Between July , 2011 , and September , 2013 , hospital inpatients aged 18 years or older who had pyuria and a diagnosis of a complicated lower-urinary-tract infection or pyelonephritis were randomly assigned in a 1:1 ratio to receive intravenous 15 g ceftolozane-tazobactam every 8 h or intravenous high-dose ( 750 mg ) levofloxacin once daily for 7 days .