ANTIBACTERIAL ACTIVITY OF EO-FIT® SWINE AGAINST SEVERAL COMMON ENTEROPATHOGENS IN SWINE PRODUCTION

Essential oils (EOs) have different mechanisms, most of them targeting the bacterial wall. This fact can explain differences in the effectivity of EOs between Gram-positive and Gram-negative bacteria. Therefore, combining certain EOs can broaden their individual spectrum of efficacy due to potential synergistic effects. This trial aimed to test the in vitro antibacterial activity of EO-FIT® Swine against a collection of relevant bacterial pathogens in swine production. The Gram-negative bacterial species chosen were Salmonella enterica ssp. enterica, Escherichia coli and Brachyspira hyodysenteriae and the Gram-positive were Clostridium perfringens and Streptococcus suis. In addition, Lactobacillus fermentum was included to compare the susceptibility of this beneficial intestinal bacteria with the enteropathogens’. The broth microdilution method at pH 6 and the subculturing from wells without bacterial growth were used to determine the minimum concentration necessary to inhibit (MIC) or kill (MBC) the 50% and 90% (MIC_50/90/MBC_50/90) of the population of every bacteria. The results showed that the lowest MIC_50/90 and MBC_50/90 were observed when EO-FIT® Swine was tested against B. hyodysenteriae, while there were no differences in the results obtained against the other bacterial pathogens. In contrast, the highest bacteriostatic/bactericidal concentrations were obtained against L. fermentum. These results suggest that EO-FIT® Swine is equally effective against the tested bacterial pathogens regardless of their category, Gram-positive or Gram-negative. It could also be concluded that B. hyodysenteriae was the most susceptible enteropathogen to EO-FIT® Swine. However, the in vivo effect of EO-FIT® Swine must be further studied to fully understand its mechanism of action.