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The following is a summary of “Use of MALDI-TOF VITEK MS for rapid and efficient identification of KPC-type carbapenemases in Enterobacterales carrying the Tn4401a transposon,” published in the April 2025 issue of European Journal of Clinical Microbiology & Infectious Diseases by Montaño et al. 

Researchers conducted a retrospective study to evaluate the diagnostic validity of Matrix-assisted laser desorption ionization–time of flight mass spectrometry (MALDI-TOF MS) (VITEK MS) in detecting Klebsiella pneumoniae carbapenemases (KPC)-type carbapenemases by identifying the 11,109 Dalton (Da) peak, comparing its performance with RAPIDEC^®  CARBA NP, modified carbapenemase inactivation method (mCIM), and EDTA-modified carbapenem inactivation method (eCIM) in previously characterized isolates.  

They analyzed 210 Enterobacterales clinical strains with the bla_KPC gene, pKpQIL plasmid, and Tn4401a transposon, including 34 carbapenemase-producing Klebsiella pneumoniae (Tn4401a-associated), 30 bla_KPC -positive Enterobacterales (unknown plasmid background), and 146 negative controls. Accuracy and agreement were assessed for VITEK MS, RAPIDEC ^®  CARBA NP, and mCIM/eCIM tests and ROC curves were compared.   

The results showed that the 11,109 Da peak was detected in 100% of KPC Tn4401a-positive isolates using VITEK MS, with 100% sensitivity (95% CI: 98.53–100), 95.5% specificity (95% CI: 91.7–99.4), 85.0% positive predictive value (PPV) (95% CI: 72.7–97.3), 100% negative predictive value (NPV) (95% CI: 99.6–100), and 22.3 positive likelihood ratio (PLR) (10.2–48.8). The agreement among VITEK MS, RAPIDEC ^®  CARBA NP, and mCIM/eCIM tests was 93.3%, with a Kappa index of 0.90 (95% CI: 0.83–0.97, P ≤ 0.05). The ROC curves showed areas under the curve (AUCs) of 0.95, 0.96, and 0.96 for VITEK MS, RAPIDEC^®  CARBA NP, and mCIM/eCIM, respectively.  

Investigators concluded that the detection of the 11,109 Da peak by Vitek MS demonstrated the presence of KPC-type carbapenemase, enabling rapid and simultaneous detection with species identification, while a negative result necessitated further testing to exclude the enzyme’s presence. 

Source: link.springer.com/article/10.1007/s10096-025-05097-6