Person: AKSU, MEHMET BURAK
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AKSU
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MEHMET BURAK
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Publication Open Access Phenolic compounds affect production of pyocyanin, swarming motility and biofilm formation of Pseudomonas aeruginosa(WOLTERS KLUWER MEDKNOW PUBLICATIONS, 2016-08) KARAHASAN, AYŞEGÜL; Ugurlu, Aylin; Yagci, Aysegul Karahasan; Ulusoy, Seyhan; Aksu, Burak; Bosgelmez-Tinaz, GulgunObjective: To investigate the effects of plant-derived phenolic compounds (i.e. caffeic acid, cinnamic acid, ferulic acid and vanillic acid) on the production of quorum sensing regulated virulence factors such as pyocyanin, biofilm formation and swarming motility of Pseudomonas aeruginosa (P. aeruginosa) isolates. Methods: Fourteen clinical P. aeruginosa isolates obtained from urine samples and P. aeruginosa PA01 strain were included in the study. The antibacterial effects of phenolic compounds were screened by well diffusion assay. Pyocyanin and biofilm activity were measured from culture supernatants and the absorbance values were measured using a spectrophotometer. Swarming plates supplemented with phenolic acids were point inoculated with P. aeruginosa strains and the ability to swarm was determined by measuring the distance of swarming from the central inoculation site. Results: Tested phenolic compounds reduced the production of pyocyanin and biofilm formation without affecting growth compared to untreated cultures. Moreover, these compounds blocked about 50% of biofilm production and swarming motility in P. aeruginosa isolates. Conclusions: We may suggest that if swarming and consecutive biofilm formation could be inhibited by the natural products as shown in our study, the bacteria could not attach to the surfaces and produce chronic infections. Antimicrobials and natural products could be combined and the dosage of antimicrobials could be reduced to overcome antimicrobial resistance and drug side effects.Publication Open Access Performance of “RESIST-3 O.K.N. K-SeT” immunochromatographic assay for the detection of OXA-48 like, KPC, and NDM carbapenemases in Klebsiella pneumoniae in Turkey(2018-10) ALTINKANAT GELMEZ, GÜLŞEN; Sağıroğlu, Pınar; Hasdemir, Ufuk; Altınkanat Gelmez, Gülşen; Aksu, Burak; Karatuna, Onur; Söyletir, GünerPublication Metadata only Group B Streptococci Induce Interleukin 8 Production in Human Cervical Epithelial Cell Cultures: The Role of Capsule Polysaccharide(MARMARA UNIV, INST HEALTH SCIENCES, 2019) AKSU, MEHMET BURAK; Aksu, Burak; Yanilmaz, OzgurObjective: Group B streptococci (GBS) are the major cause of pneumonia, sepsis, and meningitis in neonates and adults. Epithelial invasion and early cytokine response of female genital tract considered to be important in the pathogenesis of GBS infection. In this study, we studied the IL-8 induction in cervical epithelial cells in response to stimulus with encapsulated (COH1) and unencapsulated (COH1-13) strains of group B streptococci. Methods: Human cervical epithelial cell (HeLa) cultures were stimulated with different concentrations (10(6) CFU/ml and 10(8) CFU/ml) of two GBS strains. E.coli LPS was used as positive control and at specified time points (4, 8 and 24 hour) cell culture supernatant samples were collected. IL-8 level in samples was quantified by using ELISA assay. Results: Both GBS strains caused an equal IL-8 response in HeLa cells in a time-dependent manner. In addition, cytokine levels triggered by different bacterial concentrations were similar and comparable with LPS. Conclusion: Our study showed that GBS induce proinflammatory IL-8 levels in cervix epithelial cells. This induction seems to be independent from capsule polysaccharides and suggesting that other bacterial components are involved in IL-8 stimulation.Publication Open Access Catheter-related Saccharomyces cerevisiae Fungemia Following Saccharomyces boulardii Probiotic Treatment: In a child in intensive care unit and review of the literature(2017-03) KIYAN, GÜRSU; Atıcı, Serkan; Soysal, Ahmet; Karadeniz Cerit, Kıvılcım; Yılmaz, Şerife; Aksu, Burak; Kıyan, Gürsu; Bakır, MustafaPublication Metadata only Synthesis of 1,4-diazabicyclo[2.2.2]octane and pyridinium based cationic polymers via ROMP technique and examination of their antibacterial activity and cytotoxicity(ELSEVIER SCI LTD, 2019) SEZER, ALİ DEMİR; Kaymaz, Aylin Pak; Acaroglu-Degitz, Ilayda; Yapaoz, Melda Altikatoglu; Sezer, Ali Demir; Malta, Seyda; Aksu, Burak; Eren, TarikThis paper focuses on the synthesis of cationic antibacterial polymers that could be a potential source for new-generation antibiotics with well-defined architecture derived from the Ring Opening Metathesis Polymerization (ROMP) technique. Mono- and double-charge bearing