Targeting Staphylococcus aureus and its biofilms with novel antibacterial compounds produced by Lactiplantibacillus plantarum SJ33

The emergence of microbial resistance to conventional antibiotics, partially attributed to biofilm formation, has urged for new antimicrobial compounds. Here, we reported two novel low molecular weight (LMW) compounds from Lactiplantibacillus plantarum SJ33 and evaluated their biofilm inhibitory effects on Staphylococcus aureus. The compounds C1 and C2 were purified by RP-HPLC and structurally identified as 3-amino-5-hydroxy-6-(hydroxymethyl)-4-(1-hydroxyprop-2-yn-1-yl)-3,3a,4,5,6,7a-hexahydro-7H-indazol-7-one and 1-(dimethylamino)-3-hydroxy-3-((2-hydroxypropan-2-yl)oxy)-1-(methylamino)-butan-2-one by spectroscopic techniques. High ESI–MS data confirmed the molecular weight of C1 and C2 as 254.1141 and 234.1658 Da, respectively. Time-kill assay demonstrated bactericidal action of compounds, whereas scanning electron microscopy revealed morphological changes in treated S. aureus MTCC96 and methicillin-resistant S. aureus (MRSA) cells. The antibacterial compounds reduced biofilm formation in S. aureus MTCC96 and MRSA by crystal violet assay. Further, fluorescence and scanning electron microscopic images exhibited biofilm formation by pathogens and biofilm inhibition by compounds treatment. The Quantitative RT PCR revealed the down-regulation of icaC and icaD genes involved in intercellular adhesion of biofilms. The results confirmed the anti-biofilm activity of novel LMW compounds by eliminating preformed biofilms formed by S. aureus MTCC96 and MRSA.