10109

SYNERGIC INTERACTION BETWEEN SUBSTANCES PRESENT IN ESSENTIAL OILS OF PLANTS AND BACTERIOCINS AGAINST S. Typhimurium, S. aureus and E. coli.

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Essential oils and extracts of aromatic plants has been shown efficient in inhibiting the growth of pathogens and food spoilage, thus increasing interest in using them as natural preservatives. In this work we evaluated the synergistic action of cinnamaldehyde, carvacrol, eugenol, substances with antimicrobial activity, present in essential oils of spices and a bacteriocin (nisin) against isolates of S. Typhimurium ATCC 14028, S. aureus ATCC 25923 and E. coli ATCC 25922. We used the checkerboard method to obtain the fractional inhibitory concentration (FIC), where the substance A was diluted along in the X axis, and the substance B, in Y axis. Bacterial suspension (5.105 CFU/mL) was inoculated into the microplate and incubated at 35ºC for 24h.The indices were calculated as FIC.A + FIC.B where FIC.A and FIC.B are the minimum concentrations that inhibit the growth of bacteria for substances A and B, respectively. The results were interpreted as synergism (FIC <0.5), addition (0.5 ≤ FIC ≤ 1), indifference (1 ≤ <FIC 4) or antagonism (FIC> 4). S. aureus ATCC 25923 showed indifference for all combinations performed (nisin + cinnamaldehyde; eugenol + nisin; carvacrol + nisin; cinnamaldehyde + carvacrol; cinnamaldehyde + eugenol and eugenol + carvacrol). The results for S. Typhimurium ATCC 14028 and E. coli ATCC 25922 were similar, showing synergism for the combination eugenol + carvacrol and indifference to others combinations. These results demonstrate that interactions between these substances were not satisfactory with the exception of carvacrol + eugenol interaction which was efficient for Gram-negative bacteria.