Appendicitis Organism-Specific Therapy 

Organism-specific therapeutic regimens for appendicitis in adults are outlined below, including those for anaerobic organisms (including Bacteroides fragilis, Clostridium spp, and Prevotella spp), aerobic gram-negative bacilli (including Escherichia coli, Klebsiella spp, and Proteus mirabilis), Pseudomonas aeruginosa, streptococci, enterococci, and mixtures of aerobes and anaerobes. ^{[1, 2, 3, 4]}

See Appendicitis: Avoiding Pitfalls in Diagnosis, a Critical Images slideshow, to help make an accurate diagnosis.

Anaerobic organisms (including Bacteroides fragilis, Clostridium spp, Prevotella spp)

See the list below:

• Clindamycin 600 mg IV q8h or

• Metronidazole 500 mg IV q8h or

• Ertapenem 1 g IV daily or

• Ampicillin-sulbactam 3 g IV q6h or

• Ticarcillin-clavulanate 3.1 g IV q4-6h or

• Ceftolozane/tazobactam 1.5 g IV q8h plus metronidazole 500 mg IV q8h

Aerobic gram-negative bacilli (including Escherichia coli, Klebsiella spp, Proteus mirabilis)

See the list below:

• Aztreonam 1-2 g IV q8h or

• Ampicillin 2 g IV q4h for or

• Ciprofloxacin 400 mg IV q12h or

• Ertapenem 1 g IV daily or

• Levofloxacin 750 mg IV q24h or

• Gentamicin 5-7 mg/kg IV q24h or

• Cefoxitin 2g IV q8h or

• Cefotetan 2 g IV q12h or

• Cefotaxime 1-2 g IV q6-8h or

• Ceftriaxone 1-2g IV q24h or

• Ceftolozane/tazobactam 1.5 g IV q8h plus metronidazole 500 mg IV q8h

Pseudomonas aeruginosa

See the list below:

• Aztreonam 1-2 g IV q8h or

• Ciprofloxacin 400 mg IV q12h or

• Piperacillin-tazobactam 4.5 g IV q6h or

• Doripenem 500 mg IV q8h or

• Imipenem-cilastatin 500 mg IV q6h or

• Meropenem 1 g IV q8h or

• Ceftolozane/tazobactam 1.5 g IV q8h plus metronidazole 500 mg IV q8h

Streptococci and enterococci

See the list below:

• Ampicillin-sulbactam 3 g IV q6h or

• Ticarcillin-clavulanate 3.1 g IV q4-6h or

• Piperacillin-tazobactam 3.375-4.5 g IV q6-8h or

• Doripenem 500 mg IV q8h or

• Imipenem-cilastatin 500 mg IV q6h or

• Meropenem 1 g IV q8h or

• Ceftolozane/tazobactam 1.5 g IV q8h plus metronidazole 500 mg IV q8h

Mixture of aerobes and anaerobes

See the list below:

• Cefoxitin 2g IV q8h or

• Cefotetan 2 g IV q12h or

• Ticarcillin-clavulanate 3.1 g IV q4-6h or

• Piperacillin-tazobactam 3.375-4.5 g IV q6-8h or

• Ampicillin-sulbactam 3 g IV q6h or

• Doripenem 500 mg IV q8h or

• Imipenem-cilastatin 500 mg IV q6h or

• Meropenem 1 g IV q8h or

• Ertapenem 1 g IV daily or

• Moxifloxacin 400 mg IV q24h