Antibacterial and wound healing potential of topical formulation of marine symbiotic Bacillus

The inevitability to develop novel antimicrobial agents has considerably increased because of mounting alarms concerning multidrug-resistant microbial strains. The present study evaluated an antibacterial and wound healing topical formulation prepared with the ethyl acetate extract of marine symbiotic Bacillus amyloliquefaciens MTCC 12716 as the basic ingredient and the grafted macroalgal polysaccharide as the gel base with an appropriate proportion of natural stabilizing agents. The formulation exhibited potent antibacterial activities against clinical isolates of Staphylococcus aureus (18 mm inhibition zone) and Pseudomonas aeruginosa (19 mm) causing infection when compared with commercially available antimicrobial cream clindamycin. The in-vitro results indicated that the organic extract of B. amyloliquefaciens MTCC 12716 at its MIC and the formulation sealed the wound by 78 and 94%, respectively, at 48 h in the scratch-induced L929 cells, compared to 84% exhibited by clindamycin. The topical formulation of marine symbiotic Bacillus induced greater than 80% viability of the normal fibroblasts compared to 78% exhibited by clindamycin, when administered at a dose of 25 μg mL^-1. The studied antibacterial formulation could accelerate the wound healing by prompting the migration of fibroblasts towards the artificially created wound resulting in rapid wound closure, and at an even higher concentration of formulation, it displayed no cytotoxicity on L929 cells. The stability studies showed that the formulation maintained its physicochemical characteristics and minimal growth (<10 cfu g^-1) of bacteria on the plates throughout the time period of 18 months at 30 °C and 65% relative humidity. This study has established the antibacterial and wound healing potential of a topical formulation of marine symbiotic B. amyloliquefaciens.