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 pL,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 pg·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.
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