Antibiofilm Formation Activity of Lupinifolin Against Methicillin-Resistant Staphylococcus aureus.

<b>Background and Objective:</b> Biofilm formation activity of Methicillin-resistant <i>Staphylococcus aureus</i> (MRSA) is one of the crucial factors rendering this pathogenic bacterium difficult to be eradicated. It has been reported that lupinifolin, is a major phytochemical agent isolated from <i>Derris reticulata</i> Craib. stem possesses antibacterial activity against MRSA. This study aimed to investigate the effects of lupinifolin and its combinations with some antibacterial drugs, including ampicillin, cloxacillin or vancomycin, on the biofilm formation activity of MRSA. <b>Materials and Methods:</b> The crystal violet biofilm formation assay was performed to evaluate the biofilm formation activity. <b>Results:</b> Lupinifolin produced a significant inhibitory activity against MRSA biofilm formation with the median inhibitory concentration (IC<sub>50</sub>) of 7.96±3.05 μg mL<sup>1</sup> (n = 6) at 24 hrs incubation. Lupinifolin at the concentrations of sub-MICs (1, 2, 4 and 8 μg mL<sup>1</sup>) combined with the antibacterial drugs at their sub-MICs also exhibited substantial antibiofilm formation activities. The maximal antibiofilm activity was found with the combination of lupinifolin (8 μg mL<sup>1</sup>) and vancomycin (1 μg mL<sup>1</sup>) by the percentage inhibition of 102.39±0.89 (n = 8). The antibiofilm formation activities of the combinations between lupinifolin and the antibacterial drugs at various concentrations tested were also significantly higher than those of lupinifolin alone. <b>Conclusion:</b> These results indicated that lupinifolin can potentially be developed as an antibacterial enhancer for the management of biofilm-associated bacterial infections caused by MRSA, in which the current pharmacological treatment is still limited.