Post-Appendectomy Wound Infections

Causative Organisms

The most common organisms in post-appendectomy wound infections are polymicrobial, dominated by Escherichia coli (85% of cases), followed by Klebsiella pneumoniae (26%), Streptococcus species (25%), Enterococcus species (18%), and anaerobes, particularly Bacteroides fragilis 1, 2, 3, 4
Streptococcus species (including viridans group streptococci) are present in 25% of infections 1, 4
Enterococcus species are isolated in 18% of cases and are associated with worse outcomes in intra-abdominal infections 1, 4
Bacteroides fragilis is the dominant anaerobic pathogen, found in 78% of appendiceal infections and over 90% of wound infections following appendectomy 2, 3
Anaerobes are present in approximately 30% of post-operative peritonitis cases 4

This patient presenting weeks post-operatively represents a healthcare-associated infection (HA-IAI), which has different microbiology than community-acquired infections 1, 4
Post-operative infections show lower susceptibility rates and different resistance patterns compared to community-acquired cases 4
Enterococci are isolated in 47.1% of post-operative peritonitis cases, compared to lower rates in community-acquired infections 4
Candida species appear in 28.9% of post-operative cases 4

Extended-spectrum beta-lactamase (ESBL)-producing Enterobacteriaceae are increasingly common, particularly with recent antibiotic exposure (within 90 days) 1, 4
The proportion of multidrug-resistant organisms (MDRO) increases with time from initial surgery 4

For post-appendectomy wound infections with fever, empiric antibiotics must cover both aerobic gram-negative rods (especially E. coli) and anaerobes (especially Bacteroides fragilis) 1, 2, 3
The Infectious Diseases Society of America recommends cephalosporin + metronidazole (e.g., cefazolin or cefoxitin plus metronidazole) as a first-line regimen 5, 7
The Society of Critical Care Medicine suggests fluoroquinolone + metronidazole (e.g., levofloxacin plus metronidazole) as an alternative first-line regimen 5, 6
The American College of Surgeons recommends carbapenem monotherapy (e.g., ertapenem, meropenem) for patients with severe infections or those who are at high risk for resistance 5, 6

Collect 1-2 mL of fluid or tissue in an anaerobic transport system 1, 2
Inoculate directly into aerobic and anaerobic blood culture bottles when possible 2, 3
Obtain Gram stain and culture of any purulent drainage before starting antibiotics 5, 7

Reassess the wound daily for improvement 7
Monitor temperature curve and vital signs 7
Adjust antibiotics based on culture results when available 1, 4
Consider imaging (CT) to evaluate for deeper abscess if no improvement within 48-72 hours 7