What is the recommended treatment for an asymptomatic patient with 100,000 Colony-Forming Units per milliliter (CFU/mL) of gram-positive cocci in the urine, found on a preoperative Urinalysis (U/A), prior to Total Knee Replacement (TKR) surgery?

Management of Asymptomatic Bacteriuria Before Total Knee Replacement

Direct Recommendation

Do not treat this asymptomatic bacteriuria prior to total knee replacement surgery. 1, 2

Evidence-Based Rationale

Orthopedic Surgery Does Not Require ASB Treatment

• The Infectious Diseases Society of America (IDSA) strongly recommends against screening for or treating asymptomatic bacteriuria before arthroplasty surgery, including total knee replacement. 1

• The European Association of Urology 2024 guidelines explicitly state: "Do not screen or treat asymptomatic bacteriuria in patients before arthroplasty surgery" with a strong recommendation. 1

• This applies even though you have already identified the bacteriuria—treatment is not indicated regardless of the bacterial count or organism type. 2

Why Treatment Is Not Beneficial

• Prosthetic joint infections following arthroplasty are caused by skin flora (particularly biofilm-producing staphylococci), not urinary pathogens. 1

• A systematic review of 3,267 arthroplasty patients found that organisms responsible for prosthetic joint infections were different from those cultured in preoperative urine, making a direct causal relationship "extremely unlikely." 3

• There is no evidence that treating ASB reduces surgical site infections or mortality in orthopedic procedures. 2, 3

Harms of Unnecessary Treatment

• Treating asymptomatic bacteriuria when not indicated causes:
  • Increased antimicrobial resistance 2, 3
  • Risk of Clostridioides difficile infection 2
  • Drug adverse effects 2
  • Increased healthcare costs 2
  • Selection for more resistant reinfecting organisms 1

What You Should Do Instead

Standard Perioperative Prophylaxis Only

• Administer standard surgical antibiotic prophylaxis (typically cefazolin or cefuroxime, with or without gentamicin) 30-60 minutes before incision, as you would for any TKR patient. 1, 4

• This prophylaxis targets skin flora (gram-positive cocci from the surgical site), not urinary organisms. 4, 5

• Do not modify or extend the prophylaxis regimen based on the urine culture results. 2

Monitor for Symptomatic UTI

• Only treat if the patient develops UTI symptoms (dysuria, frequency, urgency, suprapubic pain, or fever without another source). 2

• Pyuria accompanying asymptomatic bacteriuria is not an indication for treatment in this surgical context. 2

Critical Distinction: When ASB Treatment IS Required

This recommendation is specific to non-urologic surgery. Treatment would be mandatory if this were:

• Endoscopic urologic procedures breaching the mucosa (TURP, TURBT, ureteroscopy, percutaneous stone surgery)—where untreated ASB carries 13% sepsis risk. 1, 2

• In those cases, preoperative urine culture with targeted short-course antibiotics (1-2 doses) would be essential. 2

Common Pitfall to Avoid

Do not treat the gram-positive cocci simply because they are present or because the patient has a prosthetic device being implanted. The evidence clearly shows this practice increases harm without reducing infection risk in arthroplasty patients. 1, 2, 3