Hello dear Warm welcome to Healthcaremagic.com I have evaluated your query in details . * There are various organisms responsible for the UTI and accordingly the type of antibiotic molecule is decided by the treating consultant in association with clinical severity . * Usually e. coli is most common cause in many cases with good coverage from fluoroquinolones , macrolides , cephalosporin , penicillin group of antibiotics . * The advantage of change of antibiotic - better control of virulence of the organism - managing occurrence of drug resistance Wishing you fine recovery . Feel free to ask any further queries . Regards .