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    Antibiotic adjuvant activities of quorum sensing signal molecules DSF and BDSF against mature biofilms of Staphylococci
    (Taylor & Francis, 2024) Bilgin, Merve; Döşler, Sibel; Ötük, Gülten
    Among promising antibiofilm compounds, quorum-sensing (QS) molecules that regulate biological processes such as biofilm formation and intra- or interspecies communication appear to be good candidates. The invitro antibiotic-adjuvant effects of QS molecules diffusible signal factor (DSF) and B. cenocepacia producing-DSF (BDSF) were investigated against mature Staphylococcal biofilms. Broth microdilution methods were used for the determinations of MIC, MBC, MBIC, and MBEC, and bactericidal activities were determined by TKC method. The lowest MICs were obtained with ciprofloxacin and gentamicin, and MBECs with ciprofloxacin. DSF and BDSF at 0.5 µM decreased the MICs as 2–8, and 2–32 fold, respectively. In TKC studies, –cidal activities were achieved by BDSF + gentamycin, or ciprofloxacin, and DSF + daptomycin, vancomycin, meropenem or gentamycin combinations. Synergistic effects were generally obtained with BDSF + gentamicin combinations, followed by DSF + daptomycin against most S. aureus; while BDSF + gentamicin or ciprofloxacin, and DSF + vancomycin or meropenem were synergist against some S. epidermidis biofilms. Also, the antagonist effects were observed with BDSF + meropenem or ciprofloxacin against each MSSE and MSSA. It is estimated that these QS molecules, although it was strain dependent, generally enhanced the antibiotic activity, and would be a new and effective treatment strategy for biofilm control, either alone or as an antibiotic adjuvant.
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    Antimicrobial activity of pulicaria species from Turkey
    (İstanbul Üniversitesi Yayınları, 2021) Özdemir Nath, Ebru; Bilgin, Merve; Gürdal, Bahar
    Objective: In traditional medicine, the Pulicaria species are used for various disorders such as inflamed wounds, skin diseases, and bronchitis. This study investigated the antibacterial effect of five Pulicaria species in Turkey; (Pulicaria (P) arabica (L.) Cass., P. dysenterica (L.) Bernh., P. odora (L.) Reichb., P. sicula (L.) Moris, P. vulgaris (L.) Gaertn.) against certain significant pathogenic gram-negative and gram-positive reference bacteria. Material and Method: Four extracts (decoction, infusion, aqueous, and ethanol (EtOH) extracts) were prepared from the Pulicaria species. The antimicrobial activity of the samples was examined against reference organisms; Bacillus (B) subtilis, Enterococcus faecalis, Escherichia coli, Klebsiella pneumoniae, Methicillin-resistant Staphylococcus (S) aureus (MRSA), Proteus mirabilis, S. aureus and Pseudomonas aeruginosa. The minimal bactericidal concentration (MBC) and minimum inhibitory concentration (MIC) ranges of the extract samples were demonstrated based on a microbroth dilution method. Results: The EtOH extracts of the studied four Pulicaria species were found to be weakly active against gram-positive bacteria such as B. subtilis, MRSA and S. aureus but the EtOH extract of P. dysenterica showed exceptionally good activity against the reference strains of S. aureus, MRSA. No antimicrobial activity was detected in the infusion, decoction, and aqueous extracts. Conclusion: The Pulicaria species, especially P. dysenterica could be evaluated as antimicrobial agents. Further studies with the extracts and essential oils from Pulicaria sp. on other bacteria and pathogenic fungi should be performed.
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    Synthesis, characterization and biological evaluation of 1,3-thiazolidine-4-ones derived from (2S)-2-benzoylamino-3-methylbutanohydrazide hydrazones
    (Marmara University Press, 2021) Tatar, Esra; Küçükgüzel, İlkay; Ötük, Gülten; Bilgin, Merve; De Clercq, Erik; Andrei, Graciela; Snoeck, Robert; Pannecouque, Christophe; Kaushik-Basu, Neerja
    Novel 2-aryl-5-non-substituted / methyl-1,3-thiazolidine-4-one derivatives 14-33 carrying L-valine core were synthesized by the reaction of acylhydrazones 4-13 with thioglycolic acid / thiolactic acid. Structures of all synthesized compounds 14-33 were confirmed by IR, H-1-NMR and HR-MS analysis and C-13-NMR were recorded for selected compounds 17, 21, 28 and 30. None of the compounds 14-33 showed activity against HIV-1 (strain IIIB) or HIV-2 (strain ROD) in an MT-4/MTT based assay. Compounds 14-33 were also screened against Feline Corona Virus (FIPV), Feline Herpes Virus, HSV-1(KOS), HSV-1 (TK-KOS ACVr), HSV-2 (G), Vaccinia virus, Vesicular stomatitis virus, Cytomegalovirus, Varicella-Zoster virus, Respiratory syncytial virus, Coxsackie B4 virus, Parainfluenza-3 virus, Reovirus-1, Sindbis virus and Punta Toro virus, but none of them showed antiviral activity at subtoxic concentrations. Anti-HCV NS5B RdRp activity of some selected compounds from the series 14-33 were found to vary between 4.1-27 % at the concentration of 100 mu M. In vitro antibacterial activity evaluation of selected compounds 16-23 and 25-32, against Staphylococcus aureus ATCC 25923, Escherichia coli ATCC 25922, Pseudomonas aeruginosa ATCC 27853, Enterococcus faecalis ATCC 29212, Klebsiella pneumoniae ATCC 4352, Bacillus subtilis ATCC 6633, Staphylococcus epidermidis ATCC 12228, MRSA and antifungal activity against Candida albicans ATCC 10231 resulted in the MIC values between 625->5000 mu g/ml.