Bacteriuria
Other names	Bacteruria
Multiple rod-shaped bacteria shown between the largerwhite blood cells at urinary microscopy from a person withurinary tract infection.
Specialty	Emergency medicine,infectious disease
Types	Asymptomatic,symptomatic[1][2]
Diagnostic method	Urinalysis,urine culture[3]
Differential diagnosis	Contamination[1]
Treatment	Based on symptoms or risk factors[3][4]
Frequency	Asymptomatic: 3% (middle aged women), up to 50% (women in nursing homes)[5] Symptomatic: up to 10% of women a year[6][7]

Bacteriuria is the presence ofbacteria inurine.^[1] Bacteriuria accompanied by symptoms is aurinary tract infection while that without is known as asymptomatic bacteriuria.^[1][2] Diagnosis is byurinalysis 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 includecontamination.^[1]

If symptoms are present, treatment is generally withantibiotics.^[3] Bacteriuria without symptoms generally does not require treatment.^[4] Exceptions may includepregnant women, those who have had a recentkidney transplant, young children with significantvesicoureteral reflux, and those undergoing surgery of theurinary tract.^[3][4]

Bacteriuria without symptoms is present in about 3% of otherwise healthy middle aged women.^[5] Innursing homes rates are as high as 50% among women and 40% in men.^[5] In those with a long termindwelling 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]

Asymptomatic bacteriuria is bacteriuria without accompanying symptoms of a urinary tract infection and is commonly caused by the bacteriumEscherichia coli.^[8] Other potential pathogens areKlebsiella 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-termFoley 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 ofpreeclampsia.^[13]

Symptomatic bacteriuria is bacteriuria with the accompanying symptoms of aurinary tract infection (such as frequent urination, painful urination, fever, back pain, abdominal pain and blood in the urine) and includespyelonephritis orcystitis.^[11] The most common cause of urinary tract infections isEscherichia coli.^{[citation needed]}

Testing for bacteriuria is usually performed in people with symptoms of a urinary tract infection. Certain populations that cannot feel or express symptoms of infection are also tested when showing nonspecific symptoms. For example, confusion or other changes in behaviour can be a sign of an infection in the elderly. Screening for asymptomatic bacteriuria in pregnancy is a common routine in many countries, but controversial.^{[citation needed]}

• Thegold standard for detecting bacteriuria is abacterial culture which identifies the concentration of bacterial cells in the urine. The culture is usually combined with subsequent testing using biochemical methods orMALDI-TOF, which allows to identify thecausal^{[citation needed]} bacterial species, andantibiotic 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 thepoint-of-care. Clinicians will often treat symptomatic bacteriuria based on the results of theurine dipstick test while waiting for the culture results.^{[citation needed]}
• Bacteriuria can usually be detected using aurine dipstick test. Thenitrite 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. Theleukocyte 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.^{[citation needed]} Theurine dipstick test is readily available and provides fast, but often unreliable results. Some organisms such as chlamydia andUreaplasma urealyticum will produce a negative leukocyte esterase reaction.
• 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.^{[citation needed]}

Bacteriuria is assumed if a single bacterial species is isolated in a concentration greater than 100,000colony forming units per millilitre of urine in clean-catch midstream urine specimens.^[16] In urine samples obtained from women, there is a risk for bacterial contamination from the vaginal flora. Therefore, in research, usually a second specimen is analysed to confirm asymptomatic bacteriuria in 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.^[16] The threshold for women displaying UTI symptoms can be as low as 100 colony forming units of a single species per millilitre. However, bacteria below a threshold of 10000 colony forming units per millilitre are usually reported as "no growth" by clinical laboratories.^[17][18]

Using special techniques certainnon-disease causing bacteria have also been found in the urine of healthy people.^[19] These are part of theresident microbiota.^[19]

Although controversial, many countries including the United States recommend a one time screening for bacteriuria during mid pregnancy.^[20][21] The screening method is byurine culture.^[21] Screening non-pregnant adults is recommended against by theUnited States Preventive Task Force.^[21]

The decision to treat bacteriuria depends on the presence of accompanying symptoms andcomorbidities.

Asymptomatic bacteriuria generally does not require treatment.^[4] Exceptions include those undergoing surgery of the urinary tract, children withvesicoureteral reflux or others with structural abnormalities of the urinary tract.^[4][22] In many countries, regional guidelines recommend treatment of pregnant women.^[8]

There is no indication to treat asymptomatic bacteriuria in diabetics, renal transplant recipients, and in those with spinal cord injuries.^[23]

The overuse of antibiotics to treat asymptomatic bacteriuria has many adverse effects^[24] such as an increased risk of diarrhea, the spread ofantimicrobial resistance, and infection due toClostridioides difficile.

Symptomatic bacteriuria is synonymous withurinary tract infection and typically treated withantibiotics. Common choices includenitrofurantoin andtrimethoprim/sulfamethoxazole.^{[citation needed]}

• Bacteria and humans
• Abnormal clinical and laboratory findings for urine

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