Antibacterial and anti-parasitic activities of Terfezia claveryi methanolic extract against some common pathogenic agents of infectious diarrhea

Objective: To assess the antidiarrheal effects of Terfezia claveryi methanolic extract against Escherichia coli, Salmonella typhimurium, Shigella flexneri, and Giardia lamblia. Methods: Antibacterial effects of the Terfezia claveryi methanolic extract were carried out by determining the minimum inhibitory concentration (MIC) and minimum bactericidal concentration through micro broth dilution technique. Furthermore, reactive oxygen species production and protein leakage were evaluated. To evaluate the in vitro anti-giardial effects of Terfezia claveryi methanolic extract, Giardia lamblia WB (ATCC® 30957) trophozoites were treated with various concentrations of Terfezia claveryi methanolic extract for 10-360 min. In addition, the plasma membrane permeability of trophozoites treated with Terfezia claveryi methanolic extract was determined. The cytotoxicity effects of Terfezia claveryi methanolic extract against normal (HEK293T) and cancer (MCF-7) cells were also assessed using the MTT assay. Results: The MIC and minimum bactericidal concentration of Terfezia claveryi methanolic extract against bacterial strains were in the range of 0.52-1.04 and 1.04-2.08 mg/mL, respectively. The results revealed that reactive oxygen species production and protein leakage were significantly increased after the bacteria were treated with the Terfezia claveryi methanolic extract, especially at 1/3 and 1/2 MICs (P<0.001). Furthermore, Terfezia claveryi methanolic extract decreased the viability of Giardia lamblia trophozoites in a dose-dependent manner. Terfezia claveryi methanolic extract at 1, 2, and 4 mg/mL resulted in 100% mortality in Giardia lamblia trophozoites after 360, 240, and 120 min, respectively. Moreover, Terfezia claveryi methanolic extract altered the permeability of plasma membrane of Giardia lamblia trophozoites by increasing the concentration. MTT assay revealed that the 50% cytotoxic concentrations values for HEK293T and MCF-7 cells were 4.32 mg/mL and 6.40 mg/mL, respectively, indicating that Terfezia claveryi methanolic extract had greater cytotoxicity against cancer cells than normal cells. Conclusions: Terfezia claveryi methanolic extract had potent in vitro antibacterial and anti-parasitic effects on Escherichia coli, Salmonella typhimurium, Shigella flexneri, and Giardia lamblia by affecting cell membrane permeability and reactive oxygen species generation with no significant cytotoxicity on normal cells.