quaternary groups have been used to synthesize cationic homopolymers (MWs: 3000 and 10,000 g/mole) and their copolymers (MWs: 5000 g/mole). Hemolytic concentration (HC50, >= 1000 mu g/mL) and MTS assay results showed that the polymers are non-toxic. It has been observed that the double-charge bearing polymers have the highest antimicrobial activity (S. aureus= 8 mu g/mL) and a high selectivity against S. aureus (>250). Percent killing efficiencies were tested on a glass surface where moderate killing efficiency was observed in the range of 40-80% in 5 min. Cationic charge density and zeta potential studies were used to investigate the mechanisms of antimicrobial efficiency of the polymers in a solution during the action against S. aureus to understand structure-activity relationships. Scanning electron microscopy (SEM) was also conducted for the bacterial morphology assay.Publication Metadata only The relationship between macrolide resistance mechanisms and serotypes of streptococcus pneumoniae(2012-01-01) AKSU, MEHMET BURAK; HASDEMİR GÖKBOĞA, MÜNEVVER UFUK; Tiryakioglu N., AKSU M. B., HASDEMİR GÖKBOĞA M. U.Objective: Increased resistance rate to macrolides used as empirical treatment of pneumococcal infections is a major problem in our country and all over the world. In our study, we aimed to determine macrolide resistance mechanisms of the erythromycin-resistant Streptococcus pneumonia isolated from clinical samples and to investigate serotype and resistance relationship within our region with the high macrolide resistance rates among pneumococci.Publication Metadata only Effect of extremely low frequency electromagnetic fields on bacterial membrane(TAYLOR & FRANCIS LTD, 2016) GARİP, GÜNSELİ AYŞE; Oncul, Sule; Cuce, Esra M.; Aksu, Burak; Garip, Ayse InhanPurpose: The effect of extremely low frequency electromagnetic fields (ELF-EMF) on bacteria has attracted attention due to its potential for beneficial uses. This research aimed to determine the effect of ELF-EMF on bacterial membrane namely the membrane potential, surface potential, hydrophobicity, respiratory activity and growth.Materials and methods: Gram-positive Staphylococcus aureus and Gram-negative Escherichia coli were subjected to ELF-EMF, 50Hz, 1mT for 2h. Membrane potential was determined by fluorescence spectroscopy with or without EDTA (Ethylenediaminetetraacetic acid) with DisC3(5) (3,3-dipropylthiacarbocyanine iodide), zeta potential measurements were performed by electrophoretic mobility, hydrophobicity of the membrane was measured with MATH (Microbial Adhesion to Hydrocarbons) test, respiratory activity was determined with CTC (5-Cyano-2,3-ditolyl tetrazolium chloride), colony forming unit (CFU) and DAPI (4,6-diamidino-2-phenylindole, dihydrochloride) was used for growth determinations.Results: ELF-EMF caused changes in physicochemical properties of both Gram-positive and Gram-negative bacteria. Hyperpolarization was seen in S. aureus and EDTA-treated E. coli. Surface potential showed a positive shift in S. aureus contrariwise to the negative shift seen in EDTA-untreated E. coli. Respiratory activity increased in both bacteria. A slight decrease in growth was observed.Conclusion: These results show that ELF-EMF affects the crucial physicochemical processes in both Gram-positive and Gram-negative bacteria which need further research.Publication Metadata only Evaluation of 2015-2016 MOTAKK HBV DNA and HCV RNA External Quality Assessment National Program Results(ANKARA MICROBIOLOGY SOC, 2018) AKSU, MEHMET BURAK; Karatayli, Ersin; Soydemir, Ege; Aksoy, Zeynep Busra; Kizilpinar, Mehtap; Altay Kocak, Aylin; Karatayli, Senem Ceren; Yurdcu, Esra; Yildirim, Umut; Guriz, Haluk; Bozdayi, Gulendam; Yurdaydin, Cihan; Ilhan, Osman; Yildirim, Yasin; Bozdayi, A. Mithat; Oguz, Acelya Yalcintas; Baris, Ahmet; Alp, Alpaslan; Aksozek, Alper; Sayiner, Arzu; Karagul, Aydan; Ordu, Aylin; Istanbullu, Aye; Otlu, Baris; Aridogan, Buket; Aksu, Burak; Buruk, C. Kurtulus; Karahan, Ceren; Guney, Cakir; Toksoz, Devrim; Yildirim, Dilara; Colak, Dilek; Daglar, Duygu Eren; Findik, Duygu; Kas, Elif; Caliskan, Emel; Zeyrek, Fadile Yildiz; Arslan, Fatma; Demir, Feyza; Milletli, Fikriye; Kibar, Filiz; Ozdincer, Furkan; Dundar, Gulnur; Arslan, Hande; Agca, Harun; Aliskan, Hikmet Eda; Guducuoglu, Huseyin; Fidan, Isil; Akyar, Isin; Afsar, Ilhan; Kaleli, Ilknur; Donmez, Ismail; Yanik, Kemalettin; Midilli, Kenan; Cubukcu, Kivanc; Ozdemir, Mehmet; Acar, Melek; Yalinay, Meltem; Kuskucu, Mert Ahmet; Bakici, Mustafa Zahir; Aydin, Neriman; Yilmaz, Neziha; Ceken, Nihan; Ziyade, Nihan; Yilmaz, Nisel; Ozgumus, Osman Birol; Gitmisoglu, Ozlem; Demirgan, Recep; Kesli, Recep; Guckan, Ridvan; Sertoz, Ruchan; Akgun, Sadik; Aksaray, Sebahat; Tezcan, Seda; Kaygusuz, Sedat; Gokahmetoglu, Selma; Mese, Sevim; Bayik, Seyit