Zerrin Aktas - Academia.edu (original) (raw)

Papers by Zerrin Aktas

Flora the Journal of Infectious Diseases and Clinical Microbiology, 2021

İnsan mikrobiyotası, konakçının belirli yüzeylerinde (barsak, deri, ağız vb.) konumlanmıştır ve 1... more İnsan mikrobiyotası, konakçının belirli yüzeylerinde (barsak, deri, ağız vb.) konumlanmıştır ve 10 13 ile 10 14 kadar mikroorganizmaya ev sahipliği yapmaktadır. Bağırsak mikrobiyotası ürettikleri SCFA ("Short-Chain Fatty Acid"= SCFA)'lar ile insan fizyolojisinde, bağırsak mukozal bariyerinin yapısal bütünlüğünü koruyarak patojenlerin kolonizasyonunu engellemek, barsak-beyin ekseni iletişimine katılmak, bağışıklık sistemini hazırlamak ve besin sindirimine katkıda bulunmak gibi rollere sahiptir. Bağırsak mikrobiyotasının immün sistemle olan yakın ilişkisinin yanı sıra genetik faktörlerle de ilişkisi bulunur. MUC2, MyD88, IgA, NOD2, NLRP6 ve TLR5 gibi konakçı genlerdeki mutasyonlar, bağırsak mikrobiyal kompozisyonu üzerinde önemli bir etkiye sahiptir ve bağırsak homeostazını veya disbiyozisi belirleyebilir. Konakçının bağışıklık sistemi bir ekosistem yöneticisi gibi çalışır ve mikrobiyal bileşimin çeşitliliğini kontrol etmede kritik bir rol oynar. MHC (Major Histocompatibility Complex) genleri de dahil olmak üzere konağın immün sistemi ile ilgili genetik faktörler, bağırsak mikrobiyal kompozisyonu üzerinde güçlü bir etkiye sahiptir.

Mucilage Problem in the Sea of Marmara, Mar 23, 2023

Marmara Denizi'nin Müsilaj Sorunu, Feb 2, 2023

Journal of Biomaterials Science, Polymer Edition

Coatings

The study was based on understanding the relationship between titanium (Ti) doping amount and mag... more The study was based on understanding the relationship between titanium (Ti) doping amount and magnetic heating performance of magnetite (Fe3O4). Superparamagnetic nanosized Ti-doped magnetite ((Fe1−x,Tix)3O4; x = 0.02, 0.03 and 0.05) particles were synthesized by sol-gel technique. In addition to (Fe1−x,Tix)3O4 nanoparticles, SiO2 coated (Fe1−x,Tix)3O4 nanoparticles were produced as core-shell structures to understand the effects of silica coating on the magnetic properties of nanoparticles. Moreover, the magnetic properties were associated with the Néel relaxation mechanism due to the magnetic heating ability of single-domain state nanoparticles. In terms of results, it was observed that the induced RF magnetic field for SiO2 coated (Fe0.97,Ti0.03)3O4 nanoparticles caused an increase in temperature difference (ΔT), which reached up to 22 °C in 10 min. The ΔT values of SiO2 coated (Fe0.97,Ti0.03)3O4 nanoparticles were very close to the values of uncoated Fe3O4 nanoparticles.

The study is based on understand the titanium (Ti) doping effect to enhance the Neel relaxation a... more The study is based on understand the titanium (Ti) doping effect to enhance the Neel relaxation at magnetic heating performance of magnetite (Fe3O4). Ti doped magnetite ((Fe1-x,Tix)3O4; x= 0.02, 0.03 and 0.05) superparamagnetic nanoparticles were synthesized via sol-gel technique. The analyses were performed for (Fe1-x,Tix)3O4 and core-shell (SiO2 coated (Fe1-x,Tix)3O4) nanoparticles in order to understand the influence of silica coating on the magnetic properties of nanoparticles. The target of study to enhance the Neel relaxation mechanism on magnetic heating. The interparticle spacing and Ti amount were two parameters that we focused on the study. The results provided that coating with SiO2 has no specific effect on heating performance of (Fe1-x,Tix)3O4 nanoparticles. While the increase in temperature (ΔT) under 150 kHz RF signal reached up to 22oC in 10 minutes for SiO2 coated (Fe0.97,Ti0.03)3O4 nanoparticles, which was very close value of uncoated Fe3O4 nanoparticles.

