Fig 1.
MIC of E. coli during sub-MIC concentrations exposed.
The results illustrate the MIC progression of bacterial strains exposed to 1.1 mg.L-1 colistin over 10 consecutive cycles, followed by an eleventh cycle (C11) at an elevated concentration of 6.4 mg.L-1. The purple squares represent the MIC values of the strain undergoing subinhibitory colistin exposure, while the gray circles denote the control strain#39;s MIC values. The hatched square indicates the clinical breakpoint range of 2-4 mg/L, as established by BrCAST guidelines [13,21].
Fig 2.
MIC profiles of Escherichia coli strains across six consecutive antibiotic-free growth cycles.
(A) MIC for colistin; (B) MIC for ceftazidime; (C) MIC for gentamicin. Strains evaluated: E. coli ATCC 25922 (susceptible control – blue triangles), E. coli C11 (colistin-induced resistant strain – light purple circles), E. coli CCBH 20178 (clinical multidrug-resistant isolate – dark purple squares). Data represents the mean values of three independent biological replicates. Different letters indicate statistically significant differences, as determined by Kruskal-Wallis ANOVA (p < 0.05).
Fig 3.
(A): Bacterial growth curve for the E. coli strains (ATCC 25922), E. coli (C 11), and the E. coli strain (CCBH20178). (B): Bacterial growth curve of de logarithmical phase for the E. coli strains (ATCC 25922), E. coli (C 11), and the E. coli strain (CCBH20178).
Table 1.
Growth rate and duplication time of E. coli strain.
Fig 4.
Phenotypic evaluation of the E. coli strains. The colistin sulfate MIC results in MHCA (cation-adjusted Mueller-Hinton broth, blue bars) and calcium chloride-enriched MHCA (5 mM) (purple bars) for E. coli strains (ATCC 25922), E. coli (C 11), and E. coli (CCBH 20178). Group C1 represents strains after one antimicrobial-free growth cycle, while group C5 shows results after five antibiotic-free growth cycles. Phenotypic detection of mcr-1 was inferred from the MIC profiles and annotated above the bars as mcr-1(+) or mcr-1(–).
Fig 5.
Environmental toxicity of colistin.
(A) Macroscopic parameters of A. cepa seed germination and early development exposed to different concentrations of colistin, represented by the germination index and root elongation index. (B) Microscopic parameters, including the chromosomal aberration index, micronucleus index, and mitotic index. Data are presented as mean ± standard error (SE). Different letters above the bars indicate significant differences between treatments according to one-way ANOVA followed by Tukey’s post hoc test (p < 0.05).