GCRIS

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Investigation of Molecular Effect of Phenolic Acids on Methicillin-Resistant and Methicillin-Susceptible Staphylococcus Aureus in Comparison To Their Phenolic Acid Resistant Mutants
(Izmir Institute of Technology, 2018) Keman, Deniz; Soyer, Ferda
Staphylococcus aureus is a Gram-positive bacterium whose acquisition through an open wound results in various infections. Methicillin-resistant S. aureus (MRSA) and methicillin-susceptible S. aureus (MSSA) strains are responsible for diseases ranging from soft tissue infections to fatal pneumonia which cannot be treated due to multiple drug-resistances of these strains. This situation increases the importance of searching for alternative antimicrobials worldwide. Having all these in mind, the capacity of phenolic acids cannot be denied to be used against pathogenic bacteria. Phenolic acids produced as plant secondary metabolites show antibacterial effects besides many beneficial properties for human health. The aim of this study was to investigate the antibacterial action mechanisms of vanillic acid and 2-hydroxycinnamic acid on MRSA and MSSA. To achieve this, firstly the antibacterial effects of phenolic acids on both bacteria were investigated by determination of minimum inhibitory concentrations. Then, the resistance development ability of bacteria against phenolic acids was tested by continuous exposure to subinhibitory concentrations. Finally, the action mechanisms of phenolic acids on bacteria were elucidated using two different proteomic approaches. According to the results, bacteria were not able to develop resistance against phenolic acids. Proteomic studies displayed alterations in the protein profiles of phenolic acid treated bacteria and provided potential targets in the battle with pathogenic bacteria. By showing the inability of MRSA and MSSA to develop resistance to phenolic acids and the important proteomic alterations that are induced by phenolic acid treatment, this study highlights the significance of phenolic acids to be used against antibiotic-resistant bacteria.
Detection of Staphylococcus Aureus Using Quqntitative Real-Time Polymerase Chain Reaction and Loop-Mediated Isothermal Amplification Methods in Turkish White Cheese
(Izmir Institute of Technology, 2013) Kadiroğlu, Pınar; Korel, Figen
The aim of this study was to utilize the quantitative real-time polymerase chain reaction (qPCR) method for direct quantitative detection of S. aureus in Turkish white cheese samples and identification of the isolated colonies using phenotypic and molecular methods. The TaqMan and LNA probe-based qPCR analyses were compared by targeting the nuc gene of S. aureus cells to improve the performance of qPCR analyses to quantify low levels of S. aureus cells. TaqMan probe-based assay was found to be more sensitive than LNA probe based assay in S. aureus pure culture and artificially contaminated white cheese sample studies. For direct bacterial DNA extraction from cheese samples, four different methods were compared. The detection range of S. aureus quantification was improved down to 13.2 CFU/g with the combined DNA extraction method of using trypsin and the food DNA extraction kit in artificially contaminated cheese samples. In the naturally contaminated cheese samples, the bacterial numbers calculated by the qPCR method were higher than the plate counts which can be related to detection of live and dead cells together. Loop-mediated isothermal amplification (LAMP) method was found to have some weak points in giving consistent results with lower efficiency value for detection of S. aureus. In the identification part of the study, 207 pure cultures were obtained. Among the 24 phenotypically and genotypically characterized isolates, 3 isolates were found to be S. aureus according to the sequence analyses of the 16S ribosomal DNA genomic region.

Phd Degree / Doktora

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