Journal of Istanbul Faculty of Medicine / İstanbul Tıp Fakültesi Dergisi

Objective: In our study, we analyzed gut microbiota in allo-HSCT patients and aimed to evaluate t... more Objective: In our study, we analyzed gut microbiota in allo-HSCT patients and aimed to evaluate the relationship of gut microbiota with transplant complications, mainly GVHD. Materials and Methods: A total of 25 adult recipients and donors who underwent allo-HSCT at Istanbul Anadolu Medical Center were included in the study. Stool samples were collected twice, before chemotherapy regimen and after allo-HSCT. Samples were analyzed by High Melting (HRM) Analysis and Next Generation Sequencing (NGS) methods after nucleic acid isolation. Sequencing was done with Illumina MiSeq. Bacteria Silva database was used for taxonomic classification and QIIME 2 programs were used for analysis. Statistical analyses were carried out with the R statistical programming language. Gut microbiota affect in allogeneic stem cell transplant patients

Sağlık Bilimlerinde İleri Araştırmalar Dergisi / Journal of Advanced Research in Health Sciences

Bu çalışmada, çeşitli klinik örneklerden izole edilen karbapenemlere dirençli Klebsiella pneumoni... more Bu çalışmada, çeşitli klinik örneklerden izole edilen karbapenemlere dirençli Klebsiella pneumoniae izolatlarında bla OXA-48 benzeri , bla CTX-M-15 , bla NDM-1 genlerinin varlığı ve apramisine duyarlılıklarının araştırılması amaçlanmıştır. Gereç ve Yöntem: Çalışmaya Haziran-Eylül 2020 tarihleri arasında İstanbul Tıp Fakültesi Hastanesinde yatan hastalara ait çeşitli klinik örneklerden izole edilen 12 çoğul dirençli K. pneumoniae izolatı dahil edilmiştir. Bu izolatlarda imipenem, meroperem, ertapenem ve apramisin için minimum inhbisyon konsantrasyon (MİK) değerleri, EUCAST önerilerine göre sıvı mikrodilüsyon yöntemiyle saptanmıştır. Antibiyotik konsantrasyonları EUCAST (imipenem, meropenem, ertapenem) ve NARMS (apramisin) klinik sınır değerlerini kapsayacak şekilde <0,016-256 µg/mL olarak belirlenmiştir. Klasik polimeraz zincir reaksiyonu (PCR) yöntemiyle K. pneumoniae izolatlarında bla OXA-48, bla NDM-1 , bla CTX-M-15 genlerinin varlığı araştırılmıştır. Bulgular: Karpanenemlere dirençli K. pneumoniae izolatlarının tamamında (n=12) bla OXA-48 benzeri ve bla CTX-M-15 genleri, bir izolatta (%8,33) bla NDM-1 geni saptanmıştır. İzolatlarının tümü ertapeneme, %91,7'si meropeneme ve %58,3'ü imipeneme dirençli bulunmuştur. Tüm izolatların apramisine duyarlı olduğu belirlenmiştir. MİK aralığı ertapenem için 4-256 µg/mL, meropenem için 0,5-64 µg/mL, imipenem için 0,5-128 µg/mL, apramisin için <0,016-2 µg/mL aralığında saptanmıştır. Sonuç: K. pneumoniae izolatlarında apramisin için düşük MİK değerlerinin saptanması, karbapenemlere veya tüm antibiyotiklere dirençli izolatlarda, tedavide alternatif olarak kullanılabilecek bir ajan olabileceğini düşündürmektedir. Bu nedenle apramisinin klinikte kullanılabilmesiyle ilgili daha kapsamlı çalışmalara ihtiyaç duyulmaktadır.

DergiPark (Istanbul University), Jul 10, 2020

Bu çalışmada, kan kültürlerinden izole edilen bakterilerin kümülatif antimikrobiyal verileri araş... more Bu çalışmada, kan kültürlerinden izole edilen bakterilerin kümülatif antimikrobiyal verileri araştırılmış ve klinisyenlerin ampirik tedavi seçimine katkıda bulunulması amaçlanmıştır. Gereç ve Yöntem: Çalışmaya Ocak 2018-Mayıs2019 arasında çalışılan kan kültürleri dahil edilmiştir. Sadece izolat sayısı >30 olan bakteriler değerlendirilmiştir. Her hasta için ilk izolat çalışmaya dahil edilmiştir. Ampirik tedavi için kümülatif antibiyotik duyarlılık sınırı >%90 olarak kabul edilmiştir. Bulgular: Metisiline dirençli Staphylococcus aureus izolatlarında ampirik tedavi için en uygun antibiyotiklerin vankomisin, teikoplanin ve linezolid olduğu; metisiline duyarlı S. aureus izolatlarında bu antibiyotiklere ek olarak kotrimoksazol ve tetrasiklin seçeneklerinin olduğu bulunmuştur. Enterococcus faecalis izolatlarında vankomisin, teikoplanin ve linezolide ek olarak ampisilin ve yüksek düzey gentamisinin ampirik tedaviye uygun olduğu bulunurken, Enterococcus faecium izolatlarında tek ampirik tedavi seçeneğinin linezolid olduğu belirlenmiştir. Genişlemiş spektrumlu beta laktamaz oluşturmayan grupta karbapenemlere ek olarak 3. ve 4. kuşak sefalosporinler, aminoglikozidler ve piperasilin+tazobaktam ampirik tedavi için uygun olmasına rağmen, GSBL oluşturan Escherichia coli izolatlarında sadece karbapenem grubu antibiyotikler ampirik tedavi için uygun bulunmuştur. GSBL pozitif Klebsiella pneumoniae için ampirik tedavi seçeneği olmadığı ve bu grupta karbapenem direncinin % 50'ye ulaştığı bulunmuştur. GSBL negatif izolatlarda 3. ve 4. kuşak sefalosporinler, karbapenemler, aminoglikozidler ve siprofloksasinin ampirik tedavi için uygun olduğu bulunmuştur. Sonuç: Çalışmamızda elde edilen yüksek direnç oranları nedeniyle, düzenli sürveyans takibinin yapılması gerekmektedir. Karbapenemleri de kapsayan çoğul dirençli mikroorganizmalar için antibiyotik kombinasyonlarının etkinliğini test eden çalışmalara ihtiyaç vardır.

