Antimicrobial effects of citrus oil on concurrent bacterial and fungal isolates from broiler chicken

Extensive antibiotic use in poultry has accelerated the emergence of multi-drug-resistant pathogens. This study investigated the prevalence of Escherichia coli, Pseudomonas aeruginosa, Candida albicans and Aspergillus spp. in broiler chickens and evaluated the in vitro efficacy of citrus oil as a natural antimicrobial agent. Bacteriological and mycological examination of 63 samples from diseased broilers revealed a high   prevalence of infection. The most common isolates were P. aeruginosa (23.8%, 15/63) and E. coli (19%, 12/63). Co-infections with both bacteria and fungi were also frequent, found in 19% (12/63) of samples. Antimicrobial testing revealed widespread resistance. E. coli isolates were 100% resistant to cephalosporins and showed high resistance (83.3%) to aminoglycosides, tetracyclines, and fluoroquinolones. P. aeruginosa isolates were 100% resistant to nearly all tested antibiotics, demonstrating a severe multi-drug-resistant phenotype.
Assessing the effect of 1% citrus oil on these resistant isolates, revealed inhibition of the growth of 50% of E. coli and 20% of P. aeruginosa isolates. Moreover, it had a powerful synergistic effect on grown isolates, re-sensitizing of two E. coli isolates that changed to susceptible to oxytetracycline, apramycin, and aztreonam. Whereas P. aeruginosa, four isolates changed to susceptible to tobramycin, ofloxacin, ceftazidime, and apramycin and two isolates changed to susceptible to streptomycin, cefotaxime sodium,doxycyclineHCl,chloramphenicol,sulfamethoxazole-trimethoprim, oxytetracycline, and cefuroxime sodium. Fungal isolates showed weak growth with 1% citrus oil and were completely inhibited at a 1.5% concentration.
In conclusion, citrus essential oil shows great promise as a therapeutic agent because it has antibacterial, antifungal effects and can re-sensitize highly resistant bacteria, such as P. aeruginosa and E. coli, conventional antibiotics These findings suggest a crucial new strategy for managing the global threat of antimicrobial resistance.