Evaluation of Teicoplanin Resistance Detected by Automated System in Coagulase Negative Staphylococci: A Comparison with
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Evaluation of Teicoplanin Resistance Detected by Automated System in Coagulase Negative Staphylococci: A Comparison with Gradient Test and Broth Microdilution Methods Ayşe Barış1,2 · Gülşah Malkoçoğlu3 · Ecem Büyükyanbolu1 · Feride Merve Aslan1 · Banu Bayraktar1 · Elif Aktaş1 Received: 24 February 2020 / Accepted: 22 July 2020 © Springer Science+Business Media, LLC, part of Springer Nature 2020
Abstract Upon the observation of an increase in teicoplanin resistance rates in coagulase negative staphylococci (CoNS) isolates determined by the automated system, we aimed to compare the automated system and gradient test methods with the gold standard broth microdilution method. In addition, the effect of standard antimicrobial susceptibility guidelines on teicoplanin susceptibility test results in CoNS was investigated. A total of 81 CoNS isolates, 52 resistant and 29 susceptible to teicoplanin determined by automated system (Phoenix, Becton Dickinson, USA), were tested. The minimum inhibitory concentration (MIC) values were determined by gradient test (M.I.C. Evaluators, OXOID, UK) and broth microdilution methods. Susceptibility categories were determined according to EUCAST and CLSI criteria and the results were compared. Among 29 isolates found to be susceptible by automated system, one isolate was found resistant by gradient and broth microdilution tests. Of the 52 resistant isolates determined by automated system, 12 (23%) were found to be resistant by gradient test and 22 (42.3%) were resistant by broth microdilution. According to CLSI criteria, no resistant isolates were detected by broth microdilution and six isolates were intermediately susceptible while, two isolates were detected to be resistant and five isolates were found to be intermediately susceptible by the gradient test. In conclusion, compared to microdilution, teicoplanin resistance was detected at a higher rate in CoNS isolates by the automated system used. On the other hand, the gradient test method which is frequently used for confirmation was not reliable in MIC values close to the EUCAST breakpoint values (4 μg/mL). In addition, lower resistance rates were observed when the CLSI breakpoints were used in gradient test and broth microdilution methods.
Introduction
This manuscript was presented in International XXXVIII. Turkish Microbiology Congress, 4–8 November 2018, Antalya, Turkey. * Ayşe Barış [email protected] Gülşah Malkoçoğlu [email protected] 1
Department of Medical Microbiology, University of Health Sciences, Sisli Hamidiye Etfal Research and Training Hospital, Halaskargazi, Etfal Street, 34371 Sisli/İstanbul, Turkey
2
Department of Medical Microbiology, Istanbul Medical Faculty, Istanbul University, Istanbul, Turkey
3
Kocaeli Public Health Laboratory, Kocaeli, Turkey
Coagulase Negative Staphylococci (CoNS) are important members of normal skin flora in humans. With the increased use of prosthetics and invasive techniques in medicine, CoNS cause extremely serious, difficult to treat infections w
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