Evaluation of Anti-bacterial, Anti-adenoviral, and Apoptosis-inducing Activity of Bacillus clausii Supernatant

Abstract

Background: Bacillus clausii is being studied as a probiotic candidate. There is insufficient information on the antimicrobial and anticancer effects of B. clausii. Objectives: The present investigation was designed to evaluate the anti-bacterial, anti-adenoviral, and apoptosis-inducing activity of B. clausii cell-free supernatant (CFS). Methods: First, the supernatant of B. clausii was collected after culture for 24 h. Then, its anti-bacterial impact on several genera of bacteria was assessed through the minimal inhibitory concentration (MIC) and minimal bactericidal concentration (MBC). Adenovirus 5 (Ad5) was exposed to the CFS under four conditions, including pre-treatment: first infecting cells with CFS and then with the virus; pre-incubation: incubation of the supernatant and virus for 1.5 hours and then adding to the cells; competition: infection of cells with the simultaneous mixture of the supernatant and virus, and post-treatment: first infecting cells with the virus and then with CFS. The median tissue culture infectious dose (TCID50) technique determined the virus titer. Real-time PCR was performed to assess the E1A expression. After exposure to the CFS, real-time PCR was utilized to measure the expression of MicroRNA-145, BCL-2, and BAX in HeLa cancer cells. Results: Bacillus clausii supernatant showed an inhibitory effect on MRSA, Enterococcus faecalis, Staphylococcus aureus, Pseudomonas aeruginosa, Escherichia coli, and Acinetobacter. baumannii. The Ad5 titers were reduced by about 4.61, 4, 3.9, and 3.1 Log10 TCID50/mL in pre-treatment, pre-incubation, competition, and post-treatment tests (CFS dilution: 1/4), respectively. Similar results of the viral titration were seen when experimental and control E1A expression levels were compared. Also, B. clausii supernatant during 48 h exposure to HeLa cells increased the transcript of the BAX, BCL-2, and miR-145 genes to 9.1, 2.3, and 55 folds, respectively, compared to the untreated condition. Conclusions: Bacillus clausii can be a potent antimicrobial and anticancer agent. Further research is required to learn about the spectrum of anti-bacterial, antiviral, and anti-cancerous activities of B. clausii.