Table 1.
Properties of synthetic peptides.
Table 2.
Minimum Inhibitory Concentration (MIC) values of test peptides (2Abz14S29, 2Abz23S29, and HNP-1ΔC18A) and antibiotics (amoxicillin, ciprofloxacin, cefixime, and norfloxacin) against standard and clinical E. coli isolates.
Fig 1.
Fractional Inhibitory Concentrations (FICs) plot for 2Abz14S29, 2Abz23S29, and HNP-1ΔC18A combination against CFT073 uropathogenic E. coli.
A) The ΣFIC by the 2Abz14S29 and 2Abz23S29 is (15.62/62.5) + (31.25/125) = 0.5, B) The ΣFIC by the 2Abz14S29 and HNP-1ΔC18A is (15.25/62.5) + (62.5/125) = 0.75, C) The ΣFIC by the 2Abz23S29 and HNP-1ΔC18A is (15.25/62.5) + (62.5/125) = 0.75, MIC: minimal inhibitory concentration. ΣFIC ≤ 0.5, synergistic; 1>ΣFIC> 0.5, additive; 1< ΣFIC> 4.0, indifference, ΣFIC> 4.0, antagonistic.
Fig 2.
Fractional Inhibitory Concentrations (FICs) indices of combinations consisting of antibiotics and either of three antimicrobial peptides against MDR clinical E. coli isolates (n = 20).
Black dashed line denotes the cutoff FICindex of ≤0.5 for synergistic interaction. FICindex≤0.5, synergistic; 1>FICindex>0.5, additive; 1<FICindex>4.0, indifference, FICindex>4.0 antagonistic. See Supplementary Material (S1 and S2 Tables) for MIC and FIC values.
Fig 3.
Killing kinetics of 2Abz14S29, 2Abz23S29, and HNP-1ΔC18A against multidrug-resistant E. coli.
Bacteria were incubated with the peptides at concentrations equal to their MICs for different times. Control represents untreated bacteria. Data are expressed as mean of at least two independent experiments.
Fig 4.
Biofilm inhibition by individual antimicrobial peptides (2Abz14S29, 2Abz23S29, and HNP1ΔC18A), antibiotics (Cefixime and Amoxicillin) or their combination are shown in panels A, B, and C. Untreated bar indicates E. coli biofilm without any antimicrobial agent. Data show the means ± SD of three independent experiments. An asterisk indicates the statistically significant difference between antimicrobial agent and untreated control as measured by Student’s t-test (*p < 0.05, **p < 0.01 and ***p < 0.001). Percent numbers indicate % reduction of biofilm.
Fig 5.
Biofilm eradication by individual antimicrobial peptides (2Abz14S29, 2Abz23S29, and HNP1ΔC18A), antibiotics (Cefixime and Amoxicillin) or their combination are shown in panels A, B, and C. Untreated bar indicates E. coli biofilm without any antimicrobial agent. Data show the means ± SD of three independent experiments. An asterisk indicates the statistically significant difference between antimicrobial agent and untreated control as measured by Student’s t-test (*p < 0.05, **p < 0.01 and ***p < 0.001). Percent numbers indicate % reduction of biofilm.