Appendicitis Organism-Specific Therapy 

Updated: Dec 29, 2021
  • Author: Mityanand Ramnarine, MD, FACEP; Chief Editor: Thomas E Herchline, MD  more...
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Organism-Specific Therapeutic Regimens

Treatment regimens are included below for the most common isolates associated with acute appendicitis. Guideline-directed therapy focuses on the empiric treatment of these organisms, which includes Escherichia coli and other coliforms, anaerobes, and gram-positive cocci. Thus, organism-specific therapeutic regimens for appendicitis include coverage for anaerobic organisms (including Bacteroides fragilis, Clostridium spp, and Prevotella spp), aerobic gram-negative bacilli (including E coli, Klebsiella spp, and Proteus mirabilis), Pseudomonas aeruginosa, streptococci, enterococci, and mixtures of aerobes and anaerobes. [1, 2, 3, 4]

A single-drug, broad-spectrum antibiotic such as piperacillin-tazobactam or multidrug regimens may be initially necessary to achieve wide-spectrum coverage of multiple organisms. Later, therapy can be further narrowed on the basis of sensitivities if microbiology culture data become available to the healthcare provider. [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, Peptostreptococcus spp)

Lincomycins

Nitroimidazoles

Carbapenems

Penicillin/beta lactamase

Combination cephalosporin/beta lactamase/nitroimidazole

Facultative aerobic gram-negative bacilli (including E coli, Klebsiella spp, P mirabilis)

Carbapenems

Penicillins

Fluoroquinolones

Cephalosporins

Combination cephalosporin/beta lactamase/nitroimidazole

Lincomycins

Pseudomonas aeruginosa

Carbapenems

Fluoroquinolones

Beta lactamase

Carbapenem/dehydropeptidase inhibitor

Combination cephalosporin/beta lactamase/nitroimidazole

Streptococci and enterococci

Penicillin/beta lactamase

Beta lactamase

Carbapenems

Carbapenem/dehydropeptidase inhibitor

Combination cephalosporin/beta lactamase/nitroimidazole

Mixed flora: aerobes and anaerobes

Cephalosporins

Beta lactamase

Penicillin/beta lactamase

Fluoroquinolones

Carbapenems

Carbapenem/dehydropeptidase inhibitor