Background: Acute appendicitis (AA) is the most frequent surgical emergency in the paediatric population. Complicated appendicitis (CA) makes up to 30% of cases and is inextricably linked to postoperative infectious complications (POIC). A recent study carried out at our institution showed that Amoxicillin-Clavulanic acid resistant Escherichia coli (E.coli) in CA is significantly linked to POIC. These findings led to a pivotal change in the empirical antibiotic protocol (Amoxicillin-Clavulanic acid changed to Ceftriaxone/Metronidazole) with the aim of reducing POIC in CA in our local population. The primary aim of this study was to analyse the microbiology and resistance profiles of pathogens of CA in our institution since the implementation of the new antibiotic protocol and its effect on the POIC rate.
Methods: We designed a retrospective comparative cohort study. During the defined study period (01.01.17 to 31.07.20), electronic medical records were analysed for cases of AA, retaining only those patients who had an intraoperative diagnosis of CA and had a peritoneal swab taken. Postoperative outcomes, microbiology and antibiotic resistance of peritoneal swabs were analysed in all cases.
Results: During the study period, a total of 553 patients under the age of 18 underwent an appendectomy. Of these, 95 (17%) presented as CA and a further 11 (12%) developed POIC. The most frequent pathogens found in CA were E. coli (66%), Streptococcus anginosus (45%), and Bacteroides fragilis (22%). Pseudomonas aeruginosa was present in 17% of CA. The most common pathogens involved in POIC mirrored exactly the distribution found in CA without POIC. Antibiotic susceptibility analysis showed that 12 (18%) species of E. coli were resistant to Amoxicillin-clavulanate but sensitive to Ceftriaxone/Metronidazole, with only one causing a POIC. Compared to our previous study, there was a small decrease in POIC from 16% to 12%, as well as an increase in Amoxicillin-Clavulanic acid resistant E.coli from 14% to 18%. The number of POIC caused by Amoxicillin-Clavulanic acid resistant E. coli drastically decreased from 28% to 9%.
Conclusions: This retrospective comparative study pooling data from a period of over 10 years demonstrated a decrease in the rate of POIC due to Amoxicillin-Clavulanic acid resistant E. coli in CA.
These findings accentuate with the utmost importance the need to implement evidence-based treatment protocols based on local microbiology profiles and resistance rates in order to optimize postoperative antibiotics in CA.