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Author: search.filters.author.Sancak, BanuSubject: search.filters.subject.Escherichia coli

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    Evaluation of a Commercial Broth Microdilution Panel for Colistin Susceptibility Testing of Clinical Isolates of Escherichia coli and Klebsiella pneumoniae
    (2021) Mirza, Hasan C.; Bicakcigil, Asiye; Liste, Umran; Sancak, Banu; 0000-0002-8853-3893; 33978373; F-1232-2015
    Background: Colistin is among the last resort antibiotics for the treatment of infections caused by multidrug-resistant Gram-negative pathogens. Antimicrobial susceptibility testing of colistin is challenging due to its physicochemical properties. Broth microdilution (BMD) is the recommended method for colistin susceptibility testing. However BMD is not practical for clinical microbiology laboratories as manual preparation of BMD plates is time-consuming and labor intensive. Recently, some more user-friendly BMD products with commercial panels have become available. Our objective was to evaluate the performance of a commercial broth microdilution (BMD) product [Sensititre (Thermo Fisher Scientific)] for colistin MIC determination by comparison with reference BMD method using a collection of E. coli and K. pneumoniae isolates. Methods: A total of 323 unique patient isolates (102 E. coli, 221 K. pneumoniae) were included in the study. Isolates were stored at -70 degrees C and subcultured twice on sheep blood agar before testing. Colistin MICs of the isolates were determined using Sensititre (a premade BMD product with dried antibiotics) and an 'in-house prepared BMD panel prepared in accordance with CLSI guidelines' (reference method). MIC determination with Sensititre was performed according to manufacturer's instructions. The reference method was performed using untreated 96-well sterile polystyrene plates. Colistin MIC results were interpreted according to EUCAST breakpoints (susceptible, <= 2 mg/L; resistant, > 2 mg/L). Results: Overall susceptibility rate of isolates to colistin by reference BMD was 75.9%. Overall categorical agreement (CA), essential agreement (EA), very major error (VME), and major error (ME) rates for Sensititre were 98.5%, 72.5%, 3.8%, and 0.8%, respectively. The CA and EA between Sensititre and reference BMD for the isolates with reference colistin MICs close to the susceptibility breakpoint (2 - 8 mg/L) was 94.2% and 48.1%, respectively. Sensititre yielded a VME rate of 15% and ME rate of 0%, respectively, for this subset of isolates. Conclusions: In conclusion, Sensititre showed high CA but low EA with reference BMD for entire collection of isolates. The VME rate was just slightly above 3% and ME rate was acceptable. The rates of CA and EA were decreased and the rate of VME was increased when a subset consisting of more challenging isolates was used.
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    Comparison of Antimicrobial Susceptibilities of Escherichia coli Isolated From Urinary Cultures of Different Patient Groups: A University Hospital Experience
    (2020) Mirza, Hasan Cenk; Sancak, Banu; F-1232-2015
    Objective: Our objective was to investigate the antimicrobial susceptibilities of Escherichia coli isolated from urinary cultures in Central Laboratory of Hacettepe University Faculty of Medicine Hospital and to examine the differences between antimicrobial susceptibilities of E. coli isolated from different patient groups. Methods: E. coli isolated from urinary cultures between January 1, 2017 and April 30, 2018 were included in our study. Automated systems, i.e. VITEK (R) 2 Compact (bioMerieux, Marcy l'Etoile, France) and BD Phoenix (Becton Dickinson, Sparks, MD, USA) and disk diffusion test were used for the determination of antimicrobial susceptibilities. The patients from whom the bacteria were isolated were divided into groups according to age (<18 years, 18-64 years, and >64 years), gender and patient care (outpatients/inpatients). Results: The highest susceptibility rates were observed for carbapenems (>99%), fosfomycin (98.5%), nitrofurantoin (98.3%) and amikacin (94.2%), whereas the highest resistance rates were observed for ampicillin (61.3%) and amoxicillin-clavulanate (37.5-45.7%). Antimicrobial resistance rates of isolates from patients aged 65 years and over were higher than those of patients in other age groups, with the exception of piperacillintazobactam, amikacin and ertapenem. The resistance rates of isolates belonging to male patients were higher than those belonging to female patients for all antimicrobials. Also, the resistance rates of isolates belonging to inpatients were higher than those belonging to outpatients for all antimicrobials. When the rates of extended-spectrum beta-lactamase (ESBL)-producing E. coli from different age groups were compared, the highest rate (34.2%) was observed among the isolates from patients aged 65 years and over. The rates of ESBL-producing E. coli from males (33.9%) and inpatients (36.3%) were higher than those from females (23.8%) and outpatients (23.3%), respectively. Conclusions: Antimicrobial susceptibilities of E. coli isolates may vary among different patient groups. Demographic features of patients may guide for selecting the antimicrobials for empiric treatment of urinary tract infections.