Chronic wounds are frequently colonized by bacteria, including Escherichia coli, and hypertonic sodium chloride has been proposed as a topical antibacterial agent. This study aimed to evaluate the in vitro antibacterial activity of 7%, 10%, and 13% sodium chloride solutions against E. coli. Activity was assessed by agar well diffusion on Mueller–Hinton agar, with sterile distilled water as the negative control and an amoxicillin disc as the positive control (three replicates per group). The net inhibition zone was calculated as the mean of two diameter readings minus the well or disc diameter. Groups were compared by one-way analysis of variance (ANOVA) with Tukey’s post hoc test, and the Kruskal–Wallis test with Dunn’s test served as a sensitivity analysis. The 7%, 10%, and 13% sodium chloride solutions produced mean net zones of 3.86 ± 2.08, 5.68 ± 1.54, and 4.19 ± 1.35 mm, respectively, compared with 0.00 mm for distilled water and 26.20 ± 1.78 mm for amoxicillin (ANOVA, p < 0.001). The 10% and 13% solutions differed from the negative control (p = 0.007 and p = 0.046), whereas the 7% solution did not (p = 0.068), and the three concentrations did not differ from one another. In the sensitivity analysis, no sodium chloride solution differed from the negative control. Under these conditions, hypertonic sodium chloride showed at most weak inhibition of E. coli, and its value as an antibacterial agent for chronic wounds remains unproven.
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