Bacterial culture and antibiotic susceptibility in patients with acute appendicitis

Essential treatment of acute appendicitis is surgical resection with the use of appropriate antibiotics. In order to effectively treat acute appendicitis, it is important to identify the microorganism of acute appendicitis and evaluate the effective antibiotics.

A total of 694 patients who underwent appendectomy for acute appendicitis and had positive microbial result between 2006 and 2015 were recruited. For microbial assessment, luminal contents of the appendix were swabbed after appendectomy. In patients with periappendiceal abscess, the specimens were obtained from abscess fluid. The patient characteristics, operative data, use of antibiotics, the results of microbiology, and postoperative morbidities including surgical site infection (SSI) were retrospectively reviewed.

The mean age was 38.2 (± 19.8) years, and 422 patients (60.8%) were male. Most of the operations were performed by conventional laparoscopy (83.1%), followed by single-port laparoscopy (11.8%). The most common microorganism was Escherichia coli (64.6%), which was susceptible to amoxicillin/clavulanate, ciprofloxacin, most cephalosporins, piperacillin/tazobactam, and imipenem. The second most common microorganism was Pseudomonas aeruginosa (16.4%), which was resistant to amoxicillin/clavulanate and cefotaxime. The rate of postoperative morbidity was 8.6%, and the most common type was superficial SSI (6.2%), followed by ileus (1.2%), gastroenteritis (0.7%), and organ/space SSI (0.3%). P. aeruginosa (odds ratio = 2.128, 95% confidence interval 1.077-4.206, P = 0.030) was the only significant microorganism associated with SSI according to multivariate analysis adjusting for other clinical factors.

In perforated appendicitis, the use of empirical antibiotics seems to be safe. In some cases of Pseudomonas infection, adequate antibiotics should be considered.