Urinary tract infections (UTIs) are caused by bacteria infecting the urethra and traveling up the urinary tract. These infections can ascend to cause an infection of the bladder (cystitis) and the kidney (pyelonephritis). Most urinary tract infections are more of an annoyance than a serious health problem, but kidney infections can lead to permanent renal impairment.
Forms
Urinary tract infections can be divided into two separate classes based on where they are acquired, the Merck Manual explains. Community acquired urinary tract infections describe any sort of bacterial infection that occurs outside of a medical setting. The causes for these kinds of infections are different than those found in patients who acquire their infection while hospitalized.
E. Coli
The E. coli bacteria accounts for approximately 80 percent of all cases of community acquired urinary tract infections, the Urology Channel explains. E. coli normally lives in the colon and can spread to the urethra from the rectum and anus. Sometimes this bacteria is able to spread as a result of wiping after defecation, particularly if the patient wipes form back to front. E. coli, according to the Merck Manual, also accounts for 50 percent of all hospital-acquired urinary tract infections.
Other Bacteria
Other strains of bacteria can also cause urinary tract infections. S. saprophyticus is the most common non-E. coli cause of community acquired urinary tract infections and can also infect patients in hospitals. Bacteria that can infect the urinary tracts of hospitalized patients include Klebsiella, Enterobacter, Serratia, Proteus, E. faecalis and S. aureus bacteria.
Sexually Transmitted Bacteria
Chlamydia and Mycoplasma are two classes of bacteria that can be sexually transmitted. According to the National Institute of Diabetes and Digestive and Kidney Disorders (NIDDK), these bacteria can also infect the urinary tract. The NIDDK notes, however, that these bacteria tend to stay in the urethra and reproductive system as opposed to traveling to the bladder and kidneys, as other bacteria can.
Risk Factors
Patients who have any abnormalities in their urinary system (such as bladder stones or an enlarged prostate) are more likely to develop urinary tract infections. Diabetics also have a higher risk of developing UTIs because of their weakened immune system. Bacteria can also gain access to the urinary tract through urinary catheters. Finally, women are at particular risk of developing urinary tract infections, partly due to their shortened urethra. Some women commonly develop UTIs after sexual intercourse
