Serratia peritonitis is a rare but serious intra-abdominal infection caused by Serratia marcescens, a gram-negative, facultative anaerobic bacillus of the Enterobacteriaceae family. This opportunistic pathogen primarily affects immunocompromised individuals and patients undergoing peritoneal dialysis. Due to its intrinsic and acquired resistance to multiple antibiotics, early diagnosis and aggressive management are critical to improving outcomes.
Pathogenesis of Serratia Peritonitis
Serratia species, particularly S. marcescens, infiltrate the peritoneal cavity through various routes, most commonly:
- Peritoneal dialysis catheters (especially in CAPD patients)
- Gastrointestinal perforation or leakage
- Postoperative abdominal contamination
- Hematogenous spread from distant infections
Once in the peritoneal space, the bacteria initiate a robust inflammatory response, potentially leading to systemic sepsis.
Risk Factors
- Chronic peritoneal dialysis (CAPD or APD)
- Recent abdominal surgery or trauma
- Immunosuppression (HIV, chemotherapy, corticosteroids)
- Gastrointestinal perforations
- Nosocomial contamination
- Recurrent urinary tract infections or bacteremia due to Serratia
Clinical Manifestations
The presentation of Serratia peritonitis may vary, but common symptoms include:
Localized Abdominal Symptoms
- Severe abdominal pain or tenderness
- Abdominal distension
- Rebound tenderness
- Guarding or rigidity
Systemic Signs
- Fever with chills
- Nausea and vomiting
- Hypotension in severe cases
- Altered mental status in advanced infections
Diagnostic Evaluation
Laboratory Tests
- Complete blood count (CBC): Elevated WBC count with left shift
- C-reactive protein (CRP) and ESR: Raised inflammatory markers
- Peritoneal fluid analysis: Cloudy effluent, >100 WBC/µL, predominance of neutrophils
Microbiological Identification
- Peritoneal fluid culture: Definitive diagnosis via isolation of Serratia marcescens
- Blood cultures: Detect systemic spread
- Antibiotic susceptibility testing: Essential due to known resistance patterns
Imaging
- Ultrasound or CT scan: Detects abscesses, bowel perforations, or catheter malposition
Antimicrobial Therapy
Empiric Treatment
Prompt initiation of broad-spectrum antibiotics is crucial while awaiting culture results. Empiric therapy typically includes:
- Third or fourth-generation cephalosporins (e.g., cefepime)
- Carbapenems (e.g., meropenem) for multi-drug resistant strains
- Aminoglycosides (e.g., gentamicin) for synergistic bactericidal activity
Targeted Therapy
Upon culture confirmation, antibiotic therapy should be narrowed based on susceptibility. Serratia marcescens commonly resists:
- Ampicillin
- First-generation cephalosporins
- Some beta-lactams (due to AmpC beta-lactamase production)
Effective antibiotics often include:
- Cefepime
- Ciprofloxacin
- Meropenem
- Trimethoprim-sulfamethoxazole
Duration of Therapy
- Uncomplicated cases: 10–14 days
- Severe or catheter-associated cases: Up to 21 days, especially if surgery is required
Role of Surgical and Supportive Interventions
Indications for Surgical Management
- Abscess formation
- Bowel perforation
- Failure to respond to medical therapy
- Peritoneal catheter-related infection requiring removal
Supportive Care
- Intravenous fluid resuscitation
- Electrolyte correction
- Nutritional support
- Intensive care monitoring in septic patients
Serratia Peritonitis in Peritoneal Dialysis Patients
Patients undergoing CAPD or APD are particularly vulnerable. Management includes:
- Immediate intraperitoneal antibiotic administration
- Catheter removal if infection persists or recurs
- Temporary or permanent shift to hemodialysis
Complications
If untreated or inadequately managed, Serratia peritonitis can lead to:
- Septic shock
- Multi-organ failure
- Adhesions and bowel obstruction
- Chronic peritoneal dysfunction
- Recurrent or relapsing infection
Prognosis and Outcome
The prognosis largely depends on:
- Timeliness of diagnosis and therapy
- Host immunity status
- Presence of complications
- Adequacy of source control
Patients with early intervention and antibiotic sensitivity generally have favorable outcomes. Delays or resistant infections significantly increase morbidity and mortality.
Prevention Strategies
In Peritoneal Dialysis
- Strict aseptic technique during exchanges
- Regular catheter care and exit site monitoring
- Patient education on sterile technique
- Timely replacement of malfunctioning catheters
Hospital-Based Measures
- Minimizing unnecessary invasive procedures
- Strict adherence to infection control protocols
- Judicious use of broad-spectrum antibiotics
Serratia peritonitis is a critical, often hospital-acquired infection with substantial clinical impact. Prompt recognition, targeted antimicrobial therapy, and source control remain the cornerstones of effective management. High-risk groups, particularly dialysis patients, require stringent preventive care to mitigate infection risks and improve outcomes.
