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 (IC₅₀) of 7.96±3.05 µg mL¹ (n = 6) at 24 hrs incubation. Lupinifolin at the concentrations of sub-MICs (1, 2, 4 and 8 µg mL¹) 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 mL¹) and vancomycin (1 µg mL¹) 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.

Synergistic Activity of Lupinifolin in Combinations with Antibiotics Against Staphylococcus aureus.

<b>Background and Objective:</b> Antibacterial resistance is one of the top global public health problems. The use of natural substances, which can enhance the antibacterial activity of currently used medications, is a promising alternative to oppose antibacterial resistance. The pharmacological activities of lupinifolin, a prenylated flavanone isolated from stems of <i>Derris reticulata</i> Craib., against growth and biofilm formation of <i>Streptococcus mutans</i> and <i>Staphylococcus aureus</i> have been previously documented. Nonetheless, interactions between lupinifolin and other antibacterial agents have not been determined. This study aimed to investigate the effects of lupinifolin in combinations with some antibacterial agents, specifically ampicillin, cloxacillin or vancomycin, against <i>S. mutans</i>, Methicillin-Sensitive <i>S. aureus</i> (MSSA) and Methicillin-Resistant <i>S. aureus</i> (MRSA). <b>Materials and Methods:</b> The checkerboard assay was performed to determine the antibacterial activity of lupinifolin plus the testing antibacterial agents. The Fractional Inhibitory Concentration Index (FICI) was calculated to indicate the interaction between lupinifolin and the antibacterial agent tested. <b>Results:</b> Lupinifolin exerted the synergistic activity when using in combination with ampicillin or cloxacillin against MSSA with the FICIs of <u><</u>0.5. The potential synergistic effect was also observed with lupinifolin plus ampicillin or cloxacillin against MRSA. However, the combination of lupinifolin plus vancomycin resulted in no interaction against MRSA. The combined effects of lupinifolin and ampicillin or cloxacillin against <i>S. mutans</i> were somewhat ambiguous with the borderline values of FICI of 0.5156 and 0.5625, respectively. <b>Conclusion:</b> Lupinifolin potentially plays a role as an antibacterial intensifier against some pathogenic gram-positive bacteria, particularly MSSA and MRSA. Nonetheless, further experiments are required to explain the precise mechanism of synergy.

Anticariogenic Activities of Derris reticulata Ethanolic Stem Extract Against Streptococcus mutans.

BACKGROUND AND OBJECTIVE: Streptococcus mutans is a dominant causative pathogen of dental caries, which is a major oral health problem affecting million people worldwide. Derris reticulata is a medicinal plant possessing antimicrobial activity against several Gram-positive pathogenic bacteria. None the less, its effects on growth and cariogenic properties of S. mutans has not been clearly established. This study aimed to investigate the antibacterial and anti cariogenic activities of the D. reticulata ethanolic stem extract. MATERIALS AND METHODS: The TLC analysis was performed to authenticate the D. reticulata sample. Minimum inhibition concentration and minimum bactericidal concentration were determined by using broth dilution and drop plate methods, respectively. Sucrose dependent and sucrose independent-adherences, biofilm formation and glycolytic pH drop assays were performed to evaluate the anticariogenic activity. RESULTS: The ethanolic stem extract of D. reticulata possessed the antibacterial activity against S. mutans with the MIC and MBC of 0.875±0.250 and 1.750±0.500 mg mL-1, respectively. The extract at the lower concentrations of sub-MIC also had significant inhibitory actions against the cariogenic properties of S. mutans, including surface adherence, biofilm formation and glycolytic acid production. CONCLUSION: The D. reticulata stem extract had a substantial anticariogenic activities and thus potentially be developed as an oral health care product for dental caries prevention in the near future.