treatment is not based on scientific evidence. Shortening duration of antibiotherapy would improve patients life quality of and compliance and reduce side effects, duration of hospitalization, cost of treatment and probably limit bacterial resistance. 