Surgical Site Infections in Colorectal Surgery: Appropriateness of Prophylactic and Empirical Antibiotics Based on Culture Sensitivity Results in a Tertiary Hospital in Singapore

A BSTRACT Background: Surgical site infections (SSIs) are an important cause of morbidity and mortality in colorectal surgery patients. This retrospective audit assessed the predominant microbes which grow on SSIs in colorectal surgery and their respective susceptibilities to the various available antibiotics in a single institution in Singapore. Methods: A total of 111 patients were identified to have SSIs according to the definition by the Centers for Disease Control and Prevention, USA. The institution’s electronic health record was accessed to obtain the relevant information including but not limited to their wound cultures and antibiotics prescribed. This was then collated, stratified, and reorganized into an antibiogram based on the most common microbe groups. Results: The most common microbes which grew on SSIs included the Enterobacteriaceae family, Gram-positive bacteria, Pseudomonas aeruginosa , and anaerobes. There was no significant variation in the growth of these microbial groups across type of surgery, surgical approach, urgency of surgery, and type of SSI. The antibiogram showed an overall low susceptibility (<20%) to Augmentin throughout the various types of SSIs, while there was a consistently high susceptibility (>75%) throughout the various types of SSIs to aminoglycosides, quinolones, and macrolides tested. 82.6% of patients were on Augmentin prophylaxis. Conclusion: There is a low rate of susceptibility to Augmentin in the microbes growing on SSIs. Antimicrobial susceptibilities suggest an alternative empirical regimen such as gentamicin and metronidazole or ciprofloxacin and metronidazole. Further prospective studies should be performed to confirm their efficacy.