Antibiotic treatment for urinary tract infections: pharmacokinetic/pharmacodynamic principles

Bacterial urinary tract infections (UTIs) frequently occur in the outpatient as well as in the nosocomial setting. The stratification into uncomplicated and complicated UTIs has proven to be clinically useful. Bacterial virulence factors on the one hand, and the integrity of the host defense mechanisms on the other, determine the course of the infection. Late complications or sequelae might ensue if the defense mechanisms are disturbed, either by a genetic or an acquired cause. Escherichia coli is the most prevalent organism in uncomplicated UTIs, whereas the bacterial spectrum is much broader in complicated UTIs, including Gram-negative and -positive, and often multiresistant organisms. Therapy for uncomplicated UTIs is almost exclusively antibacterial, whereas in complicated UTIs the complicating factors need to be treated as well. The success of antibiotic therapy of UTIs in a population can be estimated by four parameters: the minimal inhibitory concentrations of the clinical isolates, the pharmacokinetic and pharmacodynamic profiles, and the protein binding of the treatment drug. In uncomplicated UTIs, antimicrobial therapy is usually empiric, whereas in complicated UTIs antibiotic therapy should be more individualized; tailored to the individual patient.