Nigella sativa Seed Oil Antibacterial and Antibiofilm Activity against Escherichia coli O157H7 Shiga Toxin-2.

Shiga toxin type 2 (Stx2)-producing Escherichia coli O157H7 has become a global risk to public health. The study aimed to investigate the emergence of antimicrobial resistance patterns in the clinical isolates of E. coli. The isolates revealed a pattern of strong resistance to the majority of the common antibiotics. Most E. coli isolates were susceptible to gentamicin and were classified as MDR. The Stx2 determinant was screened in E. coli O157:H7 isolates through the PCR technique, and the Stx2 was purified by cation exchange and gel filtration chromatography. The purification yielded 5.2 milligrams of pure Stx2. Nigella sativa oil's obtained by the mechanical expression of seeds at room temperature was evaluated for its antibacterial activity against 16 E. coli O157:H7 isolates at different concentrations. The oil induced inhibition zone diameter of 9.83, 16.71, and 27.48 mm at the concentration of 16, 32, and 64 μg/mL, respectively. Minimum inhibitory concentration (MIC) of N. sativa seed oil (NSSO) and gentamicin-treated biofilm-forming different isolates ranged from 64-502 and 32-256 μg/mL, respectively. Optical density (O.D.) and viable counts showed significant differences before and after the treatment with sub-MIC. The injections of Stx2 caused microangiopathy in mice, including hemolytic anemia, thrombocytopenia, and renal impairment. The Stx2 also caused microvascular thrombosis and other histologic damage in the kidney, spleen, and liver, as well as a significant reduction in the splenic size of the infected mice. The results showed that the variance in the values of the complete blood count, as well as histopathological alteration in the spleen, occurred in mice treated with Nigella sativa oil, which was improved compared with the control. This study is the first report on NSSO exhibiting inhibitory activity on E. coli and its Shiga toxin, which can also inhibit virulence in E. coli, thereby suggesting it as an alternative for therapy.