Antimicrobial activity of essential oils extracted from Origanum vulgare and Melaleuca armillaris against Escherichia coli isolated from poultry feces

TOSO, FEDERICO; BULDAIN, DANIEL; GORTARI CASTILLO, LIHUEL; PRIO, VERONICA; HONOR IRALA, FEDERICO; MARCHETTI, LAURA; MESTORINO, NORA

Brujas

Congreso; 15th International Congress of the European Association for Veterinary Pharmacology and Toxicology; 2023

European Association for Veterinary Pharmacology and Toxicology

Introduction: Antibiotic resistance has become a severe public threat to human health worldwide. Supplementing antibiotic growth promoters (AGPs) at subtherapeutic levels has been a commonly applied method to improve the production performance of poultry, but this practice plays a major role in the antibiotic resistance crisis and foodborne disease outbreaks. Therefore, finding alternatives to antibiotics to maintain the efficiency of broiler production and reduce the risk of foodborne disease outbreaks is a priority. Essential oils (EOs) are becoming increasingly popular as potential antibiotic alternatives for animal production based on their antibacterial properties. The aim of this study was to evaluate the in vitro susceptibility of avian E. coli strains to Melaleuca armillaris and Origanum vulgare essential oils.Materials and Methods: The EOs of M. armillaris and O. vulgare were obtained by steam distillation and their compositions were analyzed by a GC–FID–MS. Ten E. coli strains isolated from broiler rectal swabs were tested and E. coli ATCC 25922 strain was the control. The Minimum Inhibitory Concentrations (MIC) of both EOs were determined by the serial microdilution in broth in 96-wellpolystyrene microplates. The range of concentrations evaluated was 100 to 0.19 μL/mL for either EO. After that, Minimum Bactericidal Concentrations (MBC) were evaluated for the two EOs.Results: Chromatographic analysis of the M. armillaris EO revealed the presence of 1,8-cineol as the main component (72.3%), and, in lesser magnitude, limonene (7.8%) and α-pinene (6.0%). While in the O. vulgare EO the principal was carvacrol (34.91%). These chemical compounds are commonly present in EOs with high antimicrobial activity, particularly 1,8-cineol. Regarding the antimicrobial activity, the MICs were between 0.78–6.25 μL/mL and 6.25–12.5 μL/mL with MBC/MIC ratios of 2 (bactericidal) and 4 (bacteriostatic) for M. armillaris and O. vulgaris EOs, respectively.Conclusions: The antimicrobial activity of M. armillaris and O. vulgare against E. coli avian origin was confirmed in this first study. The essential oil of M. armillaris had more antimicrobial activity than O. vulgare. The beginning of antimicrobial resistance by zoonotic bacteria has important implications for public health. Therefore, the use of M. armillaris and O. vulgare essential oils alone or combined could be effective on avian E. coli strains and may be an alternative for reducing the losses caused by these bacteria in poultry production whenever a limitation in the use of traditional antibiotics.