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Infections of the urinary tract represent a wide variety of syndromes, including urethritis, cystitis, prostatitis, and pyelonephritis. Urinary tract infections are one of the most commonly occurring bacterial infections in medicine today and account for 7 million patient visits annually.(1) It is estimated that 20% of women will suffer a symptomatic urinary tract infection some time in their lives, with many having multiple recurrences.(2) Under normal circumstances, the urinary tract is generally resistant to infection and colonization by bacteria, owing at least in part to the properties of urine itself. Its low pH, high concentration of urea, and extremes in osmolality help to inhibit or kill many microorganisms.
Infections of the urinary tract are classified by several methods, one being the anatomic site of involvement. Lower urinary tract infections include cystitis (bladder), urethritis (urethra), prostatitis (prostate gland), and epididymitis. Pyelonephritis is considered an upper urinary tract infection and involves the kidneys.
UTIs are also classified as complicated or uncomplicated. Uncomplicated urinary tract infections involve a patient who lacks structural or functional abnormalities that interfere with normal urine flow. These infections occur most frequently in women of child bearing age who are otherwise healthy individuals.
Complicated UTIs are the result of predisposing lesions of the urinary tract, such as congenital abnormality or distortion of the urinary tract, a stone, indwelling catheter, prostatic hypertrophy, obstruction, or neurologic deficit that interferes with the normal flow of urine and urinary tract defenses. Complicated infections occur in both genders and frequently involve the upper and lower urinary tract.(3) UTIs are disorders involving a repeated or prolonged bacterial infection of the bladder or lower urinary tract. Most urinary tract infections occur in the lower urinary tract, which includes the bladder and urethra. Cystitis occurs when bacteria, with resultant inflammation infect the normally sterile lower urinary tract. Chronic or recurrent urinary tract infections include repeated episodes of cystitis (more than two occurrences in six months), or urinary tract infections that do not respond to usual therapies or that last longer than two weeks. UTIs are most common in women; however, men and children may experience them as well. About one in every five women will experience a UTI at least once in their lifetime, and many will have recurring infections. Also, the elderly population is at an increased risk for developing cystitis due to incomplete emptying of the bladder associated with such conditions as benign prostatic hyperplasia (BPH), prostatitis, and urethral strictures. Also, a lack of adequate fluids, bowel incontinence, immobility or decreased mobility, and placement in a nursing home, all place the person at increased risk for developing cystitis.(4)
The microbiologic etiology of urinary tract infections usually originates from the bowel flora of the host. The most common bacteria causing uncomplicated urinary tract infections is Escherichia coli, accounting for approximately 85% of community acquired infections. Staphlococcus saphrophyticus, Klebsiella pneumoniae, Proteus sp.,Pseudomonas aeruginosa, and enterococcus sp. are additional causative organisms. Staphlococcus epidermidis is frequently found and should be considered a contaminant unless repeat cultures are performed to help confirm the organism as a real pathogen. In hospitalized patients, the second most frequently found pathogen is Enterococcus faecalis.(5) In part, this finding may be related to the use of third-generation cephalosporin antibiotics, which are not active against enterococci. Enterococcus faecalis resistance to Vancomycin has become<
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