Intra-abdomnial

Intra-abdominal Infection Classification 

Uncomplicated (Surgical OR Medical Management)

• Contained in the wall or abdominal organ, inflammation without anatomical disruption

  • Acute appendicitis, cholecystitis, diverticulittis 

Complicated (Surgical AND Medical Management) 

• Extends beyond the hollow viscous/organ; perforation, abscesses

  • Abscess, peritonits, reputed appendix 

Uncomplicated IAI…

1. Acute Appendicitis; surgical removal needed peri-operative OBX

   1. Stop abx within 24 hours of removal 

2. Acute Cholecystitis; surugal removal 

   1. Stop abx within 24 hours

3. Uncom. Diverticulitis inflammation WITHOUT perforation/abscess

   1. May need full ORAL abx course 7-10 days

Microbiology of IAI

1. Gram-positives 

   1. All patients; Strepococci

   2. At risk patients; Strep, Enterococci, MRSA

2. Gram-negatives

   1. All patients; Enterobacterales

   2. At risk: Enterobactearles, Pseudomonas, MDR Gram-negs

3. Anaerobes: B. fragilis 

4. Fungi: Candida spp.

Lower Risk Community Acquired IAI Empiric Treatment…

1. Recommended: Ceftriaxone + Metronidazole, Ertapenem 

2. For Severe B-lac allergy: Ervacyclin, Moxifloxacin, Ciprofloxacin + Metronidazole

Covers: Enterobacterales, Aerobic streptococci, obligate anerobes

(Moxi is only FQ that covers anearobes) 

Higher Risk of Community Acquired IAI Empiric Treatment…

Covers pseudomonas for high risk

1. Recommended: Pip/tazo, Meropenem, Cefepime + Metronidazole

2. Severe B-lac allergy; Aztreoname + Metronidazole + Vancomycin

Healthcare-associated IAI Empiric Treatment…

1. Recommended: Pip/tazo + linezoild

   1. Impenem + vancomycin/linezolid 

   2. Meropenem + vancoymin/linezolid 

   3. Cefepime + vancomycin/linezolid 

2. Severe B-lac allergy: Aztreoname + Metronidazole + vancomycin 

Antienteroccocal Therapy…

1. Ampicillin 

2. Pip/tazo 

3. Impenem 

4. Vancomycin (E. faecium tends to be vanco-resistant)

VRE activity:

1. Linezolid 

2. Daptomycin 

3. Tigecycline

4. Eravacycline 

When is anti-MRSA TX required for healthcare associated IAI?

• Colonized with MRSA or hx of MRSA infection 

• Multiple MRSA risk factors: > 70 age, comorbidities, recent surgery, ABX use, hospitalization, nursing home, on dialysis 

First Line: vancomycin, linezolid, daptomycin

Antifungal therapy (Candida spp.) requiref for healthcare associated IAI?

→ if gram stain shows yeast

First Line: Echinocandin

Resistant Gram-negatives: ESBL EB

Resistant Gram-negatives: ESBL EB

• First Line: Impenem, Meropenem 

• Alts: Ceftazi-avibactam, Ceftolozone-tazobactam 

Resistant Gram-negatives: CRE

• First Line: Ceftazidime-avibactam, Meropenem-vaborbactam

• Alts: Impenem-relebactam, Cefiderocol

Resistant Gram-negatives: MDR-Pseudomonas

• First Line: Ceftolozane-tazobactam

• Alts: Cefiderocol, Impenem-relebactam, Ceftazidime-avibactam  

IAI Empiric Coverage Simplified: 

• uIAI peri-op = ceftriaxone + metronidazole

• cIAI low risk = ceftriaxone + metronidazole

• cIAI high risk = pip/tazo

• cIAI healthcare associated: linezolid + pip/tazo

Always cover gram positive, gram negative, and anerobes everytime