urinary tract infections
Uncomplicated cystitis: nitrofurantoin or TMP-SMX (avoid fluoroquinolones). Pyelonephritis and complicated UTI: culture first; ceftriaxone inpatient; 7 days total for most patients who improve (5–7 days if fluoroquinolone) per IDSA 2025 — including men and Gram-negative bacteraemia. ESBL cover only with prior ESBL or septic shock. Do not treat asymptomatic bacteriuria outside pregnancy and pre-urological procedures.
- first-line: nitrofurantoin monohydrate/macrocrystals 100 mg PO BID × 5 days (avoid if CrCl <30–40 mL/min)
- alternative: TMP-SMX DS PO BID × 3 days (if local E. coli resistance <20%)
- alternatives: pivmecillinam, or fosfomycin 3 g PO single dose (lower cure rates)
- avoid fluoroquinolones for cystitis
- no culture needed for classic cystitis in non-pregnant women
- men: 7 days (TMP-SMX, ciprofloxacin, or nitrofurantoin if no prostatic involvement)
- urine culture before antibiotics — always
- outpatient: ciprofloxacin 500 mg PO BID × 7 days, or TMP-SMX DS PO BID × 7 days if susceptible
- local E. coli FQ resistance >10% (common): one dose ceftriaxone or gentamicin IV first, then PO per culture
- inpatient first-line: ceftriaxone 1–2 g IV q24h
- if male, catheter, or haemodynamic instability: add ampicillin 2 g IV q6h (Enterococcus)
- if β-lactams must be avoided: gentamicin 7 mg/kg IV q24h or ciprofloxacin — see penicillin allergy
- if known ESBL, ESBL in urine within 6 months, or septic shock: ertapenem 1 g IV q24h (meropenem if shock)
- PO step-down per susceptibilities when afebrile and haemodynamically stable
- duration: 7 days total if improving (5–7 days if fluoroquinolone)
E. coli TMP-SMX resistance exceeds 20% in many Canadian centres, and fluoroquinolone resistance is rising — both matter for empiric oral choices.
classification
| type | definition | examples |
|---|---|---|
| uncomplicated cystitis | lower UTI in a non-pregnant woman with normal urinary tract | dysuria, frequency, urgency |
| complicated UTI (IDSA 2025) | UTI with systemic features, renal parenchymal involvement, upper-tract obstruction, or an indwelling device | pyelonephritis, fever/rigors/flank pain, obstructing stone, catheter, nephrostomy, ureteric stent |
IDSA 2025: male sex, pregnancy, diabetes, immunocompromise, or a urological abnormality alone do not make a UTI complicated — cystitis in these groups is still cystitis (though men need 7 days).
when to culture
- not needed: classic uncomplicated cystitis in non-pregnant women
- always culture: pyelonephritis, complicated UTI, male UTI, pregnancy, treatment failure, recurrent UTI, recent antibiotics, catheter-associated
empiric therapy — detail
uncomplicated cystitis
| agent | dose | duration | notes |
|---|---|---|---|
| nitrofurantoin monohydrate/macrocrystals | 100 mg PO BID | 5 days | first-line; not for pyelonephritis; avoid if CrCl <30–40 mL/min |
| TMP-SMX | DS (160/800) PO BID | 3 days | if local resistance <20%; avoid 1st trimester and at term |
| pivmecillinam | 400 mg PO BID | 3–5 days | available in Canada |
| fosfomycin | 3 g PO | single dose | lower efficacy; useful for resistant organisms |
Pregnancy (treat 7 days; culture-directed): amoxicillin-clavulanate, nitrofurantoin (avoid ≥36 weeks), or TMP-SMX (avoid 1st trimester and at term).
acute pyelonephritis / complicated UTI
Outpatient (mild, tolerating PO, reliable follow-up):
- ciprofloxacin 500 mg PO BID × 7 days — Sandberg (2012): 7 days non-inferior to 14 days
- local E. coli fluoroquinolone resistance >10% (IDSA threshold; exceeded in many Canadian centres) → give one parenteral dose of ceftriaxone or a 24-h aminoglycoside dose before the oral fluoroquinolone
- TMP-SMX DS PO BID × 7 days if susceptible — give one dose of ceftriaxone 1–2 g IV/IM first if used before susceptibilities return
Inpatient:
- without sepsis: 3rd/4th-generation cephalosporin, piperacillin-tazobactam, or fluoroquinolone — not carbapenems (IDSA 2025)
- ceftriaxone 1–2 g IV q24h ± ampicillin (men, catheter, instability)
- ESBL risk: ertapenem 1 g IV q24h; septic shock with ESBL risk → meropenem 1 g IV q8h
- with sepsis: carbapenem also acceptable empirically
- switch to oral for the remainder once afebrile and stable, per susceptibilities (IDSA 2025 favours PO over continued IV)
catheter-associated
- remove or replace the catheter — most effective single intervention
- culture from the new catheter before antibiotics
- treat as complicated UTI; 7 days if prompt response
penicillin allergy
- ceftriaxone shares no side chain with penicillins → usable after most penicillin reactions, including prior anaphylaxis (except near-fatal within 10 years)
- avoid all β-lactams only after SCAR, serum sickness, AIN, or haemolysis → gentamicin or ciprofloxacin
- carbapenems: negligible cross-reactivity with penicillins
- full framework: penicillin allergy
duration
| scenario | duration |
|---|---|
| uncomplicated cystitis — nitrofurantoin | 5 days |
| uncomplicated cystitis — TMP-SMX | 3 days |
| cystitis in men | 7 days — Drekonja (2021): 7 days non-inferior to 14 in afebrile men |
| pyelonephritis / complicated UTI, improving | 7 days (5–7 days if fluoroquinolone) |
| complicated UTI + Gram-negative bacteraemia, improving | 7 days |
| acute bacterial prostatitis | traditionally 2–4 weeks (FQ or TMP-SMX); IDSA 2025: 10–14 days may suffice, limited evidence |
| chronic bacterial prostatitis | fluoroquinolone 4–6 weeks (TMP-SMX longer if FQ not possible) |
| slow response | look for obstruction, abscess, prostatitis → longer course |
asymptomatic bacteriuria
Positive culture without urinary symptoms does not need antibiotics in non-pregnant adults — including elderly, catheterised, diabetic, and spinal cord injury patients. Treatment does not reduce symptomatic episodes or mortality and drives resistance.
Screen and treat ASB only in:
- pregnancy — screen once in early pregnancy
- before urological procedures with anticipated mucosal bleeding
Pyuria does not distinguish ASB from UTI. Delirium without fever or urinary symptoms is not a UTI in a non-catheterised patient.
traps
- cloudy/malodorous urine is not a UTI — do not culture or treat without symptoms
- confusion in an elderly patient with a positive urine culture → search for another cause first
- nitrofurantoin and fosfomycin do not achieve renal tissue levels → never for pyelonephritis
- men: nitrofurantoin is inappropriate if prostatic involvement suspected; recurrent “UTI” in a man → evaluate for prostatitis/urology referral
- catheter bacteriuria accrues ~3–7% per day and is near-universal by 1 month — treat only if symptomatic
- 14 days is no longer default for men or bacteraemia — 7 days if improving
Key references
+3 more sources
- resourceChoosing Wisely Canada. Don't treat asymptomatic bacteriuria in non-pregnant adults.