Ahmet; Akcali, Sinem; Gurcan, Saban; Karsligil, Tekin; Us, Tercan; Ozekinci, Tuncer; Pilgir, Tulin; Aslan, Ugur; Dinc, Ugur; Coskun, Umut Safiye Say; Cetinkol, Yeliz; Keskin, Yusuf; Ayaydin, Zeynep; Toraman, Zulal AsciMOTAKK, as a national external quality control program has been launched to evaluate the molecular detection of viral infections including HBV DNA and HCV RNA in molecular microbiology diagnostic laboratories in Turkey. This program is prepared in compliance with ISO 17043:2010 (Conformity assessment general requirements for proficiency testing) standards, and aims to take the place of external quality control programs from abroad, contributing to standardization and accuracy of molecular diagnostic tests in our country. The aim of this study was to evaluate 2015 and 2016 results of the MOTAKK External Quality Control Program for HBV DNA and HCV RNA viral load. The calls were announced on the web page of MOTAKK (www.motakk.org). The quality control samples were sent to participating laboratories in 2015 and 2016. Main stocks were prepared from patients with chronic hepatitis B and C who had viral load detection with reference methods according to WHO reference materials for viral load studies to improve quality control sera. From these main stocks, samples with different viral loads were prepared from dilutions of plasma with HBV, HCV, HAV, HIV, Parvovirus B19 and CMV negative serologic markers. Quality control samples were sent to the participating laboratories along with the negative samples in the cold chain. The laboratories accomplished the related tests within 2-3 weeks and entered their results on the MOTAKK web page. These results were analysed according to ISO 13528 (Statistical methods for use in proficiency testing by interlaboratory comparison) and scoring reports were created by a software developed by MOTAKK and sent to participating labs. Each laboratory evaluated their own results in comparison with the other laboratory results, reassessed the tests via observing the distance from the mean result and the reference values. The number of laboratories participating in the HBV DNA and HCV RNA external quality control program was 70-73 in 2015-2016. Participants were able to comply with the program tools, registering, entering results and receiving the results reports problem. In HBV panel, 72.6-89.1% and 84.7-90.3% of the participant laboratories were in 1 standard deviation (SD) in 2015-2016, respectively. In HCV panel, 70.8-89.1% and 84.7-90.3% of the participant laboratories were in 1 SD in 2015-2016, respectively. A national external quality control program for HBV DNA and HCV RNA in Turkey has been prepared for the first time with this project and implemented successfully. All the data provided in the MOTAKK external quality control program final report, compensate all the data provided by the quality control program final reports from abroad; additionally, the report allows comparison of used technologies and commercial products.Publication Unknown Effect of extremely low frequency electromagnetic fields on growth rate and morphology of bacteria(TAYLOR & FRANCIS LTD, 2011) ÖZAYDIN, AYŞE NİLÜFER; Inhan-Garip, Ayse; Aksu, Burak; Akan, Zafer; Akakin, Dilek; Ozaydin, A. Nilufer; San, TangulPurpose: To determine the effect of extremely low frequency (<300 Hz) electromagnetic fields (ELF-EMF) on the growth rate of Gram-positive and Gram-negative bacteria and to determine any morphological changes that might have been caused by ELF-EMF. Materials and methods: Six bacterial strains, three Gram-negative and three Gram-positive were subjected to 50 Hz, 0.5 mT ELF-EMF for 6 h. To determine growth rate after ELF-EMF application, bacteria exposed to ELF-EMF for 3 h were collected, transferred to fresh medium and cultured without field application for another 4 h. Growth-rate was determined by optical density (OD) measurements made every hour. Morphological changes were determined with Transmission electron microscopy (TEM) for two gram-negative and two gram-positive strains collected after 3 h of field application. Results: A decrease in growth rate with respect to control samples was observed for all strains during ELF-EMF application. The decrease in growth-rate continued when exposed bacteria were cultured without field application. Significant ultrastructural changes were observed in all bacterial strains, which were seen to resemble the alterations caused by cationic peptides. Conclusion: This study shows that ELF-EMF induces a decrease in growth rate and morphological changes for both Gram-negative and Gram-positive bacteria.Publication Unknown Evaluation of geneXpert MTB/RIF test performance for respiratory and nonrespiratory clinical samples(2014-05-12) İLKİ, ZEYNEP ARZU; AKSU, MEHMET BURAK; İlki Z. A., Aksu M. B., Ayaş R., Söyletir G.