Abstract:

Objective To investigate the accuracy and clinical application role of direct-on-target microdroplet growth assay（DOT-MGA） based on matrix-assisted laser desorption ionization time-of-flight mass spectrometry（MALDI-TOF MS） for rapid determination of carbapenem-resistant Klebsiella pneumoniae（CRKP）. Methods A total of 251 clinical Klebsiella pneumoniae isolates were collected from the First Hospital of Lianyungang from 2020 to 2021，which included 123 meropenem-sensitive isolates and 128 CRKP isolates. The carbapenem resistance of all the isolates was determined by DOT-MGA with 2 sample sizes of 4 and 6 μL，and the minimum inhibitory concentration（MIC） of meropenem of each isolate was determined by broth microdilution method. Using the results of broth microdilution method as reference，the accuracy of DOT-MGA drug resistance results was evaluated. Results With the broth microdilution method as reference，the sensitivity and negative predictive value of DOT-MGA were 100.0% after incubation and growth for 4 h，and the specificity and positive predictive value of 4 μL group were 92.5% and 92.8%，respectively. The specificity and positive predictive value of 6 μL group were 89.8% and 90.1%，respectively. The MIC₅₀ of 123 meropenem-sensitive isolates was 0.125 μg·mL^-1，and the MIC₉₀ was 0.25 μg·mL^-1. The MIC₅₀ of 128 meropenem-resistant isolates was ≥128 μg·mL^-1，and the MIC₉₀ was ≥128 μg·mL^-1 as well. The consistency analysis results of DOT-MGA and broth microdilution method showed that the Kappa value of 4 μL group was 0.88，and that of 6 μL group was 0.83. Conclusions DOT-MGA based on MALDI-TOF is a simple，rapid and accurate method for the determination of CRKP，which can be used in the rapid determination of CRKP in clinical practice.

Key words: Carbapenem-resistant Klebsiella pneumoniae, Matrix-assisted laser desorption ionization time-of-flight mass spectrometry, Direct-on-target microdroplet growth assay, Broth microdilution method