Urine is normally a sterile body fluid but, while leaving the body, it can become infected by bacteria. A common way for urine to contract bacteria is when it is kept in an infected bladder, which provides a fertile environment for bacteria to grow. Bacteria is the main cause of urinary tract infections. When a large concentration of bacteria is in the urine, it also could result in Asymptomatic bacteriuria, a harmless condition that often requires no treatment.
Escherichia coli (E. coli)
A micro-organism usually found in the digestive system, E. coli is said to be the main cause of urinary tract infections. Although E. coli normally lives in the colon, it can sometimes stick to the opening of the urethra (the passage of the urine from the bladder) causing an infection as it multiplies and travels through the urethra. Strands of E. coli can affect any part of the urinary system, which consists of the urethra, bladder, ureters and kidneys. When affected, each part develops a different infection. Urethritis, cystitis and pyelonephritis are infections of the urethra, bladder and kidneys correspondingly.
Mycoplasma and Chlamydia
Unlike E. coli, these microorganisms are sexually transmitted and require both partners to be treated in order to be completely eradicated. Most bladder infections arise from mycoplasma and chlamydia bacteria but a common symptom is the presence of pus in the urine. Detecting these microbes is often difficult when using a standard urine culture. However, they can easily be identified through special bacterial cultures.
Some microbes, such as lactobacillus, are normal in small amounts in the urine. Lactobacillus is a common vaginal contaminant that is usually present in women's urine and can cause infections when found in excessive amounts. A doctor can prescribe precautionary antibiotics to a patient at risk of developing an infection from lactobacillus.
Proteus and Other Microorganisms
A high pH in the urine is often a good indication of a proteus infection. Proteus bacterium is a recognised cause for the formation of urinary tract stones, which harbour bacteria that escape antibiotics. Microbes such as Klebsiella and enterococcus are also commonly found in urine, especially in women who are more prone to infections than men. Some bacteria that are less frequently present in urine, for example Candida albicans, Haemophilus influenzae, Mycobacterium tuberculosis, salmonella and staphylococcus usually make their way into the urinary system through the blood or lymphatic systems.