Inhibitory Effect of Terminalia chebula Retz. on MDR Shigella flexneri Invasion of HeLa Cells

Shigella flexneri causes bacillary dysentery by invading the colon epithe-lium, leading to inflammation and tissue damage. The emergence of multidrug-resistant (MDR) Shi-gella strains and the lack of effective vaccines have highlighted the need for alternative treatments. Natural plant compounds have been explored as potential antimicrobial agents. This study evaluates the antibacterial activity of ethanolic (70%-96%) and methanolic (70%-99.9%) extracts of Termi-nalia chebula Retz. against MDR S. flexneri and their effect on bacterial invasion of HeLa cells in vitro. We assessed the anti-MDR S. flexneri activity of these extracts by measuring minimum inhib-itory concentration (MIC) and minimum bactericidal concentration (MBC).

Four Shigella strains belonging to various serotypes and resistant to multiple drugs were used in this study. The invasiveness of S. flexneri was assayed by plaque formation in HeLa cell culture under in vitro conditions. Ethanolic and methanolic extracts of Terminalia chebula Retz. were made in varying concentrations. The antibacterial effects of these extracts against MDR S. flexneri strains were evaluated by determining minimum inhibitory concentration (MIC) and min-imum bactericidal concentration (MBC).

Plaque-forming assay confirmed that all four S. flexneri serotypes were highly invasive in HeLa cells. All the compounds screened herein were found to be antibacterial (MIC = 0.39-12.5 mg/mL) and (MBC = 0.78-25 mg/mL) against the multidrug-resistant invasive S. flexneri strain, while the MBC/MIC ratio showed both bactericidal and bacteriostatic activity.

Shigella species are highly infectious and increasingly multidrug-resistant pathogens with significant invasive potential in intestinal cells, as confirmed by our HeLa cell plaque assay results, consistent with prior studies. Our investigation indicates that Terminalia chebula Retz. ex-tracts may exhibit antibacterial activity against multidrug-resistant invasive Shigella isolates. Com-parable research has reported similar antimicrobial effects of T. chebula against various resistant bac-teria, including Shigella sonnei, MRSA, and MDR Escherichia coli. While some studies found other plant extracts, such as Rhus javanica, more potent, bioactive compounds of T. chebula, such as gallic acid derivatives, support its promising role in combating antibiotic-resistant infections.

These findings suggest that ethanolic and methanolic extracts of Terminalia chebula may have antimicrobial activity against multidrug-resistant and invasive Shigella flexneri. These pre-liminary results indicate that T. chebula extracts warrant further exploration as potential antimicrobial agents against MDR Shigella infections. However, given the limited sample size in this study, further research with larger and more diverse strains is necessary to confirm the therapeutic potential of these plant extracts.