Implications of bacteriological study in complicated and uncomplicated acute appendicitis

Bacteriological sample in the presence of intraabdominal free fluid is necessary to adapt the antibiotherapy and to prevent the development of resistance. The aim was to evaluate the differences between uncomplicated (UAA) and complicated acute appendicitis (CAA) in terms of bacterial culture results and antibiotic resistance, and to evaluate the factors linked with CAA.

We performed a single-center, retrospective observational study of all consecutive patients who presented with appendicular peritonitis and underwent emergent surgery in a tertiary referral hospital in Brussels, Belgium, between January 2013 and December 2020. The medical history, parameters at admission, bacterial culture, antibiotic resistance, and postoperative outcomes of 268 patients were analyzed. UAA was considered catarrhal or phlegmonous inflammation of the appendix. CAA was considered gangrenous or perforated appendicitis.

Positive microbiological cultures were significantly higher in the CAA group (68.2% vs. 53.4%). The most frequently isolated bacteria in UAA and CAA cultures were Escherichia coli (37.9% and 48.6%). Most observed resistances were against ampicillin (28.9% and 21.7%) and amoxicillin/clavulanic acid (16.4% and 10.5%) in UAA and CAA, respectively. A higher Charlson comorbidity index, an elevated white blood cell count, an open procedure, and the need for drainage were linked to CAA. Culture results, group of bacterial isolation, and most common isolated bacteria were not related to CAA.

CAA presented a higher rate of positive cultures with increased identification of gram-negative bacteria. Bacterial culture from the peritoneal liquid does not reveal relevant differences in terms of antibiotic resistance.