Acute Uncomplicated Urinary Infection

Acute uncomplicated urinary infection, or acute cystitis, is infection occurring in individuals with a normal genitourinary tract and no recent instrumentation. It is a common syndrome that occurs virtually entirely in women; 60% of all women experience at least one infection in their lifetime. From 1% to 2% of women have frequent recurrent infection. The highest incidence is in young, sexually active women. Risk factors for infection in these women are both genetic and behavioral. Women with recurrent acute uncomplicated urinary infection are more likely to have first-degree female relatives with urinary infections and to be nonsecretors of blood group substances. Polymorphisms of genes encoding elements of the innate immune response may also contribute to the genetic propensity to recurrent infection. Sexual activity is strongly associated with infection in premenopausal women, and frequency of infection correlates with frequency of intercourse. The use of spermicides or a diaphragm for birth control also increases the risk for infection; risk is not increased by use of oral contraceptives or condoms without spermicide. Behavioral practices such as postvoid personal hygiene, type of underwear, postcoital voiding, or bathing rather than showering have no association with infection. For postmenopausal women, frequency of sexual intercourse is not a risk factor for infection. The most important predictor of infection in older women is a history of urinary infection at a younger age.

Escherichia coli is isolated from 80% to 85% of episodes. Staphylococcus saprophyticus , a coagulase-negative staphylococcus, occurs in 5% to 10% of episodes. This organism is rarely isolated in other clinical syndromes and has a unique seasonal variation with increased frequency in the late summer and early fall. Klebsiella pneumoniae and Proteus mirabilis are each isolated in 2% to 3% of cases. Organisms that cause infection originate from the normal gut flora, colonize the vagina and periurethral area, and ascend to the bladder. Women with urinary infection frequently have alterations in vaginal flora characterized by decreased or absent hydrogen peroxide (H ₂ O ₂ ) producing lactobacilli, resulting in increased vaginal pH and facilitating colonization with E. coli and other potential uropathogens.

The clinical presentation, diagnosis, and recommended treatment for acute uncomplicated urinary infection are summarized in Table 47.2 . New-onset frequency, dysuria, and urgency together with the absence of vaginal discharge or pain are 90% accurate to diagnose infection. From 30% to 50% of women have quantitative counts of less than 10 ⁵ cfu/mL of a uropathogen isolated from the urine specimen. Thus, any quantitative count of a potential uropathogen with pyuria is considered sufficient for microbiologic diagnosis when accompanied by consistent clinical symptoms. Because the clinical presentation is characteristic, the bacteriology is predictable, and the quantitative microbiology is often not definitive, it is recommended that symptomatic episodes be managed with empiric antimicrobial therapy and routine pretherapy urine culture not be obtained. A urine specimen for culture should be obtained before antimicrobial treatment if there is uncertainty about the diagnosis, failure of an initial therapeutic regimen, or early recurrence after therapy. The differential diagnosis includes urethritis due to sexually transmitted diseases such as Neisseria gonorrhoeae or Chlamydia trachomatis , yeast vulvovaginitis, or genital herpes.

Antimicrobial therapy is selected based on considerations of patient tolerance, documented efficacy for treating urinary infection, and local prevalence of resistance in community-acquired E. coli . Recommended therapy is nitrofurantoin for 5 days, single-dose fosfomycin trometamol, or, when available, 5 days of pivmecillinam; all of these have indications virtually limited to treatment of this syndrome. Trimethoprim-sulfamethoxazole (TMP/SMX) has been the recommended empiric therapy for many years. However, if the regional prevalence of resistance of community E. coli isolates to this antimicrobial is over 20%, an alternate empiric regimen should be prescribed. Fluoroquinolones and β-lactam antimicrobials are not considered first-line therapy because of the propensity to induce resistance in gut flora and, for β-lactams, a lower efficacy. The increasing global resistance of community E. coli , especially the widespread dissemination of extended-spectrum beta-lactamase (ESBL) or carbapenemase-producing strains, is a current concern. These organisms are also usually resistant to TMP/SMX and fluoroquinolones, but, to date, most remain susceptible to nitrofurantoin, fosfomycin, and pivmecillinam. A 3-day course of antimicrobial therapy with TMP/SMX or a fluoroquinolone is effective. A longer course of 7 days is recommended when the duration of symptoms is more than 7 days, for women with an early recurrence of symptomatic infection (<30 days) following prior antimicrobial therapy, and when treatment is with a β-lactam antimicrobial.

For women with mild to moderate symptoms, about 50% are symptom free by 7 days following initiation of antiinflammatory therapy and without antibiotics. Antibiotic therapy, however, clearly decreases symptom duration. Some women with mild symptoms may choose to delay antimicrobial therapy to see if spontaneous resolution occurs with antiinflammatory medication, but whether to delay antibiotics should be a patient decision.

Frequent recurrent acute cystitis is a disruptive and distressing problem for many women. Antimicrobial prophylaxis, given either as a long-term, low-dose regimen or after intercourse, prevents 95% or more of recurrent episodes and is usually recommended for women with two episodes in 6 months or 3 in 1 year ( Table 47.3 ). Increasing resistance of E. coli strains may limit the effectiveness of TMP/SMX. Continuous low-dose prophylaxis taken at bedtime is recommended, with an initial course of 6 to 12 months. This remains effective when taken for as long as 2 to 5 years. When prophylactic therapy is discontinued, the frequency of urinary infection is similar to that observed before prophylaxis. Approximately 50% of women have recurrent infection within 3 months. Postcoital prophylaxis is, obviously, most appropriate for women who identify sexual intercourse as a precipitating factor for recurrent symptomatic episodes. An alternate approach preferred by some women, especially with less frequent recurrences or who are concerned about developing an infection while traveling, is self-treatment. This approach is effective with short-course TMP/SMX, ciprofloxacin, or ofloxacin. It is appropriate for women who are compliant with management and reliable in identifying their symptomatic episodes.

The most important nonantimicrobial intervention for prevention of recurrent urinary infection is avoidance of spermicide use. The daily intake of cranberry or lingonberry juice or cranberry tablets was previously reported to decrease the frequency of recurrent infection by 30%, but recent blinded placebo-controlled trials have not reported a benefit. Vaccines to prevent recurrent uncomplicated urinary infection and use of probiotics to reestablish normal gut or vaginal flora are being investigated, but studies to date have not shown consistent benefits with either of these approaches.