Atividade antibacteriana e anti-enterotoxinas de compostos fenólicos sobre bactérias de interesse clínico
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Data
2016-07-18
Autores
Albano, Mariana [UNESP]
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Editor
Universidade Estadual Paulista (Unesp)
Resumo
As doenças infecciosas, incluindo aquelas transmitidas por alimentos, causadas por micro-organismos ainda representam uma grande preocupação, especialmente devido ao surgimento de bactérias resistentes aos antimicrobianos atualmente em uso. Várias substâncias provenientes de plantas exibem atividades inibitórias sobre micro-organismos, sendo uma estratégia empregada para buscas de novos fármacos que interfiram nos mecanismos de resistência. O objetivo deste estudo foi avaliar o efeito inibitório de cinco compostos voláteis majoritários encontrados em óleos essenciais de algumas plantas (eugenol, cinamaldeído, terpineol, geraniol e citronelol) sobre bactérias Gram-positivas e Gram-negativas (padrões ATCC e isolados clínicos) para determinação da Concentração Inibitória Mínima (CIM) pela metodologia da microdiluição (Resazurin Microtiter Assays-REMA). Além disto, foram testadas combinações entre os compostos e drogas antimicrobianas de uso convencional para verificação de sinergismo e a influência de concentrações subinibitórias dos compostos na produção de enterotoxinas estafilococócicas dos tipo A, B, C e D. A fim de ilustrar o efeito dessas substâncias nas células bacterianas de E. coli e MRSA e na formação do septo divisional em X. citri, foram feitas imagens por microscopia eletrônica de transmissão (MET) e microscopia de fluorescência, respectivamente. O composto que apresentou melhor atividade antimicrobiana sobre as linhagens bacterianas testadas foi o cinamaldeído com valores ao redor de 100 – 400 µg/mL. As combinações que apresentaram melhores efeitos sinérgicos foram aquelas contendo gentamicina. Terpineol e geraniol inibiram a produção de enterotoxina B e todos os compostos testados inibiram a produção de enterotoxina C, enquanto que a produção das enterotoxinas A e D não foram influenciadas. As imagens obtidas através da microscopia eletrônica demonstraram danos na parede celular das bactérias causados pela ação dos compostos cinamaldeído e eugenol. Nas imagens obtidas por meio da microscopia de fluorescência, nas bactérias cultivadas com cinamaldeído e carvacrol não há sinais de septação após 1 hora de tratamento. De acordo com os resultados obtidos, os compostos testados apresentam ação antimicrobiana, o que os habilita para potenciais agentes na elaboração de fármacos com finalidade de uso na terapêutica de doenças infecciosas.
Infectious diseases caused by microorganisms, including those transmitted by food, still represent a major concern especially due to the emergence of bacteria resistant to antibiotics currently in use. Several plant extracts have exhibited activity against microorganisms, and this is a strategy used to search for new drugs to combat the mechanisms of resistance. The aim of this study was to evaluate the inhibitory effect of five majority phenolic compounds found in essential oils (eugenol, cinnamaldehyde, terpineol, geraniol and citronellol) on Gram-positive and Gram-negative bacteria (ATCC standards and clinical isolates) to determine the Minimum inhibitory Concentration (MIC) by Resazurin Microtiter Assays (REMA). Furthermore, combinations between the compounds and antimicrobial agents were tested by disc diffusion method (Kirby & Bauer) and time kill assays, and the influence of subinhibitory concentrations of the compounds in the production of staphylococcal enterotoxins types A, B, C and D. In order to illustrate the effect of these substances on bacterial cells of E. coli and MRSA and the formation of divisional septal X. citri, images were obtained by transmission electron microscopy (TEM) and fluorescence microscopy, respectively. The compound that showed better antimicrobial activity against the tested bacterial strains was cinnamaldehyde, with values around 100-400 ug/mL. The combinations that showed better synergistic effects were those containing gentamicin. Terpineol and geraniol inhibited the production of enterotoxin B and all compounds tested inhibited the production of enterotoxin C, while the production of enterotoxins A and D were not influenced. The images obtained by electron microscopy showed damage in the cell wall of bacteria caused by the action of cinnamaldehyde and eugenol. X. citri grown with carvacrol and cinnamaldehyde showed no signs of septation after 1 hour of treatment. According to the results, the tested compounds have antimicrobial activity, which enables them to potential agents in the preparation of drugs with the purpose of use in therapy of infectious diseases.
Infectious diseases caused by microorganisms, including those transmitted by food, still represent a major concern especially due to the emergence of bacteria resistant to antibiotics currently in use. Several plant extracts have exhibited activity against microorganisms, and this is a strategy used to search for new drugs to combat the mechanisms of resistance. The aim of this study was to evaluate the inhibitory effect of five majority phenolic compounds found in essential oils (eugenol, cinnamaldehyde, terpineol, geraniol and citronellol) on Gram-positive and Gram-negative bacteria (ATCC standards and clinical isolates) to determine the Minimum inhibitory Concentration (MIC) by Resazurin Microtiter Assays (REMA). Furthermore, combinations between the compounds and antimicrobial agents were tested by disc diffusion method (Kirby & Bauer) and time kill assays, and the influence of subinhibitory concentrations of the compounds in the production of staphylococcal enterotoxins types A, B, C and D. In order to illustrate the effect of these substances on bacterial cells of E. coli and MRSA and the formation of divisional septal X. citri, images were obtained by transmission electron microscopy (TEM) and fluorescence microscopy, respectively. The compound that showed better antimicrobial activity against the tested bacterial strains was cinnamaldehyde, with values around 100-400 ug/mL. The combinations that showed better synergistic effects were those containing gentamicin. Terpineol and geraniol inhibited the production of enterotoxin B and all compounds tested inhibited the production of enterotoxin C, while the production of enterotoxins A and D were not influenced. The images obtained by electron microscopy showed damage in the cell wall of bacteria caused by the action of cinnamaldehyde and eugenol. X. citri grown with carvacrol and cinnamaldehyde showed no signs of septation after 1 hour of treatment. According to the results, the tested compounds have antimicrobial activity, which enables them to potential agents in the preparation of drugs with the purpose of use in therapy of infectious diseases.
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Palavras-chave
Óleos essenciais, Bactérias patogênicas, Ação antimicrobiana, Enterotoxinas, Sinergismo, Essential oils, Phenolic compounds, Pathogenic bacteria, Antimicrobial action, Synergism, Enterotoxina