How should I treat a Serratia rubidaea catheter tunnel infection in an adult without a beta‑lactam allergy?

Treatment of Serratia rubidaea Catheter Tunnel Infection

Remove the catheter immediately and administer 7-10 days of systemic antibiotics based on susceptibility testing, with incision and drainage if there is abscess formation. 1

Immediate Management Steps

Catheter Removal is Mandatory

• Tunnel infections require catheter removal without exception – this is a non-negotiable recommendation from the Infectious Diseases Society of America guidelines for catheter-related infections. 1
• The catheter cannot be salvaged when tunnel infection is present, unlike simple exit site infections or uncomplicated bacteremia. 1
• If an abscess has formed in the tunnel tract or port pocket, perform incision and drainage at the time of catheter removal. 1

Obtain Cultures Before Starting Antibiotics

• Culture any purulent drainage from the tunnel site before initiating antimicrobial therapy. 1
• Draw blood cultures from both a peripheral vein and through the catheter (if still in place) to document bacteremia. 1
• Send the catheter tip for semiquantitative or quantitative culture after removal. 1

Antibiotic Selection for Serratia rubidaea

Empiric Therapy

• Start empiric coverage immediately with an antipseudomonal beta-lactam (ceftazidime, cefepime, or piperacillin-tazobactam) plus an aminoglycoside or fluoroquinolone while awaiting susceptibilities. 2, 3
• Serratia species harbor inducible chromosomal AmpC beta-lactamases, making them intrinsically resistant to ampicillin and first-generation cephalosporins. 4, 5

Definitive Therapy Based on Susceptibilities

• Carbapenems (imipenem or meropenem) are the most reliable agents for Serratia infections, with near-universal susceptibility. 5
• Fluoroquinolones (ciprofloxacin) demonstrate excellent activity against most Serratia strains and can be used for definitive therapy. 4, 5
• Fourth-generation cephalosporins (cefepime) are preferred over third-generation agents due to stability against AmpC beta-lactamases. 2
• Avoid third-generation cephalosporins (ceftriaxone, cefotaxime) as monotherapy due to high resistance rates and risk of resistance development during treatment. 2, 5

Duration of Antibiotic Therapy

• Administer 7-10 days of systemic antibiotics for tunnel infection without concomitant bacteremia. 1
• If bacteremia is documented, extend therapy to 10-14 days minimum. 1
• If complications develop (septic thrombosis, endocarditis, metastatic infection), treat for 4-6 weeks. 1

Post-Removal Catheter Management

Timing of New Catheter Placement

• Do not insert a new tunneled catheter until systemic antibiotics have been administered and repeat blood cultures are negative. 1, 3
• Ideally, wait until the full antibiotic course is completed and blood cultures drawn 5-10 days later remain negative. 1
• For patients requiring immediate vascular access, place a temporary non-tunneled catheter at a different anatomical site. 6

Site Selection for Replacement

• Never insert a new catheter at the same site as the infected tunnel. 6
• Choose a completely different anatomical location (e.g., if right internal jugular was infected, use left subclavian or femoral). 6

Critical Pitfalls to Avoid

Do Not Attempt Catheter Salvage

• Unlike coagulase-negative staphylococcal infections or simple exit site infections, tunnel infections cannot be treated with antibiotics alone or with antibiotic lock therapy. 1
• Attempting to preserve the catheter in tunnel infection leads to treatment failure, persistent infection, and increased mortality. 1

Monitor for Complications

• Serratia species can cause severe complications including septic thrombosis, endocarditis, and metastatic abscesses, particularly in debilitated patients. 4, 7
• Obtain repeat blood cultures 48-72 hours after catheter removal and antibiotic initiation to document clearance. 1, 3
• If fever persists beyond 72 hours despite appropriate antibiotics and catheter removal, aggressively evaluate for septic thrombosis or endocarditis with imaging studies. 1

Recognize High-Risk Patient Factors

• Serratia rubidaea is an opportunistic pathogen that primarily affects debilitated patients with underlying chronic diseases, diabetes, or those receiving broad-spectrum antibiotics. 4, 7
• These patients are at higher risk for treatment failure and complications, warranting closer monitoring. 4, 7