Person: KARAHASAN, AYŞEGÜL
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KARAHASAN
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AYŞEGÜL
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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 Analysis of quorum sensing-dependent virulence factor production and its relationship with antimicrobial susceptibility in Pseudomonas aeruginosa respiratory isolates(ELSEVIER SCI LTD, 2010-12) KARAHASAN, AYŞEGÜL; Karatuna, O.; Yagci, A.P>Pseudomonas aeruginosa is an opportunistic pathogen causing severe respiratory infections. The pathogenesis of these infections is multifactorial and the production of many virulence factors is regulated by quorum sensing (QS), a cell-to-cell communication mechanism. The two well defined QS systems in P. aeruginosa, the las and rhl systems, rely on N-acyl homoserine lactone signal molecules, also termed autoinducers. We assessed the activity of QS-dependent virulence factors (including elastase, alkaline protease, pyocyanin and biofilm production) in respiratory isolates of P. aeruginosa and their relationship with antimicrobial susceptibility. We identified sixteen isolates displaying impaired phenotypic activity; among them, eleven isolates were also defective in autoinducer production, and therefore considered QS-deficient. Six of the QS-deficient isolates failed to amplify one or more of the four QS regulatory genes (lasI, lasR, rhlI, rhlR) with PCR: one isolate was negative for rhlR, two isolates were negative for rhlI and rhlR and three isolates were negative for all four genes. The isolates that were negative for virulence factor production were generally less susceptible to the antimicrobials and statistically significant correlations were observed between the lack of elastase production and resistance to piperacillin and ceftazidime; between failure in alkaline protease production and resistance to tobramycin, piperacillin, piperacillin-tazobactam, cefepime, imipenem and ciprofloxacin; and between failure in pyocyanin production and resistance to amikacin, tobramycin, ceftazidime, ciprofloxacin and ofloxacin. The results obtained indicate that, despite the pivotal role of QS in the pathogenesis of P. aeruginosa respiratory infections, QS-deficient strains are still capable of causing infections and tend to be less susceptible to antimicrobials.Publication Open Access Prevalence of Rotavirus Genotypes in Children Younger than 5 Years of Age before the Introduction of a Universal Rotavirus Vaccination Program: Report of Rotavirus Surveillance in Turkey(2014-12-01) KARAHASAN, AYŞEGÜL; Durmaz, Riza; Kalaycioglu, Atila Taner; Acar, Sumeyra; Bakkaloglu, Zekiye; Karagoz, Alper; Korukluoglu, Gulay; Ertek, Mustafa; Torunoglu, Mehmet Ali; the Turkish Rotavirus Surveillance NetworkPublication Metadata only Future trends of molecular diagnostics in clinical microbiology(CURRENT BIOLOGY LTD, 2011) KARAHASAN, AYŞEGÜL; Yagci, Aysegul KarahasanPublication Open Access Panton-Valentine leukocidin and biofilm production of Staphylococcus aureus isolated from respiratory tract(J INFECTION DEVELOPING COUNTRIES, 2013-11-15) KARAHASAN, AYŞEGÜL; Aktas, Nilufer Cakir; Erturan, Zayre; Karatuna, Onur; Yagci, Aysegul KarahasanIntroduction: Staphylococcus aureus is one of the first bacteria colonizing in cystic fibrosis (CF) respiratory tract and different virulence factors are responsible for disease progression. It is not clear if CF S. aureus strains are more virulent than strains isolated from non-CF patients. Methodology: Biofilm production was detected by a modified tissue culture plate method, presence of genes encoding for Panton-Valentine leukocidin (PVL) was investigated by a signal amplified sandwich hybridization assay and antimicrobial susceptibility patterns were detected by disk diffusion method. Results: Staphylococcus aureus clinical isolates (n = 88) recovered from respiratory tract specimens in which 31 of them were from cystic fibrosis (CF) patients were analysed. Biofilm production was detected in 96.8% of CF isolates in which 32.3% exhibited strong positive phenotype and in 47.4% of non-CF isolates in which strong positive phenotype was not observed (p < 0.05). All CF isolates were methicillin susceptible, whereas 53.4% of non-CF isolates (n = 31) were methicillin resistant. No resistance was observed for vancomycin, chloramphenicol and trimethoprim/sulfamethoxazole in any of the isolates. PVL genes were detected only in two isolates (2.3%), one from each group, CF and non-CF, which both were methicillin susceptible Conclusion: Biofilm rather than PVL production appears to be an important virulence factor in CF patients.Publication Metadata only Characterization of Staphylococcus aureus Isolates From Cystic Fibrosis Patients(2018-03-22) KARAHASAN, AYŞEGÜL; Özgüler K., Aksu M. B., Eren Fidan E., Karahasan A.ObjectiveStaphylococcus aureus is among the pathogens which colonizes and infects the respiratory tract of cystic fibrosis (CF) patients.This bacterium is the most prevalent pathogen in children and adolescents and replaced or co-existed with Pseudomonas aeruginosa in later periods of the disease.S. aureus produces various virulence factors including exotoxins, enzymes and cell wall proteins facilitating host cell binding (Hotterbeekx A, et al. Front Cell lnfect Microbiol. 2017; 3:106). In this study, we aimed to characterize the antimicrobial susceptibility profile and toxin producing capability of certain S.aureus isolates and cumulative antibiogram results of this pathogen obtained from our CF patients.MethodsTotal of 70 S.aureus isolated from lower respiratory tract samples of CF patients between 2016- October 2017 were included. MALDI-TOF MS (Vitek MS, bioMerieux, France) was used for bacterial identification. An automated system (VITEK 2 Compact, bioMerieux) was used to determine the antimicrobial susceptibility. Five enterotoxins (sea,seb,sec,sed and see), Panton-Valentine leukocidin (PVL;IukS/F) and toxic shock toxin-I (tst) encoding genes were investigated by PCR (Tekeli A, et al. Mikrobiyol Bul. 2009;43:1-10).ResultsAmong the 70 S.aureus isolates, 25 (35.7%) were methicillin-resistant (MRSA). Ali isolates wereresistant to penicillin; resistance rates for erythromycin, ciprofloxacin, levofloxacin, gentamicin,tetracycline, and clindamycin were 42.8%, 17.1%, 7.1%, 14.2%, 27.1%, and 10% respectively. Allisolates were susceptible to vancomycin and tigecycline. Cumulative antibiogram results of S.aureus isolates were shown in Table. PCR analysis for toxin genes revealed 12, 3 and 2 isolates were positive for sea, sec and sed genes, respectively. tst gene was detected in 26 isolates (37.4%), and 21 of the S. aureus isolates (30%) tested positive for the lukS/F genes.Conclusions S. aureus is one of the most common isolated pathogens in CF patients. We found that all the study isolates were resistant to penicillin, but sensitive to various antibiotics. Our results also demonstrated that toxic shock toxin-I and Panton-Valentine leukocidin coding genes were prevalent (37.4% and 30.0%, respectively) in our collection. Antibiotic susceptibility and virulence profiles further emphasise the importance of the characterization of S. aureus isolated in CF.