Culture-based Bacterial Evaluation of the Appendix Lumen and Antibiotic Susceptibility of Acute Appendicitis in Japan: A Single-center Retrospective Analysis

The question of whether to perform an appendectomy or conservative treatment for acute appendicitis can differ depending on the facility or surgeon, but antibiotic treatment is administered regardless of whether an appendectomy or conservative treatment is selected. We investigated the contemporary bacteriology for acute appendicitis and evaluated the antibiotic sensitivity of the bacteria that are currently associated with appendicitis. We retrospectively analyzed the bacterial culture results and antibiotic susceptibility of 141 patients who underwent appendicitis surgery, including the identification and antimicrobial susceptibility of the cultured bacteria within the excised appendices. Bacterial cultures were positive in 131 cases (92.9%). The most commonly isolated bacteria were Escherichia coli (90 isolates, 66.7%), followed by Enterococcus species (n = 19, 14.5%), Pseudomonas aeruginosa (n = 18, 13.7%), Streptococcus species (n = 15, 11.5%), and Klebsiella species (n = 8, 6.1%). Eight strains (8.8%) of E coli were extended-spectrum β-lactamase producers, and ten strains (11.1%) were fluoroquinolone-resistant. Tazobactam/piperacillin and meropenem inhibited the growth of 100% of the major identified bacteria. The patients with appendicoliths had a significantly higher bacterial culture rate. Enterococcus species were frequently isolated from the patients with complicated appendicitis. For the antibiotic treatment of appendicitis, it is essential to understand the patient's microbiological profile and antibiotic susceptibilities. Research from Asian countries such as Japan can enhance our knowledge of regional antibiotic resistance patterns and inform effective treatment strategies.