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Bacteriuria

Bacteriuria is the presence of bacteria in urine.[1] Bacteriuria accompanied by symptoms is a urinary tract infection while that without is known as asymptomatic bacteriuria.[1][2] Diagnosis is by urinalysis or urine culture.[3] Escherichia coli is the most common bacterium found.[1] People without symptoms should generally not be tested for the condition.[3] Differential diagnosis include contamination.[1]

Bacteriuria

Bacteruria

Emergency medicine, infectious disease

Asymptomatic, symptomatic[1][2]

Urinalysis, urine culture[3]

Contamination[1]

Based on symptoms or risk factors[3][4]

Asymptomatic: 3% (middle aged women), up to 50% (women in nursing homes)[5]
Symptomatic: up to 10% of women a year[6][7]

If symptoms are present, treatment is generally with antibiotics.[3] Bacteriuria without symptoms generally does not require treatment.[4] Exceptions may include pregnant women, those who have had a recent kidney transplant, young children with significant vesicoureteral reflux, and those undergoing surgery of the urinary tract.[3][4]


Bacteriuria without symptoms is present in about 3% of otherwise healthy middle aged women.[5] In nursing homes rates are as high as 50% among women and 40% in men.[5] In those with a long term indwelling urinary catheter rates are 100%.[5] Up to 10% of women have a urinary tract infection in a given year and half of all women have at least one infection at some point in their lives.[6][7] There is an increased risk of asymptomatic or symptomatic bacteriuria in pregnancy due to physiological changes that occur in a pregnant woman which promotes unwanted pathogen growth in the urinary tract.[8][9][10]

Signs and symptoms[edit]

Asymptomatic[edit]

Asymptomatic bacteriuria is bacteriuria without accompanying symptoms of a urinary tract infection and is commonly caused by the bacterium Escherichia coli.[8] Other potential pathogens are Klebsiella spp., and group B streptococci.[8][10] It is more common in women, in the elderly, in residents of long-term care facilities, and in people with diabetes, bladder catheters, and spinal cord injuries.[11] People with a long-term Foley catheter always show bacteriuria. Chronic asymptomatic bacteriuria occurs in as many as 50% of the population in long-term care.[12]


There is an association between asymptomatic bacteriuria in pregnant women with low birth weight, preterm delivery, cystitis, infection of the newborn and fetus death.[8][13] [10]However, most of these studies were graded as poor quality.[8] Bacteriuria in pregnancy also increases the risk of preeclampsia.[13]

The for detecting bacteriuria is a bacterial culture which identifies the concentration of bacterial cells in the urine. The culture is usually combined with subsequent testing using biochemical methods or MALDI-TOF, which allows to identify the causal bacterial species, and antibiotic susceptibility testing. Urine culture is quantitative and very reliable, but can take at least one day to obtain a result and it is expensive.[8][14] Miniaturization of bacterial culture within dipstick format, Digital Dipstick,[15] allows bacterial detection, identification and quantification for bacteriuria within 10–12 hours at the point-of-care. Clinicians will often treat symptomatic bacteriuria based on the results of the urine dipstick test while waiting for the culture results.

gold standard

Bacteriuria can usually be detected using a test. The nitrite test detects nitrate-reducing bacteria if growing in high numbers in urine. A negative dipstick test does not exclude bacteriuria, as not all bacteria which can colonise the urinary tract are nitrate-reducing. The leukocyte esterase test indirectly detects the presence of leukocytes (white blood cells) in urine which can be associated with a urinary tract infection. In the elderly, the leukocyte esterase test is often positive even in the absence of an infection. The urine dipstick test is readily available and provides fast, but often unreliable results. Some organisms such as chlamydia and Ureaplasma urealyticum will produce a negative leukocyte esterase reaction.

urine dipstick

Microscopy can also be used to detect bacteriuria. It is rarely used in clinical routine since it requires more time and equipment and does not allow reliable identification or quantification of the causal bacterial species.