| Congresso Brasileiro de Microbiologia 2023 | Resumo: 1190-1 | ||||
Resumo:Listeria monocytogenes is a bacterial foodborne pathogen causative of a severe disease in humans, especially harmful for the elderly, pregnant women, and newborns. One strategy for its control is the use of nisin in different types of foods. The combination of nisin and curcumin is not well understood and could be a novel strategy for control. The aim of this study was to evaluate the response of prfA and sigB genes, which are related to stress response and pathogenicity, of L. monocytogenes serotype 1/2a against nisin and curcumin in combination. For the analysis, nisin was used in neutral pH (7.0) (NN) and at pH 6.0 (N6), non-heated curcumin (NHC), and heated curcumin (60°C/30 min) (HC), along with a wild-type of L. monocytogenes 1/2a strain and its isogenic mutant (ΔprfA ΔsigB). The minimum inhibitory concentration (MIC) was determined using the microdilution method in a 96-well plate. The MIC values obtained previously were used to establish the maximum concentration for the checkerboard assay. The synergistic interaction was calculated using the fractional inhibitory concentration index (FICI), considering synergy when FICI ≤ 0.5. Statistical analyses were performed using the nonparametric Wilcoxon test with a significance level of 0.05. The MIC results of curcumin alone demonstrated that the wild strain was more resistant (p < 0.05) to NHC when compared to its mutant, indicating a defense response of prfA and sigB genes against the antimicrobial activity of curcumin. The opposite was observed for HC, with the wild strain being more sensitive when compared to its mutant. N6 was more efficient against both strains (wild and mutant) when compared to NN, and there was no statistical difference between the wild-type and mutant strains (p > 0.05). Combinations of NN+NHC, N6+NHC, and N6+HC were equally synergistic. The NN+CA combination was also synergistic but less efficient when compared to the other three combinations. When the wild-type and its mutant were compared, the statistical results indicated a difference (p < 0.05) in the response to combinations tested. NN+NHC was more efficient against the mutant strain, and N6+NHC was more efficient against the wild-type strain. This could be explained by the acidic pH, which promotes better nisin activity and stability of curcumin. The antimicrobial combination of nisin and curcumin was not affected by the prfA and sigB genes' response when curcumin is not heated and is combined with nisin at pH 6.0. Under these conditions, the combination of nisin and curcumin presents potential usage for the control of L. monocytogenes in foods. Palavras-chave: Listeria monocytogenes, antimicrobial, food, nisin, curcumin Agência de fomento:CNPq e FAPESP | |||||