Combating Campylobacter Resistance in Moroccan Poultry Using Essential Oil-Ciprofloxacin Combination

Campylobacter is one of the leading causes of gastroenteritis, and the increasing prevalence of antimicrobial resistance calls for new treatment alternatives, such as essential oils (EOs).

This study aims to investigate the prevalence of antimicrobial-resistant Campylobacter strains recovered from poultry in Morocco, and to evaluate the antibacterial effects of the commercial EOs from cinnamon (CIEO), clove (CLEO) and oregano (OREO) alone and in combination with ciprofloxacin on Campylobacter coli and Campylobacter jejuni using in vitro and in silico approaches.

A total of 643 caecal samples were collected from poultry across four regions of Morocco, and C. coli and C. jejuni strains were isolated and tested for antibiotic susceptibility, following EUCAST guidelines. The antibacterial activity of selected EOs was assessed individually and in combination with antibiotics through broth microdilution and checkerboard assays. Additionally, molecular docking was conducted between the major EOs chemotypes and resistance-associated protein targets (RNApα, CmeB, CmeR, DHPS, Erm(B), GyrA, GyrB, PBP2 and TetR).

The prevalence of Campylobacter spp. among the collected samples was 15.52% (100/643). Many isolates exhibited strong resistance to nalidixic acid (90%), ciprofloxacin (85%) and tetracycline (78%). The studied EOs demonstrated a high antibacterial activity, with the MIC value ranging from 0.0312% to 0.0625% (v/v). A high level of synergism was achieved with OREO, while the interactions with CIEO and CLEO were considered antagonistic. In silico molecular docking revealed that caryophyllene exhibited strong binding affinities towards key resistance-associated proteins, including GyrB (binding energy: -7.4 kcal/mol), CmeB (-7.5 kcal/mol) and PBP2 (-6.4 kcal/mol), suggesting potential interference with DNA gyrase activity, multidrug efflux and cell wall synthesis, respectively.

These findings suggest that selected EOs, particularly OREO, warrant further investigation as potential adjuncts to conventional antibiotics against multidrug-resistant Campylobacter.