Activity of natural antimicrobial compounds against Escherichia coli and Salmonella enterica serovar Typhimurium.
OBJECTIVE
The objective of this study was to evaluate the inhibitory activity of several natural organic compounds alone or in combination with nisin against Escherichia coli and Salmonella Typhimurium.


RESULTS
The minimum inhibitory concentration (MIC) of five natural organic compounds were determined, and the effect of their combinations with nisin was evaluated by the checkerboard assay using the Bioscreen C. As expected, nisin by itself showed no inhibition against either of the Gram-negative bacteria. Thymol was found to be the most effective with the lowest MIC values of 1.0 and 1.2 mmol 1-1 against Salm. Typhimurium and E. coli, respectively. After thymol, the antimicrobial order of the natural organic compounds was carvacrol > eugenol > cinnamic acid > diacetyl. However, the combination of nisin with the natural organic compounds did not result in the enhancement of their antimicrobial activities. On the contrary, combination of nisin with diacetyl against Salm. Typhimurium resulted in an antagonism of diacetyl activity.


CONCLUSIONS
While the individual natural organic compounds showed inhibitory activity against the two Gram-negatives, their combinations with nisin showed no improvement of antimicrobial activity.


CONCLUSIONS
This study shows the potential of the natural organic compounds to control E. coli and Salm. Typhimurium.
Olasupo
N A
NA
Department of Microbiology, Lagos State University, Ojo, Lagos, Nigeria.
Fitzgerald
D J
DJ
Gasson
M J
MJ
Narbad
A
A
D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D002934:Cinnamates / Q000494:pharmacology; D000081007:Cymenes; D003931:Diacetyl / Q000037:antagonists & inhibitors / Q000494:pharmacology; D004359:Drug Therapy, Combination / Q000494:pharmacology; D004926:Escherichia coli / Q000187:drug effects* / Q000254:growth & development; D005054:Eugenol / Q000494:pharmacology; D066298:In Vitro Techniques; D008826:Microbial Sensitivity Tests; D039821:Monoterpenes / Q000494:pharmacology; D009561:Nisin / Q000494:pharmacology; D012486:Salmonella typhimurium / Q000187:drug effects* / Q000254:growth & development; D013943:Thymol / Q000494:pharmacology
D000900:Anti-Bacterial Agents; D002934:Cinnamates; D000081007:Cymenes; D039821:Monoterpenes; C029010:cinnamic acid; D009561:Nisin; D013943:Thymol; D005054:Eugenol; C073316:carvacrol; D003931:Diacetyl