Inhibitory activity of natural antimicrobial compounds alone or in combination with nisin against Enterobacter sakazakii

Abstract

Aim: To determine the antimicrobial activity of natural organic compounds alone and in combination with nisin on the growth of Enterobacter sakazakii in laboratory media. Methods and Results: The minimum inhibitory concentrations (MIC) of five natural organic compounds were determined, and their effects in combination with nisin were evaluated by comparing treatment with each natural organic compound alone and in combination with 25 mg ml(-1) nisin in tryptic soy broth. Among the tested natural organic compounds, the MIC of carvacrol and thymol was 1.25 mmol l(-1) and showed the strongest inhibitory activity against E. sakazakii, whereas the MIC of cinnamic acid was higher than 5 mmol l(-1), and therefore showed the weakest inhibitory activity. However, the combination of each compound with nisin did not result in the enhancement of their antimicrobial activities except when nisin was combined with diacetyl. Conclusions: The order of inhibition attributed to natural organic compounds was carvacrol = thymol > eugenol > diacetyl > cinnamic acid, and only the combination of diacetyl and nisin showed a synergistic effect of inhibiting the growth of E. sakazakii. Significance and Impact of the Study: This study shows the potential of natural organic compounds for controlling E. sakazakii.