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    Investigation of EDTA-CarbaNP-direct test for the detection of metallo-β-lactamases in Pseudomonas aeruginosa
    (Elsevier Science Inc, 2025) Tutan, Hanife; Mazlumoglu, Bilge; Cizmeci, Zeynep; Cekin, Zuhal Kalayci; Comert, Fusun; Tanriverdi, Elif Seren; Aktas, Elif
    Background: WHO has included carbapenem-resistant Pseudomonas aeruginosa (CR-Pa) in the high priority pathogens list. Ceftazidime-avibactam (CZA) is one of the limited treatment options in CR-Pa infections. Early detection of metallo-beta-lactamases (MBL) is important because CZA is not effective against MBL-producing isolates. Aim: To modify the CarbaNP-direct test (CNPdt) with EDTA and evaluate its use in MBL detection and prediction of CZA resistance CR-Pa isolates. Methods: 398 CR-Pa isolates from five centres in T & uuml;rkiye were included. Susceptibility tests were done using EUCAST criteria. The isolates were tested for blaVIM, blaIMP, blaNDM, blaOXA-48, blaKPC and blaGES genes using Biospeedy Carbapenem-Resistance qPCR kit and GES Antibiotic-Resistance kit (Bioeksen, T & uuml;rkiye). We modified CNPdt described by Pasteran et al. by adding a third tube with ethylenediaminetetraacetic acid (EDTA). The isolates with carbapenemase genes were subjected to CNPdt and EDTA-CNPdt. EDTA-CNPdt was considered positive if the tube without EDTA turned yellow while the tube with EDTA remained red and negative if both tubes turned yellow (Fig. 1). Results: Carbapenemase genes were detected in 55 (13.8 %) of the isolates. CNPdt was positive in 31 of the isolates. Of the 31 isolates, 23 were positive for EDTA-CNPdt. All of these 23 isolates were MBL producers and resistant to CZA. PCR, CNPdt, EDTA-CNPdt and CZA susceptibility test results are shown in Table 2. Conclusion: The positivity of CNPdt in CR-Pa is limited, but EDTA-CNPdt detected 100 % of MBL-producing isolates when CNPdt was positive. This test can be used for MBL detection and prediction of CZA resistance in CNPdt positive isolates.
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    Investigation of High-Risk ST131 Clone in ESBL-Producing Escherichia coli Isolates Isolated from Urine and Non-urinary Clinical Specimens with MALDI-TOF MS and Real Time PCR
    (Ankara Microbiology Soc, 2018) Cizmeci, Zeynep; Otlu, Baris; Aktas, Elif; Ordekci, Seyhan; Acikgoz, Ozlem; Gulec, Nuray
    In recent years, the ST131 clone was identified as a high risk pandemic clone among Escherichia coli isolates by multilocus sequence typing (MLST) studies and has been associated with extended spectrum beta-lactamase (ESBL) production (often with CTX-M-15) and antibiotic resistance especially against fluoroquinolones. The aim of this study was to determine the rate of high risk ST131 clone in ESBL producing E.coli isolates in our region, to investigate the sensitivity of MALDI-TOF MS in the detection of ST1 31 clone, and to compare the frequency of antimicrobial resistance among ST131 and non-ST1 31 isolates. A total of 251 urinary and 50 non-urinary E.coli isolates identified in our hospital central laboratory between February 2016-February 2017 were included in the study. Real-time PCR and MALDI-TOF MS methods were used for the detection of E.coli ST131 clone. For the statistical evaluation of the rate of antibiotic resistance among isolates of ST131 and non-ST131 clones, chi-square test was used. p value under 0.05 was considered as significant. Of the 301 isolates, 110 (36.6%) and 92 (30.6%) isolates were identified as ST131 clone by real-time PCR and MALDI-TOF MS, respectively. According to real-time PCR results, 91 (36.3%) of 251 urinary isolates and 19 (38%) of 50 non-urinary isolates were found as ST1 31 clone; there was no statistically significant difference between the groups. Ciprofloxacin resistance was found to be significantly higher in ST131 isolates than the non-ST131 isolates (78.2%, n= 86 vs. 53.4%, n= 102). No statistically significant difference was determined for the other antibiotics tested. For the detection of E.coli ST131 clone; sensitivity of MALDI-TOF MS was 84%, specificity was 100% while positive predictive value was 100% and negative predictive value was 92%. In conclusion, further investigation of the high risk E.coli ST1 31 clone in our country, in which ESBL ratios and antibiotic resistance rates, especially in fluoroquinolones, are high, is important for the development of new strategies to control antibiotic resistance. MALDI-TOF MS method is particularly useful for easy and fast detection of the high risk E.coli ST131 clone.
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    Molecular characterization of carbapenem-resistant Enterobacteriaceae yields increasing rates of NDM-1 carbapenemases and colistin resistance in an OXA-48-endemic area
    (Taylor & Francis Ltd, 2017) Cizmeci, Zeynep; Aktas, Elif; Otlu, Baris; Acikgoz, Ozlem; Ordekci, Seyhan
    We aimed to characterize carbapenem-resistant isolates in a tertiary hospital in Istanbul, Turkey, high-prevelance area for OXA-48 producers. About 76 Enterobacteriaceae clinical isolates were included. Carbapenemase production was detected by Carbapenem Inactivation Method and carbapenemase genes were investigated by PCR. The clonal relationships were evaluated by AP-PCR. Nineteen Klebsiella pneumoniae isolates were colistin resistant. About 75 isolates yielded carbapenemase by CIM. 52 OXA-48, 17 NDM-1 and 2 VIM-5 carbapenemase genes were detected. Co-production of 'OXA-48 and NDM-1' and 'OXA-48 and VIM-5' were demonstrated in two Klebsiella pneumoniae isolates. The total clustering rate was 20.2%. About 69 Klebsiella pneumoniae yielded 60 profiles and 12 isolates formed five clusters. We have demonstrated the presence of OXA-48 carbapenemases in the majority of isolates in a large collection of carbapenemase-producing isolates from a single hospital. The relatively high rates of NDM-1-producing isolates and colistin resistance is noteworthy.