Alpha-bisabolol from brown macroalga Padina gymnospora mitigates biofilm formation and quorum sensing controlled virulence factor production in Serratia marcescens

Biofilm formation, quorum sensing (QS)-regulated virulence and emergence of antibiotic resistance in bacterial pathogens lead to major health problems. In this perspective, antibiofilm agents and QS inhibitors have gained much attention to treat infections caused by antibiotic-resistant pathogens. For the first time, this investigation reports the antibiofilm and QS inhibitory potential of the brown macroalga Padina gymnospora against the nosocomial pathogen Serratia marcescens. The methanolic extract of P. gymnospora inhibited biofilm formation and the production of prodigiosin and protease. Successive solvent extraction, bioassay-guided fractionation of chloroform extract and GC-MS analysis of active fractions showed the presence of alpha-bisabolol with a relative abundance of 69 %. In vitro assays with alpha-bisabolol evidenced the potent inhibition of biofilm and QS-controlled prodigiosin, protease and swarming in S. marcescens, without exerting deleterious effect on its growth and metabolic activity. The results of this study exemplify the use of P. gymnospora and alpha-bisabolol as promising alternatives to antibiotics.