Background: Complex post-operative infections, defined as cIAI lacking a straightforward surgical alternative, are commonly managed with percutaneous drainage. Absent physical tissue manipulation and debridement, it is not known whether standard rules of antimicrobial therapy, in particular, early presence of antimicrobial therapy covering all pathogens subsequently identified on culture, pertains. We therefore chose to review patients with these complex intra- abdominal infections treated at our institution to explore the effect of adequate empiric antibiotic therapy on outcomes.

Methods: A retrospective review of patients with intra-abdominal infection and severe complicating illnesses treated from January 2007 through February 2008 was conducted. Treatment failure was defined as conversion to open debridement, persistent positive infection greater than 5 days from initial procedure, or death from overwhelming sepsis.

Results: 94 patients met inclusion criteria. Demographics showed a male to female ratio of 1.5:1 with an average age of 50 years. Infections occurring after bowel resection (16), pancreatic resection (12), liver resection (11), acute pancreatitis (11) and bowel perforations (7) accounted for over 60% of all cases.

Gram positives were most commonly isolated from initial drainage procedures (56%), followed by gram negatives (41%) and Candida (3%). Antibiotic therapy for gram-negative organisms was active against all encountered. However, in 2 of 5 patients with Methicillin-resistant Staphylococcus aureus (MRSA) initial therapy did not include vancomycin. For 8 patients with Vancomycin-resistant Enterococcus (VRE), none were initially treated.

Twenty five patients required repeated drainage more than 5 days after the initial procedure. VRE and MRSA were the most commonly isolated organisms in patients requiring repeat drainage procedures (53%). Six patients (6.4%) died despite maximal medical management.

Conclusion: Appropriate percutaneous drainage of fluid collections is a viable method of source control in patients with complex post-operative intra-abdominal infections. Our data support the notion that antimicrobial therapy remains an important adjunct for optimal medical management in these patients. VRE and MRSA are major pathogens associated with treatment failure.