Figure 4 The changes in 3-hydroxy-2-butanone (acetoin) contents emitted by standard strain at the T2 time point before and after the addition of imipenem. (A) The pseudo-3D plots of 3-hydroxy-2-butanone (acetoin) in each standard strain (comparison between no addition of imipenem and imipenem addition). 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 standard strains (with imipenem and without imipenem). The free online tool Chiplot (https://www.chiplot.online). The Mann-Whitney U test was used for pairwise comparison. * P<0.05, ** P<0.01, *** P<0.001, and **** P<0.0001. R version 4.2.3, The R Foundation, Vienna, Austria. ATCC – American Type Culture Collection; IPM – imipenem.