Infections of the urinary tract affect 8 million to 10 million individuals annually. Although the urinary tract is anatomically designed to prevent colonization of microorganisms, about 40 percent of women and 12 percent of men seek treatment for urinary tract infections (UTI) at some point in their life. Characterized by frequent, painful and bad smelling urination, lower abdominal pain, mild fever, nausea and vomiting, UTIs start in the urethra (opening of the urinary tract) and may move up to the bladder, ureters and kidneys.
Causative Organisms
Most bacteria that cause UTIs are part of the normal organisms in the anal opening, which is in close proximity to urethra. Escherichia coli (E.coli) is the most common cause of uncomplicated infections of the lower urinary tract and accounts for almost 80 percent of all UTIs. Staphylococcus saprophyticus is responsible for 5 to 15 percent of UTIs, especially in younger women. Klebsiella sp., Enterococcus sp. and Proteus mirabilis are some of the other bacteria that cause the infections of the urinary tract, especially in older women.
Rare causes of the disease include Ureaplasma urealyticum, Citrobacter sp. and the fungal species called Candida albicans, more commonly known as yeast. Pseudomonas aeruginosa, Enterobacter sp. and Serratia sp. are associated with more complicated and severe infections of the urinary tract. Microorganisms called Chlamydia sp. and Mycoplasma sp. may be transmitted during sexual intercourse but these infections are usually limited to the urethra.
Contributing Factors
Lack of hygiene is the most important factor responsible for transmitting the bacteria from the anal and the vaginal openings to the urinary tract. Anatomy is another important factor, and women are more likely to have urinary tract infections compared to men. A longer urethra and the bactericidal properties of the prostatic fluid make men more resistant to E.coli and other bacteria. Individuals with a block in the urinary tract due to kidney stones or enlarged prostrate, catheterized patients in the hospitals and those with a suppressed immune system are more prone to UTIs. These infections are also more common in sexually active men and women. Women using diaphragms for birth control have shown increased susceptibility to urinary tract infections.
Causes of Recurrent Infections
Women with UTI have a 20 percent chance of having another one, and women who have had two UTIs have 30 percent chance of having a third one. Women who have had more than two UTIs have an 80 percent chance of recurrences. Recurrent infections are defined as having two infections in 6 months or three infections in one year. The microorganism responsible for the recurrent infection is, usually, different from the first one, suggesting that each infection is a separate one. Early research has suggested that a compromised immune system and attachment of the bacteria to the linings of the urinary tract are responsible for recurrent infections.
References
- "Medical Microbiology"; Patrick R. Murray, Ken S.Rosenthal, George S. Kobayashi, Michael A. Pfaller; 2005
- National Kidney and Urologic Diseases Information Clearinghouse: Urinary Tract Infections in Adults
- University Of Maryland Medical Center: Urinary Tract Infection-Causes
