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    ANTI-QUORUM SENSING AND ANTITUMOR ACTIVITY OF PRUNELLA VULGARIS, SAMBUCUS NIGRA, CALENDULA OFFICINALIS: potential use in food industry
    (Slovak University of Agriculture, 2021) Tosun, Melike Nur; Demirel Zorba, Nükhet Nilüfer; Yüceer Karagül, Yonca
    With the emergence of health related side effects of synthetic substances, the trend towards natural products has increased and has directed researchers to determine their pharmacological properties. At the same time, the resistance of the microorganisms to the antibiotics used in the treatment revealed that they should be controlled without allowing them to gain resistance. In this study, the total phenolic content, volatile composition and antioxidant, antimicrobial, anti-quorum sensing and antitumor activities of Prunella vulgaris, Sambucus nigra and Calendula officinalis extracts were determined. The antioxidant capacity of the extracts was determined by the Trolox Equivalent Antioxidant Capacity (TEAC) method, volatile component analyses were determined by GC-MS, and antimicrobial activity was determined by the disc diffusion method. Chromobacterium violaceum 026 and Agrobacterium tumefaciens A136 were used to determine the anti-quorum sensing activity. Additionally, the antitumor potential of the extracts was determined by the potato disc method. Prunella vulgaris was the plant with the highest antioxidant capacity, while the extract with the highest antimicrobial activity was determined to be Sambucus nigra against Staphylococcus aureus ATCC 25923. The results showed that all extracts have anti-quorum sensing properties. Prunella vulgaris was the plant with the highest anti-quorum sensing properties. There was a correlation between the extract concentration and tumor inhibition. The Prunella vulgaris extract was found to have the highest antitumor activity. As a result, it was determined that the plants used in the study have the potential to be used in alternative medicine treatment and can be utilized for the control of microorganisms.
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    Disinfection of Clostridioides difficile on spinach with epigallocatechin-based antimicrobial solutions and sodium hypochlorite
    (Elsevier B.V., 2023) Tosun, Melike Nur; Taylan Yalçın, Gizem; Korkmazer, Gizem; Zorba, Murat; Caner, Cengiz; Demirel Zorba, Nükhet Nilüfer
    The removal of C. difficile inoculated on fresh spinach leaves washed with antimicrobial solutions was investigated. In addition, the effect of washing solutions on the total aerobic mesophilic bacteria (TAMB) and Enterobacteriaceae in the fresh spinach was examined. The fresh spinach was washed through immersion in different concentrations (MIC, 2xMIC, and 4xMIC) of the natural disinfectant solution (NDS) consisting of EDTA, borax, and epigallocatechin gallate (EGCG) content developed in our laboratory and green tea extract-acetic acid (GTE-AA) for varying contact times (5 and 15 min). Different concentrations (50, 100, and 200 ppm) of sodium hypochlorite (NaOCl) and tap water as the control group were used to compare the effectiveness of the NDS. In addition, the effects of washing on the color, texture, and total phenol content of the spinach were determined. No statistical difference was observed in the washing of the spinach leaves with NDS prepared at 2xMIC and 4xMIC concentrations, while inhibition of C. difficile ranged between 2.11 and 2.32 logs. The highest inhibition was observed in the application of 50 ppm NaOCl for 15 min with a decrease of 2.88 logs in C. difficile spores. The GTE-AA and NDS decreased the number of TAMB by 2.27–3.08 log and, 3.21–3.66 log, respectively. Washing spinach leaves with natural disinfectant for 5 min caused a decrease of 2.58 logs in Enterobacteriaceae load, while washing with 50 ppm NaOCl for 15 min reduced Enterobacteriaceae load by 4 logs. Tap water was ineffective in reducing any microbial load. No difference was detected in the color parameters of the spinach through all washes. Although all antimicrobial washes made a difference in the texture of the spinach, the greatest loss in firmness was observed in the spinach washed with NaOCl. Washing spinach with epigallocatechin-based wash solutions can remove C. difficile in possible C. difficile contamination, thereby reducing the environmental load of C. difficile. Epigallocatechin-based disinfectants can be an alternative to chlorine-based disinfectants in improving the microbial quality of vegetables.
