New Insights into the Antimicrobial Potential of Polyalthia longifolia—Antibiofilm Activity and Synergistic Effect in Combination with Penicillin against Staphylococcus aureus

Abstract

Widespread antibiotic resistance has led to the urgent need for the identification of new antimicrobials. Plants are considered a valuable potential resource for new effective antimicrobial compounds. Therefore, in the present study, we focused on the antimicrobial activity of Polyalthia longifolia plants harvested from Cameroon using the minimum inhibitory concentration (MIC), minimum bactericidal concentration (MBC), and time-kill assays. The mechanism of action was investigated by employing fluorescence and scanning electron microscopy. The anti-Staphylococcus aureus activity was studied using biofilm inhibition and checkerboard assays. Our results revealed that the tested extracts possess important antimicrobial activities, notably against Gram positive bacteria (MICs as low as 0.039 mg/mL). P. longifolia leaf extracts exhibited a significant bactericidal effect, with a total kill effect recorded after only 2 h of exposure at concentrations equivalent to MBC (0.078 and 0.156 mg/mL). The extracts showed a synergistic antibacterial activity in combination with penicillin against a MRSA clinical isolate and significantly inhibited S. aureus biofilm formation. The mechanism of action is related to the impairment of cell membrane integrity and cell lysis. All these findings suggest that P. longifolia could be an important source of reliable compounds used to develop new antimicrobials.

Staphylococcus aureus biofilm: Formulation, regulatory, and emerging natural products-derived therapeutics

“…Moreover, the tested components revealed that high-level suppression of biofilm formation (62–76 %) at their MICs, which could potentiate the antibacterial effects of each other at their sub-inhibitory concentrations (1/2∼1/16 MIC) in the synergistic cocktails by increasing the penetration of compounds into the matrix of biofilm [ 134 ]. Likewise, Polyalthia longifolia leaf extracts showed a synergistic action with penicillin against a clinical MRSA isolate and significantly inhibited the biofilm formation, implying their combinational antibiofilm potential [ 135 ]. Sannat et al explicitly reported that the methanolic extract of Hemidesmus indicus root synergized the antibiofilm activity of amoxicillin and clindamycin against MRSA isolates.…”

Application of Rosmarinic Acid with Its Derivatives in the Treatment of Microbial Pathogens

“…RA has a bacteriostatic effect, capable of destroying bacterial cells and their proteins as well as blocking Na+/K+-ATPase activity in the cell [ 189 ]. In addition, rosmarinic acid specifically inhibits the P-protein of hepatitis B virus [ 218 ], RA could influence the early state of viral infection and directly affect viral particles by affecting virus-P-selectin glycoprotein ligand-1 (PSGL1) interactions with heparan sulfate substance without affecting virus–scavenger receptor B2 (SCARB2) interactions [ 196 ].…”