Antimicrobial activity of natural antimicrobial substances against Escherichia coli O157: H7

Due to consumer concern about the negative side effects of chemical preservatives in food, recently increasing researches have been done to find effective natural antimicrobials. The aim of this study was to investigate the antibacterial activity of eugenol in combination with acetic and lactic acids against E. coli O157: H7.

The antibacterial effects of eugenol, acetic and lactic acids were determined using minimum inhibitory concentration (MIC) methods. Fractional inhibitory concentration (FIC) and Time-Kill assays were also used to evaluate the combined antibacterial activity. 
 

Based on our results, eugenol, acetic and lactic acids inhibited the growth of E. coli O157: H7, and eugenol had the strongest effect against the bacterium. MIC values for eugenol, acetic acid and lactic acid were 0.75, 2.5 and 5 μl/ml respectively. FIC method showed that eugenol combina-tion with the organic acids had no interaction effects (1.0 >  FIC  >4.0). Time kill cureve showed that eugenol combined with lactic acid caused the death of E. coli O157: H7 in 4 h.

Eugenol, acetic and lactic acids are effective in inhibiting the growth of E. coli O157: H7  Mean while, organic acids can reduce the required amount of eugenol. Then, combination of eugenol and organic acids could provide an alternative to chemical preservatives in foods.