Asymptomatic bacteriuria is common - in older women, in people with diabetes, in anyone with a long-term catheter, where it is close to universal - and treating it does not prevent symptomatic infection, does not reduce mortality, and does select resistance. The only established exceptions are pregnancy and before an invasive urological procedure that will breach the mucosa.
The practical problem is that the culture is often sent for the wrong reason. Confusion, a fall, a smell, or cloudy urine in an older patient are not urinary symptoms, and a culture sent to explain them will frequently come back positive and will then be treated. The discipline is upstream: decide before sending whether a positive result would change management, and if the answer is no, do not send it.
When a catheterised patient does need treatment, change the catheter before or at the start of antibiotics; leaving the biofilm in place is why these infections recur. And where the indication is genuine, take the culture before the first dose, not after.
- Do not send a urine culture for confusion, falls or odour without localising urinary symptoms
- Treat asymptomatic bacteriuria only in pregnancy or before mucosa-breaching urological surgery
- Change a long-term catheter when starting treatment for a catheter-associated infection
- Take the culture before the first antibiotic dose
- Record why the culture was sent, so the result is interpreted against a question rather than in isolation
Why it matters
Most inappropriate urinary antibiotics start with a test that should not have been ordered, not with a decision to treat.
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