Urinary tract infections (UTI) | Treatment

Empiric treatment of Urinary Tract Infections

Urinary Tract Infections

Infections of the urinary tract represent a wide variety of clinical syndromes including urethritis, cystitis, prostatitis, and pyelonephritis. A urinary tract infection (UTI) is defined as the presence of microorganisms in the urine that cannot be accounted for by contamination. The organisms have the potential to invade the tissues of the urinary tract and adjacent structures.

Lower tract infections include cystitis (bladder), urethritis (urethra), prostatitis (prostate gland), and epididymitis. Upper tract infections involve the kidney and are referred to as pyelonephritis.

Empiric Treatment

UTIs are classified as “uncomplicated” or “complicated.” Uncomplicated UTIs are those that occur in young, healthy, nonpregnant women; complicated UTIs are all other UTIs. The typical complicated UTI would be an infection in a woman with diabetes or with a structural abnormality of her urinary system or who acquired her infection in the hospital. The differentiation between complicated and uncomplicated infections is important because it affects both the spectrum of bacteria involved and the duration of antibiotic treatment.


In uncomplicated acute cystitis and pyelonephritis, the causative bacteria are predictable. In most cases, Escherichia coli will be the etiologic organism. Staphylococcus saprophyticus, Proteus mirabilis, Klebsiella spp., and other Enterobacteriaceae are also sometimes cultured. Unlike their hospitalacquired counterparts, these community-acquired bacteria are usually susceptible to most antibiotics. In complicated UTIs, bacteria that are more antibiotic resistant, such as Pseudomonas aeruginosa, Enterobacter spp., Serratia spp., Citrobacter spp., and Staphylococcus aureus, assume a more prominent role, as do enterococci.

Recommended empirical treatment of acute uncomplicated cystitis is a 5-day course of nitrofurantoin. A 3-day course of oral trimethoprimsulfamethoxazole was formerly the treatment of choice; but because of increasing resistance, it is now only recommended if local resistance rates of uropathogens do not exceed 20% and this agent has not been used to treat a UTI in the preceding 3 months. Both nitrofurantoin and trimethoprim-sulfamethoxazole are effective against many of the E. coli, other Enterobacteriaceae, and S. saprophyticus strains that cause these infections.

The same bacteria that cause uncomplicated cystitis also cause uncomplicated pyelonephritis. The treatment recommendations, however, are different because nitrofurantoin does not achieve the high serum levels necessary to treat pyelonephritis-associated bacteremia and because the consequences of inappropriate treatment of resistant organisms with trimethoprim-sulfamethoxazole are more severe with pyelonephritis. Recommended treatment regimens depend on the severity of the disease, with oral agents being used for mild disease and intravenous therapy for severe disease.

For mild disease, oral quinolones (ciprofloxacin, levofloxacin) are often used empirically. Therapy for severe disease is with a parenteral quinolone (ciprofloxacin, levofloxacin); an aminoglycoside (gentamicin, tobramycin, amikacin), with or without ampicillin; an extended-spectrum penicillin (piperacillin, ticarcillin), with or without an aminoglycoside; a third-generation cephalosporin (ceftriaxone, cefotaxime), with or without an aminoglycoside; or a carbapenem (imipenem, meropenem, doripenem, ertapenem). Antimicrobial treatment for acute pyelonephritis should be continued for 7 to 14 days. Note that moxifloxacin is not approved for use in the treatment of UTIs.

Antibiotic therapy for complicated UTIs must be effective against the more resistant organisms that sometimes cause these infections.

Typical regimens include a quinolone (ciprofloxacin, levofloxacin), cefepime, carbapenem (imipenem, meropenem, doripenem, ertapenem), or extended-spectrum penicillin/β-lactamase inhibitor combination (piperacillin/tazobactam, ticarcillin/ clavulanate). If gram-positive bacteria are seen on Gram stain of the urine (suggesting the presence of enterococci), ampicillin

or amoxicillin should be added. Treatment is usually continued for 7 to 14 days or longer.


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