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Urinary tract infections (UTIs) account for at least 7 million outpatient visits and 1 million hospital admissions annually in the United States (US). Total costs associated with UTIs are significant, exceeding $1.6 billion for ambulatory women with UTIs.1,2

UTIs can occur in all people, but certain factors increase the likelihood of exposure to uropathogens. These factors include age, sex, pregnancy, diabetes, the presence of a urinary catheter, and vaginal intercourse.3 The overall self-reported annual incidence is 12.1% among women and 3% among men. Peak incidence among women (18.6%) occurs during ages 20 to 24 and peak incidence among men (7.3%) occurs in those 85 years and older.2

UTIs are divided into cystitis (lower tract and bladder) and pyelonephritis (upper tract and kidneys). Cystitis symptoms include dysuria, frequency, urgency, and occasionally suprapubic tenderness. Pyelonephritis is characterized as cystitis plus fever, flank pain, nausea, and vomiting.1,4-5 Uncomplicated UTIs are infections occurring in women of childbearing age with structurally and neurologically normal urinary tracts. Complicated UTIs occur in urinary tracts with functional or structural abnormalities. In general, UTIs in men, pregnant women, children, and patients who are hospitalized or in health care-associated settings are considered complicated. These infections are more likely to be caused by resistant organisms.5

A UTI diagnosis requires a symptomatic patient with a positive urinalysis and urine culture. A urinalysis will identify pyuria, which is defined as ≤10 leukocytes/mm3 of urine. Pyuria is nonspecific, and patients with pyuria may not have an infection. Urine in the bladder is normally sterile. Patients with a UTI usually have ≤105 bacteria/mL identified by culture.6 Any organism, including fungi and viruses, colonizing the urinary tract can cause a UTI, but most are caused by bacteria.3 The majority of uncomplicated UTIs are caused by gram-negative bacteria, with Escherichia coli being isolated in 70% to 95% of cultures. The most common gram-positive bacteria isolated are Staphylococcus saprophyticus and enterococci (Table 23-1).7

TABLE 23-1 Bacterial Causes of UTIs7

Asymptomatic bacteriuria is defined as the isolation of a specified quantitative count of bacteria in an appropriately collected urine specimen obtained from a person without symptoms or signs referable to urinary infection.8 The diagnosis of asymptomatic bacteriuria should be based on results of a urine culture. Pyuria accompanying asymptomatic bacteriuria is not an indication for therapy. Pregnant women should be screened for bacteriuria by urine culture at least once during early pregnancy (12-16 weeks gestation) ...

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