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 Methicillin-resistant Staphylococcus aureus (MRSA), Enterococcus faecalis, S. 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.