Antimicrobial Efficacy of Cinnamon Essential Oil against Avian Pathogenic <i>Escherichia coli</i> from Poultry

Colibacillosis, caused by <i>E. coli</i>, is responsible for economic losses in the poultry industry due to mortality, decreased production, and the cost of antibiotic treatments. Prevention of colibacillosis is based on improved biosecurity measures and the use of the vaccine performed with O78 <i>E. coli</i> strains, which is responsible for most cases of colibacillosis. Recently, there has been increased interest in other infection control methods, such as the use of natural compounds. The aim of this study was to evaluate the antimicrobial efficacy of cinnamon essential oil (CEO) against <i>E. coli</i> strains isolated from poultry. The MIC₅₀ and MIC₉₀ of CEO were determined by testing 117 strains belonging to serogroups O78, O2, O128, O139, isolated from laying hens (91 strains), broilers (10 strains), and turkeys (16 strains). The bacterial strains were tested at cell densities of 10⁸ and 10⁶ CFU/mL. At the cell density of 10⁸ CFU/mL, MIC₅₀ and MIC₉₀ were 0.4 and 0.5 µL/mL for most of the tested strains, while they corresponded to 0.5 µL/mL for all strains isolated from broilers and for strains belonging to serogroup O139. At the cell density of 10⁶ CFU/mL, MIC₅₀ and MIC₉₀ were 0.3 and 0.4 µL/mL, regardless of bird species of origin and for strains belonging to serogroups O78 and O2. In addition, a concentration of 0.04 µL/mL of CEO corresponded both to MIC₅₀ and MIC₉₀ for strains belonging to serogroups O139 and O128. Based on these results, cinnamon essential oil showed an effective antibacterial activity against <i>E. coli</i> strains from poultry and could find field application for the prevention of colibacillosis.