Journal of Materials Science

Acta Microbiologica et Immunologica Hungarica

Treatment of infections caused by OXA-48 carbapenemase producing multidrug-resistant isolates oft... more Treatment of infections caused by OXA-48 carbapenemase producing multidrug-resistant isolates often necessitates combination therapy. In vitro effect of different antibiotic combinations against multidrug-resistant (MDR) Klebsiella pneumoniae isolates were evaluated in this study. Meropenem-tobramycin (MER+TOB), meropenem-ciprofloxacin (MER+CIP), colistin-meropenem (COL+MER), colistin-ciprofloxacin (COL+CIP) and colistin-tobramycin (COL+TOB) combinations were tested by time kill-assays. Each antibiotic alone and in combination at their Cmax values were tested against 4 clinical K. pneumoniae isolates at 1, 2, 4, 6, 8, 12 and 24 h. Effect of colistin and its associations were also assessed at 30 min. Bactericidal activity was defined as ≥3log10 CFU mL−1 decrease compared with initial inoculum. Synergy was defined as ≥2log10CFU mL−1 decrease by the combination compared with the most active single agent. Presence of bla OXA-48, bla NDM, bla VIM, bla IMP, bla KPC and bla CTX-M-1 genes w...

Journal of Antimicrobial Chemotherapy

Background Antimicrobial resistance (AMR) is one of the biggest threats to global public health. ... more Background Antimicrobial resistance (AMR) is one of the biggest threats to global public health. Selection of resistant bacteria is driven by inappropriate use of antibiotics, amongst other factors. COVID-19 may have exacerbated AMR due to unnecessary antibiotic prescribing. Country-level knowledge is needed to understand options for action. Objectives To review AMR in Türkiye and initiatives addressing it. Identifying any areas where more information is required will provide a call to action to minimize any further rise in AMR within Türkiye and to improve patient outcomes. Methods National AMR initiatives, antibiotic use and prescribing, and availability of susceptibility data, particularly for the key community-acquired respiratory tract infection (CA-RTI) pathogens Streptococcus pneumoniae and Haemophilus influenzae, were identified. National and international antibiotic prescribing guidelines commonly used locally for specific CA-RTIs (community-acquired pneumonia, acute otitis...

Future Microbiology

Background: The authors aimed to determine the efficacy of frequently used antibiotics, alone or ... more Background: The authors aimed to determine the efficacy of frequently used antibiotics, alone or in combination, against biofilms of ventilator-associated pneumonia isolates. Materials & methods: The authors determined the MICs, minimum biofilm inhibitory concentrations and minimum biofilm eradication concentrations of meropenem, ciprofloxacin and colistin as well as their combinations against planktonic forms and biofilms of Pseudomonas aeruginosa, Klebsiella pneumoniae and Acinetobacter baumannii clinical isolates. Results: Generally, the minimum biofilm inhibitory concentrations and minimum biofilm eradication concentrations of the antibiotics were 1000-fold higher than their MICs, and synergy was provided by different concentrations of meropenem-colistin and meropenem-ciprofloxacin combinations with checkerboard and time–kill curve methods. Conclusion: The combination of meropenem and ciprofloxacin seems to be a good candidate for the treatment of biofilm-associated infections; ...

