Asymptomatic bacteriuria occurs when the patient has no symptoms, the urine microscopy is normal (no red cells, no white cells and no nitrites present) and yet the urine culture is positive with a bacterial growth of over 108 colony forming units/L. It occurs most commonly in the elderly, those with diabetes, pregnant women and those with obstruction to urination. It is very common, generally does not require treatment and is usually not related to complications.
However, certain risk groups do need screening for asymptomatic bacteriuria and antibiotics to prevent problems occurring. Urine microscopy and culture should be arranged in the first trimester of pregnancy routinely.
Pregnant women at any gestation should be treated with antibiotics if bacteriuria is present as the increasingly gravid uterus affects ureteric drainage and bladder emptying, increasing the risk of urinary infections. Urine infections in pregnancy are associated with an increased risk of pyelonephritis, premature labour and low birth weight.
Men who are to have urinary tract surgery should be investigated and treated for asymptomatic bacteriuria before the procedure.
There should be a low threshold for dipstick urinalysis (plus or minus urine microscopy and culture) in the elderly, post-menopausal women, those who have had recurrent urinary tract infections, people with diabetes, those with indwelling catheters, the immobile, those with spinal cord damage and the immunosuppressed, as many such individuals may have urine infections in the absence of typical symptoms. However, if asymptomatic bacteriuria is discovered, it does not require treatment. This is because treatment has not been proven to reduce the incidence of subsequent urinary tract infections, although it is well known that these groups are at increased risk of these. There is ample evidence though that treating asymptomatic bacteriuria in these groups results in antibiotic resistance and that this development persists long-term.
1. NPS Medicinewise, Decisions and management for asymptomatic bacteriuria
2. Cai, T. et al. Asymptomatic bacteriuria treatment is associated with a higher prevalence of antibiotic resistant strains in women with urinary tract infections, Clinical Infectious Diseases 2015; 61:1662-3