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    Comparison of Broth Microdilution Method with BD Phoenix, Micro Scan and E-test for Carbapenem-resistant Enterobacterales: Colistin Susceptibility Testing
    (Galenos Publ House, 2022) Yis, Reyhan
    Objective: In the past years, due to the increasing carbapenem resistant Enterobacterales (CRE) infection rates, colistin use has been on the rise. Multi-drug resistant Gram-negative bacteria and colistin resistance are increasing simultaneously; therefore, an accurate method for antimicrobial susceptibility testing of colistin is crucial. Clinical and Laboratory Standards Institute and European Committee on Antimicrobial Susceptibility Testing recommend the standard broth microdilution (BMD) method for colistin minimum inhibitory concentration testing. In this study, we aimed to examine the performance of BD Phoenix, MicroScan, and E-tests on CRE isolates on the determination of colistin susceptibility. The existing commercial tests were compared to the reference BMD method. Methods: One hundred and twenty non-duplicate clinical Enterobacterales isolates such as Klebsiella pneumoniae (K. pneumoniae), Escherichia coli (E. coli), Enterobacter cloace (E. cloacae) were collected between August 2017 to June 2018. The BD Phoenix, MicroScan systems, and E-tests were used to test colistin susceptibility. Commercial methods were compared with the reference method BMD. Results: Colistin susceptibility was evaluated in 120 Gram-negative clinical isolates, including 108 K. pneumoniae, 10 E. coli, 2 E. cloacae, during the study period. Among the isolates, 66 (55%) were susceptible, and 54 (45%) were resistant to colistin, according to BMD. BD Phoenix, MicroScan, and E-test had 90.90%, 95.45%, and 96.96% sensitivity, respectively, when colistin was tested. Conclusion: In routine clinical practice, the worldwide reference method can hardly be implemented, and commercially available systems are used for the interpretation of colistin susceptibility. Colistin use is increasing for the treatment of multiresistant Gram-negative infections, further and more extensive studies are needed for precise susceptibility testing methods for this compound. We recommend that laboratories use the BMD method at least in selected patient groups in the face of increasing antimicrobial resistance.
  • Küçük Resim
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    Comparison of the Efficacy of Colistin and Meropenem Monotherapy with Meropenem/Ertapenem Combination in an Experimental Sepsis Model of Carbapenemase-producing Klebsiella pneumoniae
    (Galenos Publ House, 2022) Yildirim, Deniz Yuce; Ari, Alpay; Yis, Reyhan; Soylu, Fahri Emrah; Tosun, Selma
    Introduction: To investigate the efficacy of double carbapenem therapy (ertapenem + meropenem combination) in an experimental sepsis model in rats with Klebsiella pneumoniae (K. pneumoniae), which is carbapenem-resistant and colistin susceptible, and compare it with colistin and meropenem monotherapy.Materials and Methods: K. pneumoniae isolate that is known to carry the blaOXA-48 and blaNDM carbapenemase genes was used, and 1-2x108 colony forming unit/ml was inoculated intraperitoneally to 40 rats (20 males/20 females), and a sepsis model was created. The rats were divided into four equal groups: control, colistin, meropenem, and meropenem + ertapenem combination. The rats were followed for 24 h for signs of sepsis and mortality. Euthanasia was then performed, and blood cultures were taken.Results: After 24 h, none of the rats in the control or treatment groups died. K. pneumoniae growth was observed in all rats in the control, five in the colistin, seven in the meropenem, and five in the meropenem + ertapenem combination groups. A statistically significant difference was found between the control group and the colistin and meropenem + ertapenem combination groups (p=0.033 and p=0.033, respectively). No statistically significant difference was found between the control group and the meropenem monotherapy group (p=0.215). The numbers of non-growth blood cultures were comparable between the colistin group and the meropenem + ertapenem combination group, and no statistically significant difference was found between the two groups (p=1). The mean time of growth signals (minutes) were compared between the treatment groups: colistin, 642.6 +/- 116.4; meropenem, 582.6 +/- 107.7; and meropenem + ertapenem combination, 701.2 +/- 70.4 min.Conclusion: Meropenem + ertapenem combination treatment was comparable to colistin monotherapy, and the mean time of growth signals of blood cultures were longer than those in the colistin and meropenem monotherapy groups.