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Determination of Colistin Resistance by Simple Disk Diffusion Test Using Modified Mueller-Hinton Agar

Authors
 Jean Damascene Uwizeyimana  ;  Daewon Kim  ;  Hyunsook Lee  ;  Jung-Hyun Byun  ;  Dongeun Yong 
Citation
 ANNALS OF LABORATORY MEDICINE, Vol.40(4) : 306-311, 2020-07 
Journal Title
ANNALS OF LABORATORY MEDICINE
ISSN
 2234-3806 
Issue Date
2020-07
Keywords
Colistin ; Colistin susceptibility testing ; Disk diffusion ; Muller-Hinton agar ; Protamine
Abstract
Background: Colistin has become a last-resort antibiotic for the management of multidrug-resistant gram-negative bacteria. The disk diffusion test is cheap and easy to perform but may be unreliable for colistin susceptibility testing due to poor diffusion of the large colistin molecule. An improved agar diffusion test would increase the reliability of colistin susceptibility testing. This study aimed to modify Muller-Hinton agar (MHA) to improve colistin diffusion in agar.

Methods: MHA was modified by reducing the agar concentration from 100% to 30% and supplementing with protamine. We tested 60 gram-negative clinical isolates of Pseudomonas aeruginosa (N=27) and Acinetobacter calcoaceticus-baumannii complex (N=33). Disk diffusion test results were interpreted based on minimum inhibitory concentrations determined by broth microdilution.

Results: The modified MHA yielded the best performance metrics, including 94.7% sensitivity, 100% specificity, and an area under the curve of 0.995 (95% confidence interval, 0.982-1.000), P<0.001, at a cut-off point of 13 mm.

Conclusions: A reduction of the agar concentration from 100% to 30% and the addition of protamine improved colistin diffusion in agar and allowed routine colistin susceptibility testing in a clinical microbiology laboratory, but should be handled with caution.
Files in This Item:
T202002558.pdf Download
DOI
10.3343/alm.2020.40.4.306
Appears in Collections:
1. College of Medicine (의과대학) > Dept. of Laboratory Medicine (진단검사의학교실) > 1. Journal Papers
Yonsei Authors
Kim, Daewon(김대원) ORCID logo https://orcid.org/0000-0002-3487-5943
Byun, Jung-Hyun(변정현)
Yong, Dong Eun(용동은) ORCID logo https://orcid.org/0000-0002-1225-8477
URI
https://ir.ymlib.yonsei.ac.kr/handle/22282913/179507
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