What is the appropriate management of a urinary tract infection caused by Corynebacterium striatum in a 72‑year‑old woman with a urinary catheter and comorbidities?

Management of Corynebacterium striatum UTI in a 72-Year-Old Female

Immediate Clinical Assessment Required

First, confirm this is a true infection rather than asymptomatic bacteriuria or contamination—treatment should only be initiated if the patient has systemic signs (fever >37.8°C, rigors, or clear delirium) OR recent-onset dysuria with urinary frequency, urgency, or costovertebral angle tenderness. 1

Key Diagnostic Criteria for Elderly Patients

• Do NOT treat based solely on positive urine culture if the patient lacks specific urinary symptoms or systemic signs, as asymptomatic bacteriuria is present in 15-50% of elderly catheterized patients and treatment does not improve outcomes 1, 2, 3
• Atypical presentations in this age group include new confusion, functional decline, falls, or fatigue rather than classic dysuria 1, 2
• Negative nitrite and leukocyte esterase on dipstick strongly suggests absence of true UTI 1, 2
• Critical distinction: Nonspecific symptoms alone (cloudy urine, urine odor, nocturia, malaise, weakness) do NOT warrant antibiotic treatment without systemic signs or specific urinary symptoms 1

Pathogen-Specific Considerations for C. striatum

C. striatum is an emerging nosocomial pathogen that was historically dismissed as a contaminant but is now recognized as clinically significant, particularly in patients with:

• Indwelling catheters or medical devices 4, 5, 6
• Immunocompromise or comorbidities 4, 5
• Previous antibiotic exposure 5

Evidence supporting true infection (not contamination) includes: pure growth on culture, presence of Gram-positive rods on direct Gram stain with leukocyte reaction, and clinical signs of infection 5. The organism is frequently multidrug-resistant, with vancomycin being the most reliable agent 4, 5.

Treatment Algorithm

Step 1: Catheter Management (If Applicable)

If the catheter has been in place ≥2 weeks and is still indicated, replace it before initiating antimicrobial therapy to hasten symptom resolution and reduce risk of treatment failure 1. Obtain urine culture from the freshly placed catheter prior to antibiotics, as specimens from catheters with established biofilm may not accurately reflect bladder infection 1.

If the catheter can be removed, do so immediately 1.

Step 2: Antimicrobial Selection

Vancomycin is the treatment of choice for C. striatum UTI, as virtually all strains demonstrate multidrug resistance but remain universally susceptible to vancomycin 4, 5.

Recommended Regimen:

• Vancomycin 1g IV every 5 days for 1 month has demonstrated successful outcomes in catheter-associated C. striatum infections 5
• For severe infections or bacteremia: standard vancomycin dosing (15-20 mg/kg IV every 8-12 hours) with dose adjustment for renal function and trough monitoring

Important Considerations:

• Obtain antimicrobial susceptibility testing on all C. striatum isolates, as resistance patterns vary 4, 5
• Oral antibiotics typically fail for C. striatum infections 5
• Consider infectious disease consultation given the unusual pathogen and likely multidrug resistance 4

Step 3: Treatment Duration

For catheter-associated UTI with prompt symptom resolution: 7 days of appropriate antimicrobial therapy 1. For delayed response or complicated infection: 10-14 days 1.

For catheter-associated infections specifically involving C. striatum with device retention, longer courses (up to 1 month) may be necessary based on clinical response 5.

Critical Pitfalls to Avoid

• Do not dismiss C. striatum as a contaminant when isolated in pure culture from a catheterized patient with clinical signs of infection 4, 5, 7
• Do not use empiric oral antibiotics (fosfomycin, nitrofurantoin, trimethoprim-sulfamethoxazole, fluoroquinolones) for confirmed C. striatum, as resistance is common 4, 5
• Do not treat asymptomatic bacteriuria in catheterized patients, even with unusual organisms—this increases antimicrobial resistance without clinical benefit 1, 2, 3
• Do not fail to replace long-term catheters (≥2 weeks in place) before treatment, as this significantly impairs clinical response 1

Monitoring and Follow-Up

• Assess clinical response within 48-72 hours of initiating therapy 8
• If the patient remains catheterized, expect that bacteriuria will likely recur after treatment completion—this does NOT require retreatment unless symptomatic 1
• Review all medications for potential drug interactions and nephrotoxic agents, particularly given vancomycin use 8, 2
• Calculate creatinine clearance for appropriate vancomycin dosing, as renal function declines approximately 40% by age 70 8

Special Considerations for Comorbid Elderly Patients

Given this patient's age and likely comorbidities 1:

• Carefully assess polypharmacy concerns and potential drug interactions 1, 8
• Monitor for atypical adverse effects that may present as confusion or functional decline 3
• Consider whether underlying urological abnormalities or functional issues are contributing to infection risk 3