Clinical laboratory, 2021

BACKGROUND Early and accurate detection of carbapenemase-producing Enterobacterales (CPE) is fund... more BACKGROUND Early and accurate detection of carbapenemase-producing Enterobacterales (CPE) is fundamental to prevent their spread in hospital environment. Our objective was to compare between four commonly used phenotypic assays and Check-Direct CPE (CDCPE) multiplex PCR in CPE detection. We examined stool samples or rectal swabs for CPE, samples collected from 23 Jan 2017 to 23 Jul 2017 from patients in intensive-care units (ICUs) of our hospital. METHODS A panel of 98 non-repetitive Enterobacterales isolates with reduced susceptibility to carbapenems were analyzed by means of (i) Modified Hodge Test (MHT), (ii) Blue Carba test (BCT), (iii) Combined Disc Test (CDT), and (iv) The Carbapenem Inactivation Method (CIM). All these phenotypic tests compared with CDCPE. Confirmation and validation of results was achieved by classical PCR and sequencing. RESULTS Of the 98 non-repetitive Enterobacterales isolates, ninety-one were K. pneumoniae (93%), three K. oxytoca (3%), three E. cloacae (...

The CTX-M-1 group was found in 86.8% of the Escherichia coli isolates from Istanbul. A subset stu... more The CTX-M-1 group was found in 86.8% of the Escherichia coli isolates from Istanbul. A subset study revealed all isolates carrying bla CTX-M-15 genes flanked by the insertion element ISEcp1. Plasmid typing of transconjugates carrying bla CTX-M-15 showed that most isolates belonged to the Inc/rep FII group but that one isolate also belonged to the FI group.

Antimicrobial Resistance & Infection Control, 2020

Background Treatment of pandrug-resistant isolates often necessitates combination therapy. Checke... more Background Treatment of pandrug-resistant isolates often necessitates combination therapy. Checkerboard synergy and time-killing assay tests were performed to evaluate the benefits of a triple combination with meropenem, ertapenem, and colistin against 10 colistin-resistant K. pneumoniae clinical isolates harboring different β-lactamases. (blaOXA-48, blaNDM). Materials and methods In this study, ertapenem and meropenem (ERT/MEM), meropenem and colistin (MEM/COL), ertapenem, meropenem and colistin (ERT/MEM/COL) combinations were tested using checkerboard techniques and time-kill assays of each antibiotic alone and in combination against 10 colistin-resistant clinical K. pneumoniae isolates. An analysis of K. pneumoniae isolate B6 using a scanning electron microscope revealed morphologic changes in the cell surface after treatment with each antibiotic both alone and in combination. The whole genome of K. pneumoniae KPNB1 was sequenced using an Ion Torrent PGM sequencer. Results Accord...

Journal of Clinical Laboratory Analysis, 2020

The aim of this study was to provide information about the spread and characteristics of the vanc... more The aim of this study was to provide information about the spread and characteristics of the vancomycin‐resistant Enterococcus faecium isolates (VREfm) in Turkey.

Microbial Drug Resistance, 2018

Background: Fifty isolates of Klebsiella pneumoniae isolated from clinical samples between 2012 a... more Background: Fifty isolates of Klebsiella pneumoniae isolated from clinical samples between 2012 and 2016 that were found to be resistant to carbapenems were included in this study. Materials and Methods: Resistance genes were investigated by performing PCR. Plasmid typing was performed using PCR-based replicon typing. The clonal relationships between the strains were investigated using pulsed-field gel electrophoresis (PFGE). Results: OXA-48-type carbapenemase genes were detected in 86% (n = 43/50) of K. pneumoniae isolates, whereas NDM-type carbapenemase genes were detected in 14% (n = 7/50) of the isolates. blaTEM was detected 60% (n = 30) of the strains, blaSHV in 78% (n = 39), blaCTX-M-1 in 48% (n = 24), and blaCTX-M-2-type β-lactamase in 10% (n = 5). blaCTX-M-1 and blaSHV were concomitantly distributed in 40% (n = 20) of the strains, blaTEM and blaSHV in 54% (n = 27), blaTEM, blaSHV, and blaCTX-M-1 in 32% (n = 16) and blaCTX-M-1 and blaCTX-M-2 in 10% (n = 5). Strain numbers 66, 69, 76, 77, and 78 coproduced carbapenemases, blaCTX-M-1 and blaCTX-M-2 in addition to blaOXA-48 or blaNDM-1 that were described as hybrid strains. IncR-type replicon was found in 50% (n = 25) of 50 isolates with plasmid typing, whereas IncA/C-type replicon was detected in 40% (n = 20) and IncFIIK-type replicon in 18% (n = 9) of the isolates. Outcomes of the transformation experiments showed that the OXA-48 gene was carried to the receiver cell on FII plasmids. No dominant epidemic clone was detected through PFGE. Conclusion: OXA-48 carbapenemase was found to be the most prevalent type of enzyme in our hospital, and the presence of NDM-1-type carbapenemase-carrying strain and an increase in their rate were detected.