Biofilm Effects of the Soil Bacillus cereus Metabolites: Isolation, Characterization and Antimicrobial Activity Against Methicillin-Resistant Staphylococcus aureus

The methicillin-resistant Staphylococcus aureus (MRSA) causes serious health problems such as community-acquired infections and nosocomial infections, posing a significant public health threat worldwide. The ability of MRSA to adhere to host tissues and medical implants form a mature biofilm that effectively covers host cells in a polymer-based matrix leads to the deduction in the host-immune defences, antimicrobial therapy and difficulty in disease eradication. The present investigation mainly focusing the isolation of the bacteriocin producing microbes from soil and testify their biofilm inhibition ability against MRSA. Bacteriocin-producing bacteria are identified by utilizing nutritious agar media and the agar well-diffusion bioassay in the presence of MRSA as an indicator organism. The 16S rDNA gene sequencing, molecular weight identification and antibiofilm activity showed the four isolates (PU1, PU2, PU3, and PU4) produce bacteriocin and have a wide-ranging antagonistic activity against MRSA. Among them, PU3 exhibits maximum inhibitory activity against MRSA at 100AU/mL concentration using agar well diffusion method. The biochemical assay and 16S rDNA sequencing confirm the isolate PU3 affirmed as Bacillus cereus with a molecular weight of ~ 3 kDa. In situ zymogram assay showed a zone of inhibition corresponding to the estimated protein band size and Time-kill study also displayed that B. cereus producing metabolites (bacteriocin) comprises a bactericidal effect and 90% reduction in biofilm biomass toward MRSA. This study showed that soil isolated bacteria-based antimicrobial compounds control microbial infections and may instruct future antibacterial research.