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. 2024 May 2;13(5):418.
doi: 10.3390/antibiotics13050418.

Flow Cytometry as a Rapid and Valuable Method in Investigation of Colistin Resistance in Carbapenem-Resistant Klebsiella pneumoniae Isolates

Şafak Ceren Uçak  1   2 , Betigül Öngen  1
Affiliations

Flow Cytometry as a Rapid and Valuable Method in Investigation of Colistin Resistance in Carbapenem-Resistant Klebsiella pneumoniae Isolates

Şafak Ceren Uçak et al. Antibiotics (Basel). .

Abstract

Rapid detection of antimicrobial resistance is crucial for early initiation of appropriate therapy. The aim of this study was to investigate whether resistance to colistin, the last-resort antibiotic, in carbapenem-resistant Klebsiella pneumoniae (CRKP) isolates can be detected accurately and rapidly by flow cytometry (FCM). The VITEK 2 automated system was used to identify 85 K. pneumoniae strains and to determine their resistance to carbapenems. The minimum inhibitory concentration (MIC) values for colistin in 85 CRKP strains were determined by broth microdilution (BMD), which is the reference method. In addition, FCM was used, combined with DiBAC4(3) fluorescent stain, to determine colistin susceptibility. The MIC₅₀ value of the strains, 80% of which were resistant to colistin by the BMD method, was 16 mg/L, and the MIC₉₀ value was 32 mg/L. When FCM was compared with the reference method, it was determined that the specificity was 94.1%, sensitivity was 100% of FCM, and Cohen's kappa value was 0.96. Colistin susceptibility results with FCM were obtained within an average of 2 h. These findings suggest that FCM holds great promise as a rapid and reliable alternative method for detecting colistin resistance in CRKP strains.

Keywords: DiBAC4(3); Klebsiella pneumoniae; MIC; colistin; flow cytometry.

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Conflict of interest statement

The authors declare no conflicts of interest.

Figures

Figure 1
Figure 1
Overlay graph of the isolate with a major error (blue indicates results for the growth control tube; red, 1 mg/L; green, 2 mg/L; and yellow, 4 mg/L colistin containing tube).
Figure 2
Figure 2
Overlay graphs of the reference strains (E. coli NCTC 13846 (mcr-1+), E. coli ATCC 25922) and the clinical strains with MIC values of 512 mg/L (R) and 1 mg/L (S). (A) indicates the results for resistant strains; blue indicates the growth control tube; red, 1 mg/L; green, 2 mg/L; and yellow, 4 mg/L indicate the tube containing colistin. (B) indicates the results for sensitive strains; blue indicates the growth control tube; red, 0.5 mg/L; green, 1 mg/L; and yellow, 2 mg/L indicate the tube containing colistin.
Figure 3
Figure 3
Dot plot graph of the gating process of cells stained with fluorescent dye (7-AAD) in the SSC/PC5 channel of K. pneumoniae strain.
See this image and copyright information in PMC

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