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.

Inhibiting bacterial colonization on catheters: Antibacterial and antibiofilm activities of bacteriocins from Lactobacillus plantarum SJ33.

BACKGROUND: Catheter-associated urinary tract infections are one of the most common types of hospital-acquired infections that start with bacterial adhesion and lead to biofilm formation. The antagonistic activity of lactic acid bacteria against pathogenic organisms makes them important for medical applications. OBJECTIVE: This study evaluated the precise method for purification of bacteriocin from Lactobacillus plantarum subsp. argentoratensis SJ33, and its characterization and effectiveness for biofilm inhibition on urinary catheters coated with bacteriocin. METHODS: Purification of bacteriocin was carried out using various methods such as cell adsorption-desorption, gel permeation chromatography, and hydrophobic interaction chromatography. Bacteriocin preparation was analysed using reverse-phase high-performance liquid chromatography (HPLC) and further characterised by Tricine SDS-PAGE and Q-TOF ESI MS. Antibacterial activity of bacteriocin was assessed against 16 different Gram-positive and Gram-negative bacterial strains, and their effect on morphology was observed under scanning electron microscopy (SEM). Biofilm adherence and inhibition were evaluated by crystal violet assay, fluorescence microscopy and SEM. RESULTS AND CONCLUSIONS: Bacteriocin preparation exhibited broad-spectrum activity against both Gram-positive and Gram-negative bacteria, and SEM analysis revealed membrane pore formation. On treating with various enzymes, bacteriocin was found to be sensitive to proteases, which confirmed its proteinaceous nature. Bacteriocin showed its applicability at acidic pH in the urinary tract. Antibiofilm activity of bacteriocin established its significance in catheter-associated biofilm inhibition against Pseudomonas aeruginosa and Staphylococcus aureus. Molecular weight of bacteriocins, namely Bac F1 and Bac F2 as resolved by RP-HPLC, was estimated to be 4039 Da and 1609 Da, respectively.