Publication
Title
Evaluation of colistin stability in agar and comparison of four methods for MIC testing of colistin
Author
Abstract
Susceptibility testing for colistin remains challenging primarily due to its inherent properties. We evaluated colistin stability in agar and reproducibility of colistin MICs obtained by agar dilution, broth macro- and micro-dilution and MIC gradient strips on 3-7 iterations of each method using clinical Klebsiella pneumoniae (susceptible-CS, and resistant-CR, n = 2 each), mcr-harboring Escherichia coli (n = 2), and reference strains E. coli ATCC25922 and Pseudomonas aeruginosa ATCC27853. MICs for reference strains were not in the given range using Etest and broth microdilution (ATCC25922, 0.125 and 4 mu g/ml, respectively). MICs of CR-1 and CR-2, and of the mcr-harboring E. coli showed high concordance between agar and broth dilution varying up to one 2-fold dilution. However, remarkable variations were observed on broth dilution with CS-1 and CS-2 (MIC range 0.25-32 and 0.5-64 mu g/ml, respectively); whereas for agar dilution the MIC for both CS strains was 0.5 mu g/ml in all the runs. MICs obtained by MIC gradient strips were lower than those obtained by dilution methods (1-2 dilutions for CS and mcr strains, and up to five dilutions for CR strains). To confirm uniform distribution of colistin in agar, a single strain was spotted in five different regions of the same plate. All spots showed concordant growth with maximum one dilution difference. No effect on MIC was found due to storage of colistin-containing agar plates for 7 days at 4 degrees C. In our hands, agar dilution was superior in terms of reproducibility and robustness, compared to broth dilution methods, for colistin MIC determination.
Language
English
Source (journal)
European journal of clinical microbiology and infectious diseases. - Wiesbaden
Publication
Wiesbaden : 2018
ISSN
0934-9723 [print]
1435-4373 [online]
DOI
10.1007/S10096-017-3140-3
Volume/pages
37 :2 (2018) , p. 345-353
ISI
000423152100021
Pubmed ID
29177612
Full text (Publisher's DOI)
Full text (open access)
UAntwerpen
Faculty/Department
Research group
Project info
Resistance in gram-negative organisms: studying intervention strategies (R-GNOSIS).
Mechanistic insights on colistin resistance in pathogenic Escherichia coli and Klebsiella species.
Publication type
Subject
Affiliation
Publications with a UAntwerp address
External links
Web of Science
Record
Identifier
Creation 08.02.2018
Last edited 09.10.2023
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