Figure 6 After imipenem addition, changes in the 3-hydroxy-2-butanone (acetoin) content emitted by various carbapenase types of K. pneumoniae strains (clinical isolates) at the T2 time point. (A) The pseudo-3D plots of 3-hydroxy-2-butanone (acetoin) in different carbapenase types of K. pneumoniae strains after the addition of imipenem. VOCal (version 0.1.3), G.A.S., Shandong HaiNeng Scientific Instrument Co., Ltd., Shandong, China. (B) Comparison of the relative peak volume (semiquantitative) of 3-hydroxy-2-butanone (acetoin) emitted by different carbapenase types of K. pneumoniae strains after the imipenem addition. The free online tool Chiplot (https://www.chiplot.online). The Mann-Whitney U test was used for pairwise comparison. **** P<0.0001. R version 4.2.3, The R Foundation, Vienna, Austria. K. pneumoniae – Klebsiella pneumoniae; CSKP – carbapenem-susceptible Klebsiella pneumoniae; CRKP – carbapenem-resistant Klebsiella pneumoniae; KPC – Klebsiella pneumoniae-carbapenemases; NDM – New Delhi metallo-β-lactamase; IMP – imipenemase metallo-β-lactamase.