Catheter-Associated Urinary Tract Infections

CAUTI: Definition & Epidemiology - The Bladder Invader

• Definition: UTI in patient with indwelling urinary catheter (IUC) for > 2 calendar days (or day before event).
• Criteria: ≥1 symptom (fever, suprapubic/CVA tenderness, urgency, frequency, dysuria) + positive urine culture (≥$10^5$ CFU/mL, ≤2 species).
• Epidemiology:
  • Most common HAI; accounts for ~70-80% of nosocomial UTIs.
  • Incidence: 3-7% per day of catheterization.
  • Key risk factor: Duration of catheterization.
  • Others: Female sex, older age, diabetes, improper catheter care.

⭐ CAUTI is the most common healthcare-associated infection worldwide, contributing significantly to morbidity and healthcare costs.

CAUTI: Pathogenesis & Microbiology - Biofilm Bad Boys

• Pathogenesis: Primarily via biofilm formation on catheter surfaces.
  • Sources: Endogenous (periurethral, rectal flora) or exogenous (HCW hands, equipment).
  • Entry Routes:
    • Extraluminal: Migration along catheter's external surface (early, common).
    • Intraluminal: Contamination of lumen/drainage bag, reflux (later, outbreaks).
• Biofilm Formation Steps:

• Microbiology - The "Biofilm Bad Boys":
  • Gram-Negative Rods (Most Common):
    • Escherichia coli (UPEC strains)
    • Klebsiella pneumoniae
    • Pseudomonas aeruginosa (strong biofilm producer)
    • Proteus mirabilis (urease → ↑pH, stones)
  • Gram-Positive Cocci:
    • Enterococcus spp. (e.g., E. faecalis)
  • Yeast:
    • Candida spp. (esp. with prolonged use/antibiotics)

⭐ Biofilm formation is the hallmark of CAUTI pathogenesis, rendering bacteria highly resistant to antibiotics and host immune responses.

CAUTI: Clinical Features & Diagnosis - Spotting the Signs

• Clinical Presentation:
  • Localized: Dysuria, urgency, frequency, suprapubic tenderness, flank pain (pyelonephritis).
  • Systemic: Fever (>38°C), rigors, altered mental status (esp. elderly), lethargy.
  • Catheter-specific: Purulent discharge at insertion site, catheter blockage.
  • ⚠️ Cloudy/foul-smelling urine alone is NOT diagnostic of CAUTI.
• Diagnostic Criteria:
  • Presence of ≥1 sign/symptom of UTI (see above).
  • No other identified source of infection.
  • Significant bacteriuria:
    • Urinalysis: Pyuria (WBC ≥10/µL or +Leukocyte Esterase), Nitrites (variable).
    • Urine Culture (properly collected specimen): ≥10^3 CFU/mL of ≥1 bacterial species.

⭐ In spinal cord injury patients, new-onset fever, ↑spasticity, or autonomic dysreflexia may be the only CAUTI signs.

CAUTI: Management & Prevention - The Counter Attack

Management Strategy:

• Diagnosis: Symptoms (fever, dysuria, urgency, suprapubic pain) + Urine culture (≥$10^3$ CFU/mL with pyuria from catheterized patient).
• Catheter Action: Remove or replace promptly. Essential step.
• Antibiotics:
  • Tailor to Culture & Sensitivity (C&S).
  • Duration: 7 days (prompt resolution); 10-14 days (delayed/severe/bacteremia).
• Asymptomatic Bacteriuria (ASB): Generally, do NOT treat in catheterized patients.

Prevention: Key Bundle (📌 "CARES")

• Catheter: Use only when strictly indicated; remove ASAP.
• Aseptic insertion by trained personnel; maintain meticulously.
• Regular review of catheter necessity (daily).
• Ensure closed, sterile drainage system; unobstructed flow, bag below bladder.
• Secure catheter properly; hand hygiene always.

⭐ The single most effective strategy to prevent CAUTI is to limit the use and duration of indwelling urinary catheters.

High‑Yield Points - ⚡ Biggest Takeaways

• CAUTI is the most common hospital-acquired infection.
• Single most important risk factor: Prolonged duration of catheterization.
• Predominant pathogen: Escherichia coli; also Klebsiella, Proteus, Pseudomonas, Enterococcus, Candida.
• Biofilm formation on catheter surfaces is key to pathogenesis and persistence.
• Diagnosis: Clinical symptoms + Pyuria + Significant bacteriuria (≥10³ CFU/mL from catheter specimen).
• Prevention: Aseptic insertion, closed drainage system, prompt catheter removal.
• Asymptomatic bacteriuria in catheterized patients: generally not screened for or treated.