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    Gıda çalışanlarından izole edilen Enterobacterales suşlarında antimikrobiyal direnç ve GSBL/Karbapenemaz varlığının araştırılması
    (Refik Saydam National Public Health Agency (RSNPHA), 2021) Çakici, Nesrin; Numanoğlu Çevik, Yasemin; Süzük Yıldız, Serap; Akçalı, Alper; Demirel Zorba, Nükhet Nilüfer
    Amaç: Bu çalışma gıda endüstrisi çalışanlarından elde edilen toplum kaynaklı Enterobacterales üyelerinde antimikrobiyal direnç ve Genişlemiş Spektrumlu Beta Laktamaz (GSBL), karbapenemaz üretme durumunun belirlenmesi amacıyla gerçekleştirilmiştir. Yöntem: Çanakkale il merkezi ve ilçelerindeki hastaneler (n: 9) ile gıda işletmelerinde (n: 17) görevli gıda çalışanlarının (n: 300) el sürüntü örnekleri Brain Heart Infusion Broth (BHI) besiyerine alındı. İnokulümler 370 C de 24 saatlik inkübasyondan sonra Eosine Methylen Blue agar (EMB) besiyerine ekildi. Bakterilerin tanımlanmasında klasik identifikasyon ve Matriks aracılı lazer desorpsiyon iyonizasyon uçuş süresi kütle spektrometrisi (MALDITOF MS) yöntemi kullanıldı. Sefotaksim, seftazidim, meropenem ve ertapenem antibiyotiklerine karşı direnci ölçmek için disk difüzyon ve minimal inhibitör konsantrasyon (MİK) yöntemleri uygulandı ve EUCAST 2020’ye göre değerlendirildi. Tarama testi sonuçlarına göre GSBL ve karbapenemaz fenotipik doğrulama testleri uygulandı. GSBL pozitif bulunan izolatlarda polimeraz zincir reaksiyonu (PZR) yöntemine göre CTX-M geni araştırıldı. Bulgular: Elde edilen 222 adet gram negatif bakterinin tür bazında dağılımı; 129 (%58.1) Klebsiella pneumoniae, 32 (%14.4) Enterobacter cloacae, 31 (%13.9) Acinetobacter baumannii, 11 (%4.9) Escherichia coli, 8 (%3.6) Enterobacter asburiae, 4 (%1.8) Escherichia hermanni, 3 (%1.4) Enterobacter aerogenes 2 (%0.9) Klebsiella oxytoca, 2 (%0.9) Enterobacter cancerogenus olarak belirlendi. Enterobacterales üyelerinden (n: 191) 7 (%3.7)’sinin klinik sınır değerlere göre sefotaksime dirençli (<17 mm) olduğu tespit edildi. Sefotaksim inhibisyon çapı GSBL tarama sınır değeri altında (<21 mm) tespit edilen 13 izolatın kombine disk ve çift disk sinerji testi sonuçlarına göre 2 adet bakterinin (K. pneumoniae, E. cloacae) GSBL pozitif olduğu belirlendi. PZR yöntemine göre K. pneumoniae izolatının CTX-M geni taşıdığı ve hastanede görevli olan bir gıda çalışanından izole edildiği tespit edildi. Enterobacterales suşlarının ve A. baumannii izolatlarının hiçbirinde karbapenem direncine rastlanmadı. Meropenem inhibisyon zon çapı 28 mm’den küçük olan 46 adet Enterobacterales türünün meropenem MİK değeri 8 mg/l ile 0.125 mg/l arasında bulunmuştur. Meropenem zon çapı karbapenemaz tarama sınır değerinin (<25 mm) altında tespit edilen 2 adet izolata kombinasyon disk testi uygulandı buna göre karbapenemaz negatif olduğu tespit edildi. Sonuç: Toplumda dirençli bakteri el taşıyıcılığının düşük olması (%3.7), toplum kaynaklı izolatların GSBL pozitifliğinin oldukça düşük (%1.04) bulunması, karbapenemaz pozitifliğine rastlanmaması antibiyotik dirençli izolatların gıda çalışanlarında düşük olduğunu düşündürmektedir. Gıda çalışanlarında bu sayıda gram negatif bakterilerin tespit edilmesi hijyen eğitimlerine önem verilmesi gerektiğini düşündürmüştür.
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    In-vitro determination of inhibitory effects of probiotic strains on Clostridioides difficile
    (Academic Press, 2023) Yalçın, Gizem Taylan; Tosun, Melike Nur; Demirel Zorba, Nükhet Nilüfer
    Commercial probiotic strains inhibited C. difficile, and other Clostridium cultures with zones 14.2–78.9 mm. The highest inhibition was observed with commercial culture on C. difficile ATCC 700057. Organic acids were the leading cause of inhibition. Probiotic cultures may be used as a support culture or through fermented foods for treatment.
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    Presence of Clostridioides difficile on spinach, carrots, cheese and milk in Turkey
    (Elsevier Sci Ltd, 2025) Taylan Yalçın, Gizem; Tosun Demir, Melike Nur; Korkmazer, Gizem; Akçalı, Alper; Demirel Zorba, Nükhet Nilüfer
    Introduction: The presence of Clostridioides difficile in water, soil, fertilizers, and animal feces suggests the potential existence of C. difficile in foods that come into contact with these sources or become contaminated through indirect means. Material & method: A total of 431 samples, consisting of spinach and carrots and raw milk and cheese obtained from cows, goats, buffalo, and sheep, were examined for the presence of C. difficile. Isolates were identified by real-time PCR, ribotyped, and their toxin profiles were determined. Antibiotic susceptibility to vancomycin, clindamycin, and metronidazole was evaluated using the E-test. Results: C. difficile was detected in 3.27 % (4/122) of spinach, 1.85 % (2/108) of carrots, and 2.19 % (2/91) of milk samples. No C. difficile was detected in the cheeses (n = 110). All isolates were obtained from different fields/farms. Only one isolate (from spinach) carried the tcdA and tcdB toxin genes. Six different PCR ribotypes were detected, with two (001, 060) being identified. All isolates were sensitive to vancomycin, clindamycin, and metronidazole. Conclusion: The prevalence of C. difficile in spinach, carrot, and milk samples from selected regions was low, and nontoxigenic strains were prevalent. Despite the low prevalence, the detection of C. difficile in these foods highlights the potential risk of foodborne transmission of this pathogen and underscores the need for monitoring and control strategies to ensure food safety.