310 Using synergistic antibacterial combinations based on vegetable essential oils to replace feeding antibiotics

Abstract

Abstract Vegetable essential oils, medium-chain fatty acids and organic acids have great potential in the development of alternatives to feeding antibiotics, but many problems in practice limit their application, such as irritating odor, poor water solubility, easy oxidation and volatility. In this study, we found that vegetable essential oils (carcilol, cinnamaldehyde, terptol-4) and medium chain fatty acids (octanoic acid and nonanoic acid) or organic acids (citric acid) had significantly synergistic bactericidal effects on enterotoxigenic Escherichia coli and Salmonella enteribacilli, which are both common pathogens causing piglets diarrhea. Furthermore, we also compared the tolerances of the enterotoxigenic Escherichia coli against plant essential oils (cinnamaldehyde, carcocol, 4- terptol), medium chain fatty acids (octanoic acid and nonylic acid), organic acids (citric acid), and commonly used antibiotic growth promoter (gentamycin sulfate). They were in vitro cultured with ETEC strain for 30 consecutive generations and the minimum inhibitory concentration (MIC) value was detected. The results showed that the MIC values of carvonol, cinnamaldehyde, terpineol-4, octanoic acid, nonylic acid, and citric acid against the ETEC bacteria increased by 5, 3, 1, 0.3, 0.4 and 0 times. But the MIC value of gentamicin against ETEC bacteria increased, in the 20th generation, by more than 64 times. In conclusions, the synergistic bactericidal combination based on the plant essential oil and middle chain fatty acid or organic acid may be a better strategy to replace feeding antibiotics because their synergistic bactericidal combination can greatly reduce the effective concentration of plant essential oil, medium chain fatty acid and organic acid, thus alleviating to a certain extent the shortcomings of unstable effects caused by the irritating odor, the poor water solubility, easy oxidation and volatility. The synergistic bactericidal combination based on plant essential oils are also relatively difficult to cause bacterial tolerance and alleviate bacterial resistance to a certain extent.