Uselessness of microbiological samples in acute appendicitis with frank pus: to collect or not to collect?

Current use of antimicrobial therapy is prophylactic, empirical and broad spectrum. But, the age-old practice of obtaining cultures still remain. The aim of this study was to evaluate bacterial etiology and adequacy of antibiotic prophylaxis in patients diagnosed with acute appendicitis to help determine the utility of intraoperative cultures in guiding clinical decision-making.

A retrospective analysis of a prospectively constructed database of all patients who underwent appendectomy from September 2013 to November 2016 was performed.

456 patients underwent surgery for acute appendicitis in our academic hospital. 101 patients (22.1%) had intraoperative swabs taken, and the cultures were positive in 57.4% of patients. These 101 patients comprise our study group. The most commonly recovered species were E. coli, Streptococcus spp., Bacteroides fragilis, Enterococcus faecium, Pseudomonas aeruginosa, Klebsiella pneumoniae, and Proteus. In the comparison between positive and negative swab, there were no differences in terms of surgical site infection, deep infection, and in terms of Clavien-Dindo classification. An appropriate empiric therapy was set in 88.5% and inappropriate in 11.5%. No differences in terms of surgical site infection or in length of stay (p = 0.657) were found, with a median of 7 days in both groups.

The etiological agents causing peritonitis due to acute appendicitis are predictable and empiric-targeted antibiotic therapy is effective in a high percentage of patients. The postoperative patient outcome may be dependent on the severity of the appendicitis more than on the results of the swab at the time of surgery. In this study, intraoperative culture was not associated with the choice of antibiotics, incidence of SSI, DPI or the length of stay.