PPGBIO - Dissertações de mestrado
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- ItemAtividade antimicrobiana e antibiofilme da epigalocatequina galato em Staphylococcus aureus(Universidade Federal do Espírito Santo, 2018-03-06) Knidel, Carina; Schuenck, Ricardo Pinto; Guimarães, Marco César Cunegundes; Silva, André Romero daBacterial infections are among the major public health problems and the emergence of antimicrobial resistant bacteria becomes increasingly common. Staphylococcus aureus is an opportunistic pathogen, can cause a variety of infections, both hospital and community. Epigallocatechin gallate (EGCG), a flavonoid present in the leaves of the plant of Camelia sinensis, has different biological activities, including antimicrobial potential. The objective of the present study was to evaluate the antimicrobial, in vitro and in vivo, and antibiofilm potentials of EGCG in clinical S. aureus isolates with different genetic backgrounds. Nine strains isolated from different infections and with different antimicrobial susceptibilities were used. The antimicrobial activity was performed by broth microdilution test to determine the minimum inhibitory concentration (MIC) and the time-kill curve test. The MIC results ranged from 7.81 to 62.5 μg/mL and bactericidal activity was observed with 4 times the MIC. The activity of antibiofilm was evaluated after incubation of the isolates in the presence and absence of EGCG. Sub-inhibitory concentrations were able to significantly inhibit S. aureus biofilm production. The largest reduction in biofilm production was 100% and the smallest reduction among 50-60%. Cytotoxicity assays showed that concentrations ≤ 62.5 μg/mL EGCG were non-cytotoxic to murine macrophages. Regarding the in vivo test with G. mellonella larvae, EGCG significantly reduced the mortality of larvae infected by this pathogen (P = 0.0005) in only one isolate. In general, EGCG showed efficacy in inhibiting the growth of different clinical isolates of S. aureus and exhibited a relevant property of antibiofilm. Thus, EGCG is a promising substance for the treatment of infections caused by S. aureus.
- ItemEstudo in silico de derivados do G-CSF humano como antibacterianos(Universidade Federal do Espírito Santo, 2013-07-31) Saturnino, Christine Facco; Guimarães, Marco Cesar Cunnegundes; Juliano, Maria Aparecida; Gomes, Daniel Claúdio de OliveiraIn attempt to obtain new substances with antibacterial activity, the aim of this study was to evaluate the antibacterial potential of four synthesized peptides, where two of them have sequence derived from human G-CSF in silico fragmentation, while the other two were theoretically planned, allowing the verification of their interest as new therapeutic agents at human health. The evaluation was performed in two stages: in silico analysis, consisting of predictions of properties and parameters associated with antibacterial effect, through computational tools; and the in vitro experiment for determination of the minimum inhibitory concentration (MIC) of the peptides against Gram positive and negative bacteria. Most predictions was favorable for all four peptides, showed by determined results of hydrophobicity, amphipathicity, size, secondary structure, net charge, membrane binding potential, half-life and Boman Index, considered as desirable values for antibacterial potential. In the in silico analysis, only algorithmic prediction of antimicrobial activity revealed unfavorable results for peptides with sequences derived from G-CSF (peptides 1 and 2), nonetheless, the predictions were positive for the other two. The in vitro assay showed that up to the highest concentration used of the four peptides (500 μg/mL) was insufficient for determination of minimum inhibitory concentration, however it was possible to observe significant growing decrease of E. coli (58.7%) by peptide 4 and E. fecalis (86.1%) and E. coli (54.9%) by peptide 3, when compared with the viability control. These values indicate the presence of antibacterial activity in the theoretically planned peptides (peptides 3 and 4), confirming the computational predictions. Thus, it is possible to conclude that the in silico analysis was very important for the selection of the peptides to be synthesized, which showed results of in vitro assays in agreement with the computational prediction of antimicrobial activity.