Antimicrobial Susceptibility Testing for Colistin: Extended Application of Novel Quantitative and Morphologic Assay Using Scanning Electron Microscopy

Figure 3

Colistin SEM-AST assay applied to Colistin-sensitive and Colistin-resistant strains of Enterobacter cloacae. (a) Evolution of the percentage of viable bacteria for Colistin-resistant strains exposed to Colistin for 120 minutes. (b) SEM images of Colistin-resistant strains exposed to Colistin for 120 minutes. (c) Evolution of the percentage of viable bacteria for Colistin-sensitive strains exposed to Colistin for 120 minutes. (ns: not significant / ^∗∗∗: p ≤ 0.001/ ^∗∗∗∗: p ≤ 0.0001) (d) SEM images of Colistin-sensitive strains exposed to Colistin for 120 minutes demonstrating morphologic changes (dysmorphism (red arrow), inflation (blue arrow), and lysis (orange arrow)).

(a)

(b)

(c)

(d)