Should an elderly woman with asymptomatic Pseudomonas aeruginosa bacteriuria, with a colony count of 10^3 CFU/mL in her catheter, continue taking Zinnat (Cefuroxime)?

Management of Asymptomatic Pseudomonas Bacteriuria in a Catheterized Elderly Woman

Stop the Zinnat (cefuroxime) immediately and do not treat this asymptomatic bacteriuria. The current antibiotic is inappropriate for Pseudomonas aeruginosa and treating asymptomatic catheter-associated bacteriuria provides no clinical benefit while promoting antimicrobial resistance.

Rationale for No Treatment

Screening for and treatment of catheter-associated asymptomatic bacteriuria (CA-ASB) are not recommended in patients with indwelling catheters, including elderly patients. 1 This is a Grade A-I recommendation from the Infectious Diseases Society of America, representing the highest level of evidence. 1

Key Supporting Evidence

• Catheterized patients have virtually 100% bacteriuria when long-term catheters are in place, making bacteriuria an expected finding rather than a pathologic one requiring treatment. 1

• Treatment of CA-ASB does not reduce subsequent symptomatic UTIs or improve mortality in catheterized patients, whether short-term or long-term catheterization. 1

• Elderly institutionalized patients should not be screened or treated for asymptomatic bacteriuria (Grade A-I recommendation). 1 This applies regardless of the organism isolated, including Pseudomonas aeruginosa.

• Treating asymptomatic bacteriuria increases antimicrobial resistance without clinical benefit, as demonstrated in studies showing 47% of reinfecting organisms became highly resistant after treatment versus 26% in untreated patients. 1

Why Cefuroxime (Zinnat) is Inappropriate

Cefuroxime has no activity against Pseudomonas aeruginosa. 2 Even if treatment were indicated (which it is not), this antibiotic would be ineffective. The drug review explicitly states cefuroxime "has no effect against infections caused by Pseudomonas aeruginosa." 2

The Exception: When to Consider Treatment

The only scenario where treatment might be considered is if the catheter is removed and bacteriuria persists 48 hours post-removal in a woman. 1 This is a Grade B-I recommendation. 1 In that specific circumstance:

• Wait 48 hours after catheter removal
• Reculture the urine
• If bacteriuria persists AND the patient remains asymptomatic, treatment may be considered to reduce subsequent symptomatic UTI risk 3
• However, this remains optional, not mandatory

Appropriate Follow-Up Strategy

While Catheter Remains In Place:

• Do not obtain surveillance urine cultures unless the patient develops symptoms suggesting UTI (fever, altered mental status, new-onset suprapubic pain, costovertebral angle tenderness). 1, 3

• Cloudy or malodorous urine alone should not trigger treatment in catheterized elderly patients, as these findings do not indicate symptomatic infection. 1

If Catheter is Removed:

• Consider a single urine culture 48 hours after catheter removal if you are contemplating treatment per the exception above. 1, 3

• If bacteriuria persists at 48 hours post-removal and you choose to treat, appropriate anti-pseudomonal agents would include fluoroquinolones (if susceptible), ceftazidime, cefepime, piperacillin-tazobactam, or carbapenems—but NOT cefuroxime. 4

Critical Pitfalls to Avoid

• Do not treat based on colony count alone. The 10³ CFU/mL you report is actually below the diagnostic threshold for catheterized patients (which is ≥10² CFU/mL for a single catheterized specimen), but this is irrelevant since the patient is asymptomatic. 1

• Do not continue ineffective antibiotics. Cefuroxime will not eradicate Pseudomonas and only promotes resistance. 2

• Do not confuse asymptomatic bacteriuria with symptomatic UTI. In elderly patients, careful clinical assessment is essential, as cognitive impairment may complicate symptom evaluation. 1

• Avoid routine prophylactic antimicrobials at catheter placement, removal, or replacement, as this promotes resistance without reducing CA-UTI rates. 3, 5

Summary Action Plan

1. Discontinue cefuroxime immediately 2
2. Do not initiate alternative antibiotics while the patient remains asymptomatic and catheterized 1
3. Monitor clinically for symptoms of infection (fever, altered mental status, hemodynamic instability) 1
4. Only obtain urine cultures if symptoms develop or 48 hours after catheter removal if considering treatment 1, 3
5. If catheter removal is planned and bacteriuria persists 48 hours later, treatment becomes optional but not mandatory 1