Efeito do óleo essencial de Origanum vulgare L. (Orégano) sobre o desenvolvimento de tolerância direta e cruzada em cepas de Staphylococcus aureus isoladas de alimentos

• Autor(a) principal: Tavares, Adassa Gama
• Data de Publicação: 2014
• Tipo de documento: Dissertação
• Idioma: por
• Título da fonte: Biblioteca Digital de Teses e Dissertações da UFPB
• Texto Completo: https://repositorio.ufpb.br/jspui/handle/tede/4300
• topic: Óleo essencial; Staphylococcus; Tolerância; Conservação de alimentos; Essential oil; Staphylococcus; Tolerance; Food preservation; CNPQ::CIENCIAS DA SAUDE::NUTRICAO

The development of tolerance in S. aureus when exposed to sublethal stress conditions used in food preservation has been observed. Despite the use of the essential oil from Origanum vulgare L. (OVEO) as a preservative in food be considered a promising alternative, there is a lack of scientific studies about its ability to induce the development of direct tolerance and cross-tolerance by food-borne pathogen bacteria. The aim of this study was to investigate the capability of the OVEO to inhibit the growth of Staphylococcus aureus strains isolated from foods, and to evaluate the development of direct tolerance and/or cross-tolerance to salts and organic acids typically used by the food industry after habituation in sublethal amounts of OVEO. Four strains of S. aureus (FRI-S-6; FRI-196-3; FRI-326; ATCC 13565) producing enterotoxins A, B, D and E were used as test-organisms. The values of Minimum Inhibitory Concentration (MIC) of OVEO, sodium chloride (NaCl), potassium chloride (KCl), acetic acid (AA) and lactic acid (LA) were determined by the microdilution method. The ability of strains of enterotoxigenic S.aureus to develop direct tolerance and/or cross-tolerance to NaCl, KCl, AA and LA was evaluated after the exposure of these strains to sulethal amounts (½ MIC and ¼ MIC) of OVEO in Brain Heart Infusion broth (BHI) for 72 hours, followed by the determination of the MIC values of the tested antimicrobial agents. The induction of direct tolerance and/or cross-tolerance was assessed by comparing the MIC values of the antimicrobials against the tested strains before and after the habituation treatment with sublethal amounts of OVEO. The assays were performed in triplicate and the results were expressed in modal value. MIC values of OVEO, NaCl, KCl, AA and LA against the test strains were 2,5-10 μL.mL-1, 200 mg.mL-1, 300 mg.mL-1, 2,5 μL.mL-1e 10 μL.mL-1, respectively. After the exposure of the strains to sublethal concentrations (½ MIC and ¼ MIC) of OVEO, MIC values of this essential oil against the habituated cells were maintained the same or decreased up to five-fold when compared to the non-habituated cells, revealing no induction of direct tolerance. The OVEO not induced the development of cross-tolerance to NaCl, KCl, AA and LA, since the MIC values of these antimicrobials against test strains habituated to sublethal amounts (½ MIC and ¼ MIC) of OVEO were the same or up to six-fold lower when compared to those obtained against the non-habituated cells. These data suggest that sublethal concentrations of OVEO can be applied in food preservation safely, since this essential oil did not induced direct tolerance or cross-tolerance to the tested S. aureus strains.