What prophylactic antibiotic regimen is recommended for a patient with normal renal function undergoing Transrectal Ultrasound (TRUS) biopsy?

Prophylactic Antibiotic for TRUS Biopsy

Direct Answer

For patients with normal renal function undergoing transrectal ultrasound (TRUS) prostate biopsy, the optimal approach is targeted prophylaxis based on rectal swab culture when feasible; when not feasible, use fluoroquinolone alternatives including fosfomycin trometamol (3g before and 3g at 24-48 hours post-biopsy), ceftriaxone (1g IM), or aminoglycosides (gentamicin 3mg/kg IV). 1

Evidence-Based Antibiotic Selection Algorithm

First-Line Approach: Targeted Prophylaxis

• Obtain rectal swab culture before biopsy and provide antibiotics based on susceptibility results when this approach is available, as recommended by the European Association of Urology 2024 guidelines. 1
• This strategy addresses the critical problem of fluoroquinolone resistance, which now affects 62-91% of post-TRUS biopsy E. coli bloodstream infections. 2

When Targeted Prophylaxis Is Not Feasible

Option 1: Fosfomycin Trometamol

• Dose: 3g orally before biopsy, then 3g at 24-48 hours post-biopsy 1
• This two-dose regimen provides coverage against fluoroquinolone-resistant organisms 1
• Caveat: Check local availability, as this indication has been withdrawn in some countries 1

Option 2: Cephalosporins

• Ceftriaxone 1g intramuscularly as single dose 1
• Alternative: Cefixime 400mg orally for 3 days starting 24 hours before biopsy 1

Option 3: Aminoglycosides

• Gentamicin 3mg/kg intravenously or amikacin 15mg/kg intramuscularly 1
• Important: Gentamicin alone as monotherapy showed significantly higher infection rates (P=0.004) compared to combination regimens 3

Historical Standard (Now Problematic)

Ciprofloxacin was historically the standard prophylactic antibiotic 4, 1, with large RCTs demonstrating efficacy in reducing bacteriuria. 4 However:

• Fluoroquinolone resistance has rendered single-agent ciprofloxacin significantly less effective, with infection rates of 88-91% among E. coli isolates showing fluoroquinolone resistance 3, 2
• E. coli sequence type 131 (ST131), a multidrug-resistant clone, accounts for 41% of post-TRUS biopsy infections 2
• Ciprofloxacin monotherapy was associated with significantly more infections than combination regimens (P=0.014) 3

Duration of Prophylaxis

Single-dose or one-day regimens are as effective as three-day regimens for standard prophylaxis. 4

• Multiple RCTs confirm equivalence between single-dose and three-day dosing 4, 5, 6
• A French multicenter RCT of 322 patients showed no significant difference in infection rates: 0.75% with single-dose versus 0.69% with three-day ciprofloxacin (P>0.9) 5
• A Canadian RCT of 363 patients demonstrated identical sepsis rates (0.55%) between one-day and three-day regimens 6

Exception: Fosfomycin requires the specific two-dose regimen (pre- and post-biopsy) 1

Combination Therapy Considerations

In high-risk settings or areas with high fluoroquinolone resistance, combination regimens significantly reduce infection rates:

• Any combination regimen showed significantly lower infection rates than any single-agent regimen (OR 4.0; 95% CI 1.47-10.85; P=0.004) 3
• A Chinese RCT demonstrated that amoxicillin-clavulanate + ciprofloxacin reduced infections to 0.53% versus 3.91% with amoxicillin-clavulanate alone 7
• However, this approach contravenes antibiotic stewardship principles and should be reserved for documented high-risk situations 1

Critical Clinical Context

Prophylaxis is indicated in all patients undergoing TRUS biopsy (Level of Evidence: Ib) 4

• Without prophylaxis, post-biopsy infection rates are unacceptably high 4
• Post-TRUS biopsy E. coli bacteremia patients are twice as likely to require ICU admission (25% vs 12%) compared to other community-onset E. coli bacteremia 2
• 36% of post-TRUS biopsy patients did not receive active empirical therapy when fluoroquinolones were used in high-resistance settings 2

Common Pitfalls to Avoid

• Do not rely solely on ciprofloxacin in areas with known fluoroquinolone resistance >10%, as treatment failure is common 3, 2
• Do not use gentamicin as monotherapy, as it shows significantly higher infection rates than combination regimens 3
• Do not extend prophylaxis beyond necessary duration, as single-dose regimens are equally effective for most patients 4, 5, 6
• Do not assume diabetes, immunosuppression, or recent hospitalization predict infection risk in the context of resistant organisms—the primary driver is antibiotic resistance patterns 3