Investigation of antibacterial and antipathogenic activities of certain compounds with natural origin from terpenes and phenolics on Proteus mirabilis
Project no. 339 · Status: Kapanmış · 2018
Summary
In this study, it was aimed to investigate the antibacterial and anti-pathogenic effects of some phytochemicals from terpenes and phenolics against Proteus mirabilis, a typical uropathogen. In this context, minimum inhibitory concentrations (MIC) of alpha-terpineol, bisabolol, decanol, farnesol, hederasaponin, carvacrol, quercetin, eugenol, eucalyptol, cinnamaldehyde, terpinen-4-ol, and thymol were determined in clinical isolates of P. mirabilis isolated in Ege University Medical Faculty Medical Microbiology Department Bacteriology Laboratory and P. mirabilis HI4320 reference strain from Mobley Research Laboratories (Ann Arbor, USA). The combined effects of these compounds and some antibiotics used in urinary tract infections (UTIs) were then examined using the checkerboard method. Also, the effects of related compounds on the formation of swarming motility, urease expression and biofilm formation of the reference strain were investigated. Genotypic effects of inhibitory compounds on expression levels of flaA, flhD, glnA, hisG, mrpJ, ompF, rcsB, rcsD, rpoA, speB, umoC ve ureD, which involved in the regulation of virulence factors, were also examined by RT-qPCR. In addition, the mechanism of action is examined in more detail by observing the changes in the effect of inhibitor compounds on clones generated by reference strain and expressing high levels of some selected genes. Compounds showing the strongest antimicrobial activity are carvacrol (128-256 µg/ml), cinnamaldehyde (256-512 µg/ml) and thymol (128-512 µg/ml) according to the MIC values determined by microdilution method. However, no synergistic effect was observed at any concentration between antibiotics and compounds in combination studies. It has been shown that carvacrol, quercetin, cinnamaldehyde, and thymol inhibit the swarming motility in a dose-dependent manner. Furthermore, cinnamaldehyde has been found to be a dose-dependent inhibitör against urease expression. Carvacrol and thymol, which suppress the swarming motility, caused inhibition in the production of biofilms, although quercetin and cinnamaldehyde cause activation. When the effects of these compounds on the expression levels of selected genes were assessed, their effects were different depending on the form of the medium. It has been found that clones over-expressing flhC, speB and ompF has been found to be able to swarm at the same level with the control group by compensating for inhibition caused by quercetin. Carvacrol, quercetin, cinnamaldehyde and thymol, compounds of our project, significantly inhibited the virulence factors of P. mirabilis in vitro. These compounds can be effective against other uropathogens, as well as P. mirabilis, which often leads to polymicrobial infections. Although thymol and carvacrol are generally toxic, quercetin and cinnamaldehyde have very low toxicity. These compounds, which are used as food or in phytotherapy, are widely available in various plants. Given these advantages, it is foreseen that the relevant compounds may be utilized in the UTIs prophylaxis. Thus, by reducing the number of antibiotics used, economic gains can be gained, and the development of resistance can be reduced to a certain extent. In addition, molecular methods such as RT-qPCR and cloning experiments, which are used in the scope of the project, are thought to contribute positively to the quality of the study and are expected to make publications in international journals more interesting.