A positive urine culture without urinary symptoms does not need an antibiotic in almost anyone. Treating it does not reduce symptomatic infection, does not prevent renal damage, and reliably selects resistance, causes Clostridioides difficile and produces adverse drug reactions. The two established exceptions are pregnancy and a patient about to undergo a urological procedure that will breach the mucosa.
The traps are the borderline cases. Cloudy or strong-smelling urine is not a symptom. An indwelling catheter will always grow something and should not be cultured without clinical features of infection. Delirium in an older patient with a positive culture and no urinary symptoms or fever is far more often something else, and treating the urine delays finding it. And a positive dipstick in an asymptomatic patient is a reason not to have sent the dipstick.
The practical fix is at the point of ordering. Ask what the result will change before sending the sample, and where a culture has already come back positive in a patient with no symptoms, write in the notes why it is not being treated — otherwise the next clinician will treat it.
- Do not treat a positive culture in an asymptomatic patient outside pregnancy or pre-procedural prophylaxis.
- Do not culture a catheter specimen without clinical features of infection.
- Cloudy or malodorous urine is not a symptom of infection.
- In delirium with no urinary symptoms or fever, keep looking for another cause.
- Record in the notes why an untreated positive culture is being left alone.
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