Urinary Tract Infections
المؤلف:
Cornelissen, C. N., Harvey, R. A., & Fisher, B. D
المصدر:
Lippincott Illustrated Reviews Microbiology
الجزء والصفحة:
3rd edition , p375
2025-09-14
380
Urinary tract infections (UTIs) most commonly affect either the lower urinary tract (infection of the urethra or bladder) or, less frequently, the upper urinary tract (acute pyleonephritis, or infection of the kidney). UTIs are termed “uncomplicated” when there is no underlying condition that increases the risk of infection, such as obstruction or urologic dysfunction. Most patients with UTI have uncomplicated cystitis, which is one of the most common infections in the United States, especially in sexually active women.
Escherichia coli is the most common cause of uncomplicated cystitis and pyelonephritis (70 to 95 percent of infections, Figure 1). Fecal contamination can lead to entry of an organism such as E. coli (one of the most common facultative organisms found in stool) into the urethra. These bacteria then move up into the bladder (and sometimes ascend into the kidney), producing infection. UTIs occur much more frequently in women as a result of the proximity of the urethral opening to the anus and the shorter length of the urethra before it opens into the bladder in women.
Fig1. Disease summary of urinary tract infections. 1Uncomplicated cystitis.
Fig1. (continued) Disease summary of urinary tract infections. 1 Indicates first-line drugs; 2indicates alternative drugs.
Staphylococcus saprophyticus as a causative agent is a distant second to E. coli, causing 5 to 20 percent of infections. S. saprophyticus, although less common than E. coli, often presents as a more aggressive disease with approximately one half of the patients showing involvement in the upper urinary tract. These patients are also more likely to have recurrent infection.
Patients with uncomplicated UTI usually present with dysuria, urinary frequency, urinary urgency, and/or suprapubic pains. Pyuria (the production of urine that contains white blood cells) is commonly found in UTIs. Fever or flank tenderness could indicate pyelonephritis. If the features suggestive of vaginitis or urethritis described above are present, a pelvic examination and appropriate cultures should be per formed.
The risk of UTI, both cystitis and pyelonephritis, can be increased by several factors, especially sexual intercourse, particularly with a new sexual partner. The use of spermicides, particularly in combination with a diaphragm, also increases the risk of a woman developing a UTI.
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