Piperine exhibits promising antibiofilm activity against Staphylococcus aureus by accumulating reactive oxygen species (ROS).

Staphylococcus aureus causes numerous community-acquired and nosocomial infections in humans by exploiting biofilm. In this context, this study aims to impede the formation of Staphylococcus aureus biofilm by exposing the cells to a plant-based alkaloid, piperine. Our study revealed that piperine exhibited considerable antimicrobial activity against the test organism. However, we had tested the lower concentrations (up to 32 µg/mL) of piperine to observe whether they could show any antibiofilm activity against the same organism. Several experiments, like crystal violet (CV) assay, estimation of total biofilm protein, and fluorescence microscopic observations, established that lower concentrations (up to 16 µg/mL) of piperine showed efficient antibiofilm activity against Staphylococcus aureus. In this connection, we also noticed that the lower concentrations (8 and 16 µg/mL) of piperine showed a considerable reduction in microbial metabolic activity. Besides, it was also observed that the mentioned concentrations of piperine did not compromise the microbial growth of the target organism while exhibiting antibiofilm activity. To understand the underlying mechanism of microbial biofilm inhibition under the influence of piperine, we observed that the compound was found to accumulate reactive oxygen species in the bacterial cells that could play an important role in the inhibition of biofilm formation. Furthermore, the tested concentrations (8 and 16 µg/mL) of piperine were able to inhibit the motility of the test organism that might compromise the development of biofilm. Thus, piperine could be considered as a potential agent for the effective management of biofilm threat caused by Staphylococcus aureus.

Tryptophan interferes with the quorum sensing and cell surface hydrophobicity of Staphylococcus aureus: a promising approach to inhibit the biofilm development.

Staphylococcus aureus, a Gram-positive bacterium has been implicated in a plethora of human infections by virtue of its biofilm-forming ability. Inhibition in microbial biofilm formation has been found to be a promising approach towards compromising microbial pathogenesis. In this regard, various natural and synthetic molecules have been explored to attenuate microbial biofilm. In this study, the role of an amino acid, L-tryptophan was examined against the biofilm-forming ability of S. aureus. The compound did not execute any antimicrobial characteristics, instead, showed strong antibiofilm activity with the highest biofilm inhibition at a concentration of 50 µg/mL. Towards understanding the underlying mechanism of the same, efforts were given to examine whether tryptophan could inhibit biofilm formation by interfering with the quorum-sensing property of S. aureus. A molecular docking analysis revealed an efficient binding between the quorum-sensing protein, AgrA, and tryptophan. Moreover, the expression of the quorum-sensing gene (agrA) got significantly reduced under the influence of the test compound. These results indicated that tryptophan could interfere with the quorum-sensing property of the organism thereby inhibiting its biofilm formation. Further study revealed that tryptophan could also reduce the cell surface hydrophobicity of S. aureus by downregulating the expression of dltA. Moreover, the tested concentrations of tryptophan did not show any significant cytotoxicity. Hence, tryptophan could be recommended as a potential antibiofilm agent to manage the biofilm-associated infections caused by S. aureus. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s13205-021-02924-3.

1,4-Naphthoquinone accumulates reactive oxygen species in Staphylococcus aureus: a promising approach towards effective management of biofilm threat.

Staphylococcus aureus, a Gram-positive opportunistic microorganism, promotes pathogenicity in the human host through biofilm formation. Microorganisms associated with biofilm often exhibit drug-resistance property that poses a major threat to public healthcare. Thus, the exploration of new therapeutic approaches is the need of the hour to manage biofilm-borne infections. In the present study, efforts are put together to test the antimicrobial as well as antibiofilm activity of 1,4-naphthoquinone against Staphylococcus aureus. The result showed that the minimum bactericidal concentration (MBC) of this compound was found to be 100 µg/mL against Staphylococcus aureus. In this regard, an array of experiments (crystal violet, biofilm protein measurement, and microscopic analysis) related to biofilm assay were conducted with the sub-MBC concentrations (1/20 and 1/10 MBC) of 1,4-naphthoquinone. All the results of biofilm assay demonstrated that these tested concentrations (1/20 and 1/10 MBC) of the compound (1,4-naphthoquinone) showed a significant reduction in biofilm development by Staphylococcus aureus. Moreover, the tested concentrations (1/20 and 1/10 MBC) of the compound (1,4-naphthoquinone) were able to reduce the microbial motility of Staphylococcus aureus that might affect the development of biofilm. Further studies revealed that the treatment of 1,4-naphthoquinone to the organism was found to increase the cellular accumulation of reactive oxygen species (ROS) that resulted in the inhibition of biofilm formation by Staphylococcus aureus. Hence, it can be concluded that 1,4-naphthoquinone might be considered as a promising compound towards biofilm inhibition caused by Staphylococcus aureus.