IAI Learning Objectives (Barber)

- No obvious source of infection

- Occurs via bacterial translocation (gut → blood/lymph → peritoneum)

- Common patients: cirrhosis with ascites, liver disease

- Usually monomicrobial (commonly E. coli)

- Less acute distress

- Ascitic WBC >250 (diagnostic)

- spontaneous

Primary Peritonitis

- Due to perforation or injury

- Appendicitis

- Diverticulitis

- Bowel perforation/obstruction

- Trauma

- Polymicrobial

- Mix of gram-negative + anaerobes

- Sepsis signs (tachycardia, hypotension, fever)

- Diffuse abdominal pain + guarding

Secondary Peritonitis

- Persistent/recurrent infection ≥48 hrs after treatment

- Often post-operative

- More resistant organisms (nosocomial)

- Seen in critically ill patients

Tertiary Peritonitis

- Bacteria enter peritoneal cavity

- Containment attempt

- Complement activation

- Leukocyte response

- Fluid/protein shift

- Successful containment → abscess

- Failure → diffuse peritonitis

Pathophysiology of Complicated IAIs

translocation without perforation

Primary

direct contamination (perforation, surgery, trauma)

Secondary

As GI tract progresses increase Gram-negative bacteria and increase Anaerobes

Important Trend

- Hemodynamic resuscitation

- MAP ≥65 mmHg

- Urine output ≥0.5 mL/kg/hr

- Use crystalloids

Initial Management

- Drain infection

- Paracentesis (ascites)

- Abscess drainage (IR or surgery)

- Fix underlying cause

- Surgery (e.g., perforation repair)

Source Control

- Start empiric antibiotics early

- Tailor based on Severity and Community vs. healthcare-associated

Antimicrobial Therapy

- Ertapenem

- Tigecycline

Mild-Moderate Infection Single agents

- Ceftriaxone

- cefotaxime

- + Metronidazole

Mild-Moderate Infection Combo

- Imipenem-Cilastatin

- Meropenem

- doripenem

- Piperacillin-tazobactam

Severe / High-Risk Infection Single agents

- Cefepime

- ceftazidime

- ciproflozacin

- levofloxacin

- + metronidazole

Severe / High-Risk Infection Combo

- Ampicillin-sulbactam

- Quinolones

E. coli resistance avoid

- Cefoxitin

- clindamycin

anaerobe resistance avoid

aminoglycosides

community required infections avoid

echinocandin

Antifungal

only in high-risk or healthcare-associated

Enterococcus

MRSA coverage

healthcare-associated infections

- 4–7 days if adequate source control

- Shorter durations supported (3–5 days) (STOP-IT trial)

- No antibiotics for Non-infected pancreatitis

Duration of Therapy

- Caused by disruption of normal gut flora

- Toxin A → fluid secretion, inflammation

- Toxin B → mucosal destruction

- Spores are resistant to acid + alcohol sanitizers

c diff

- First-line: Fidaxomicin

- Alternate PO vanc

- Alternate IV/PO metronidazole

Initial Episode

- Preffered: Fidaxomicin

- Alternatives: PO vancomycin

- Alternatives: PO Vancomycin, then rifaximin

- Alternatives: Bezlotoxumab + fidaxomicin or PO vancomycin

1st Recurrence

- Preffered: Fidaxomicin

- Alternatives: Fecal Microbiota Transplant (FMT)

- Alternatives: PO vancomycin

- Alternatives: PO Vancomycin, then rifaximin

- Alternatives: Bezlotoxumab + fidaxomicin or PO vancomycin

2nd recurrence

- Preferred: Bezlotoxumab + fidaxomicin

- Alternative: → Bezlotoxumab + vancomycin

Recurrence within 6 months