Dispersal of pathogen‐associated multispecies biofilm by novel probiotic Bacillus subtilis in a contact‐dependent manner

Aims Biofilms are involved in pathogenesis of various bacterial infections. Treatment of biofilm‐related bacterial infection remains a major challenge due to the reduced efficacy of antibiotics and associated antibiotic resistance. Given the high prevalence of Enterotoxigenic Escherichia coli (ETEC), Salmonella Typhimurium (S. Typhimurium) and methicillin‐resistant Staphylococcus aureus (MRSA)‐related infections and associated drug resistance, it is imperative to develop alternative strategies for treatment and prevention. The current study investigated antibiofilm activity of a recently isolated Bacillus subtilis (B. subtilis‐9) against these pathogens. Methods and Results Crystal violet staining showed that treatment with B. subtilis‐9 significantly reduced biofilm biomass of ETEC (60%–80%), S. Typhimurium (68%–73%) and MRSA (66%–82%). In addition, B. subtilis‐9 significantly reduced pre‐formed biofilm biomass of ETEC (59%), S. Typhimurium (62%), MRSA (65%) and multispecies (58%). Fluorescence microscopy revealed that B. subtilis‐9 treatment significantly reduced the thickness of biofilm and viability of the embedded bacteria. Additionally, B. subtilis‐9 significantly reduced planktonic cell growth of ETEC (92%), S. Typhimurium (94%) and MRSA (93%). Interestingly, transwell assay showed that B. subtilis‐9 exhibited antibiofilm properties in a cell‐to‐cell contact‐dependent manner and significantly reduced mRNA expression of biofilm‐related genes, bssS, luxS and ihfB in ETEC. Conclusion Novel B. subtilis‐9 exhibits a strong inhibitory activity against ETEC, S. Typhimurium and MRSA biofilm formation and adhesion to abiotic surfaces. With further investigations, our study could bring forward a novel Bacillus‐based probiotic intervention strategy to combat pathogenic biofilms, in clinical and agricultural settings. Significance and Impact of the Study Probiotic bacteria propose a potential alternative in combating biofilm‐related infections, however, data on the efficacy and strain selection are limited. Data from this study are critical in further developing Bacillus‐based novel probiotic applications that may reduce the use of antibiotics in biofilm‐related infections in humans and animals.