Spontaneous Bacterial Peritonitis (SBP)

1️⃣ What is Spontaneous Bacterial Peritonitis?

Spontaneous Bacterial Peritonitis (SBP) is an infection of ascitic fluid without an evident surgically treatable intra-abdominal source.

It most commonly occurs in:

• Cirrhosis with ascites
• Less commonly: nephrotic syndrome, heart failure, malignancy

🔴 If a perforation, abscess, or bowel ischemia is present → that is secondary peritonitis, not SBP.

2️⃣ Why Does SBP Occur? (Pathophysiology)

A. Bacterial Translocation (Core Mechanism)

Occurs in advanced cirrhosis due to:

• Increased intestinal permeability
• Small intestinal bacterial overgrowth
• Impaired local immunity
• Portal hypertension

Gut bacteria migrate:

Intestinal lumen → Mesenteric lymph nodes → Bloodstream → Ascitic fluid

B. Immune Dysfunction in Cirrhosis

Cirrhosis causes:

• Reduced complement levels
• Decreased opsonization
• Impaired neutrophil function
• Low ascitic protein (<1 g/dL = high risk)

Low protein → low opsonic activity → easier infection.

3️⃣ Microbiology

Common Organisms

 Increasing multidrug resistance in hospital-acquired SBP.

Common Contaminant (Commensal) Organisms in Paracentesis

1️⃣ Skin Flora (Most Common Source)

These are the classic contaminants:

🔹 Staphylococcus epidermidis

• Most common contaminant
• Often single bottle growth

🔹 Staphylococcus aureus

• Can be contaminant
• BUT also true pathogen
• If multiple cultures positive → treat seriously

🔹 Corynebacterium

🔹 Cutibacterium acnes

2️⃣ Environmental Organisms

These may contaminate during ICU procedures:

🔹 Bacillus species (non-anthracis)

🔹 Micrococcus species

3️⃣ Organisms That Are RARELY Simple Contaminants

If these grow, be cautious:

• Escherichia coli
• Klebsiella pneumoniae
• Enterococcus faecalis
• Acinetobacter baumannii

Gram-negative bacilli are much less likely to be simple contamination in a sterile tap.

4️⃣ Clinical Features

 SBP can be subtle or silent.

Symptoms:

• Fever
• Abdominal pain
• Diffuse tenderness
• Worsening ascites
• Altered mental status
• Hypotension
• Renal dysfunction

Exam Finding:

• Mild abdominal tenderness
• Rebound usually absent
• Guarding → think secondary peritonitis

5️⃣ Diagnosis 

Diagnostic Gold Standard = Paracentesis

🟢 ALL cirrhotic patients with ascites admitted to hospital must undergo diagnostic paracentesis.

Diagnostic Criteria

Types of SBP

✔ Treat CNNA same as SBP
❗ Bacterascites without symptoms → observe

6️⃣ How to Perform Diagnostic Paracentesis

• Preferred site: Left lower quadrant
• Use sterile technique
• Send fluid for:
• Cell count with differential
• Culture (inoculate directly into blood culture bottles at bedside)
• Albumin
• Total protein
• Gram stain (low sensitivity)

7️⃣ Differentiating SBP vs Secondary Peritonitis

Runyon’s Criteria (Suggests Secondary Peritonitis)

If ≥2 present:

Additional clues:

• Multiple organisms
• Very high PMN (>10,000)
• Lack of response to antibiotics
• Free air on imaging

 Always rule out perforation if suspected.

8️⃣ Treatment (Guideline-Based)

1️⃣ Start Antibiotics Immediately

Community-acquired SBP:

• Cefotaxime 2 g IV q8h
  OR
• Ceftriaxone 1–2 g IV daily

Duration: 5–7 days

Nosocomial / High MDR Risk:

• Piperacillin–tazobactam
  OR
• Carbapenem (meropenem) if ESBL risk
  ± Vancomycin (if MRSA risk)

2️⃣ Albumin Therapy 

Albumin reduces mortality & prevents HRS.

Indications:

• Serum creatinine >1 mg/dL
• BUN >30 mg/dL
• Bilirubin >4 mg/dL

Dose:

• Day 1 → 1.5 g/kg
• Day 3 → 1 g/kg

Mechanism:

• Prevents circulatory dysfunction
• Reduces renal failure

9️⃣ Monitoring

Repeat paracentesis at 48 hours:

• PMN should drop ≥25%
• If not → suspect resistant organism or secondary peritonitis

Monitor:

• Renal function
• Electrolytes
• Blood pressure
• Mental status

🔟 Complications

• Hepatorenal syndrome (HRS)
• Septic shock
• Recurrent SBP
• Multi-organ failure

Mortality:

• 20–30% per episode
• 70% at 1 year if no transplant

1️⃣1️⃣ SBP Prophylaxis

Who Needs Primary Prophylaxis?

Drug:

• Norfloxacin 400 mg daily
  OR
• TMP-SMX daily

Secondary Prophylaxis (After 1 Episode)

Lifetime prophylaxis until transplant:

• Norfloxacin 400 mg daily

1️⃣2️⃣ Spontaneous Fungal Peritonitis (Rare but Deadly)

Occurs in:

• ICU patients
• Long antibiotic exposure

Organism:

• Candida

High mortality
Treat with echinocandin.