Figure 4: Morphological changes of E. coli after treatment with mezlocillin FSC-SSC-Dot plot of E. coli isolate 247 after 120 min incubation with cefazolin (A) or mezlocillin (B). Fluorescence microscopy of E. coli isolate 247 with cefazolin (C) or mezlocillin (D), colored with DiBAC4(3) (100er optical enlargement, spot, light exposure 3 s). Cefazolin, in contrast to mezlocillin, lead to filamentous elongation of bacterial cells.