Infections of the upper and lower urinary tract account for more than 6 million office visits per year in the US, costing more than $2.5 billion annually. 50 to 60% of women report at least one UTI in their lifetime. The key UTI challenge is however in intensive care units (ICUs), where urinary catheters are used routinely. Urinary tract infections in critically ill patients are associated with increased length of hospital stay and mortality. Complicated UTIs account for 32% of all health care associated infections and are the most common nosocomial infections in ICUs. Approximately 80% of the bacteria isolated in UTIs are Gram-negative bacteria from the large family Enterobacteriaceae. These include Escherichia coli, Klebsiella and Enterobacter. Another Gram-negative bacterium, P. aeruginosa, and various Gram-positive bacteria are other common pathogens. As E. coli is the most frequently isolated bacteria from patients, third generation cephalosporins are the most widely recommended antibiotics.