Urine culture

Bacteriuria
Multiple rod-shaped bacteria shown between the larger white blood cells at urinary microscopy from a patient with urinary tract infection.
Classification and external resources
MedlinePlus	000520
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In medicine, bacteriuria denotes the presence of bacteria in urine (but not if the bacteria's presence is due to contamination from urine sample collection.)

Bacteria in the urine, especially gram-negative rods, usually indicate a urinary tract infection (either cystitis or pyelonephritis), although bacteriuria can also occur in prostatitis. Escherichia coli is the most common bacterium isolated from urine samples.

Asymptomatic bacteriuria is bacteriuria without accompanying symptoms of a urinary tract infection (such as frequent urination, painful urination or fever). It is more common in women, in the elderly, in residents of long-term care facilities, and in patients with diabetes, bladder catheters and spinal cord injuries. Patients with a long-term Foley catheter uniformly show bacteriuria.

Chronic asymptomatic bacteriuria without urinary tract infection symptoms is prevalent in as high as 50% of the population in long-term care.

Bacteria can be detected with a urine dipstick test for urinary nitrite or by urinary microscopy, although bacterial culture remains the most specific and formal test (the gold standard).

Per Infectious Disease Society of America guidelines, bacteriuria can be confirmed if a single bacterial species is isolated in a concentration greater than 100,000 colony forming units per millilitre of urine in clean-catch midstream urine specimens (one for men, two consecutive specimens with the same bacterium for women). For urine collected via bladder catheterization in men and women, a single urine specimen with greater than 100,000 colony forming units of a single species per millilitre is considered diagnostic. The threshold is also 100 colony forming units of a single species per millilitre for women displaying UTI symptoms.

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