Introduction

Acute lower urinary tract infections (UTI, also called acute bacterial cystitis) are responsible for 3.6 million office visits in the US each year, accounting for $1.6 billion in direct costs. Acute bacterial cystitis in the otherwise healthy nonpregnant adult woman is termed an uncomplicated UTI. A complicated UTI is any infection in the setting of anatomic urinary tract abnormalities, indwelling catheters, recent urinary tract instrumentation, pregnancy, recent antimicrobial administration, immunosuppression (including diabetes mellitus), atypical symptoms or symptoms lasting more than 7 days. If any of these factors are present, it increases the likelihood of treatment failure and warrants consideration of parenteral treatment, culture-based treatment or empiric treatment with broad-spectrum antibiotics.

Urinary tract infections develop when bacteria from the gastrointestinal tract colonize the vagina and enter the urethra. In a meta-analysis of 3108 women with acute cystitis, 78.6% were caused by Escherichia coli, followed by Staphylococcus saprophyticus (4.4%), Klebsiella pneumoniae (4.3%), and Proteus mirabilis (3.7%). Citrobacter, Enterococcus and Pseudomonas are occasional causes of UTI. Sexual activity is the most important risk factor for development of UTI.

The primary symptoms of acute cystitis are dysuria, frequency, urgency, suprapubic pain, and/or hematuria. Suprapubic urine aspiration and culture is the gold standard for diagnosis of urinary tract infection; however, patient discomfort, cost and delay in culture results have led clinicians to look for more convenient and rapid diagnostic techniques. In most patients with symptoms of acute cystitis (dysuria, frequency or urgency), urine culture is not necessary as these symptoms in an otherwise healthy individual are highly sensitive for a UTI. Evaluation of mid-stream urine for pyuria has a high sensitivity (95%) but a relatively low specificity (71%) for infection; its absence strongly suggests a noninfectious cause for the symptoms. The presence of visible bacteria on microscopic examination is less sensitive but more specific. Urine dipstick testing has largely supplanted microscopy and urine cultures, because the dipstick method is cheaper, faster and more convenient. Dipsticks are most accurate when the presence of nitrite or leukocyte esterase is detected. The presence of gross or microscopic hematuria is helpful since it is common in women with UTI but not in women with urethritis or vaginitis. Hematuria is not a predictor for complicated infection and does not warrant extended therapy. In patients with a complicated infection, atypical symptoms, recurrent symptoms (less than 1 month after prior treatment) or failure to respond to initial therapy, urine culture is indicated and should guide treatment choice.

When obtaining a clean voided urine sample for urine dipstick testing or urine culture, patients should be given clear instructions on urine collection. The urethral meatus should be cleansed with a nonfoaming antiseptic solution. The labia should be held apart to minimize local contamination from skin flora. The first part of the stream is likely to be contaminated and should be discarded before collection of a mid-stream sample in a sterile container. Samples should be taken rapidly to the laboratory or placed on ice, as bacterial replication in the sample container may result in elevated bacterial counts. The first voided specimen in the morning is likely to demonstrate higher bacterial counts but is impractical in the clinical setting. Patients with indwelling catheters should have sampling directly from the catheter with a sterile needle and syringe. Samples taken directly from the catheter bag are usually contaminated.

Bacteriuria is defined as the culture from a voided urine specimen greater than 105 cfu/mL of a single micro-organism. The isolation of less than 105

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