Potential natural antimicrobial and antibiofilm properties of Piper betle L. against Staphylococcus pseudintermedius and methicillin-resistant strains.

ETHNOPHARMACOLOGICAL RELEVANCE: Piper betle L. has potent of antimicrobial activity and is widely used as a traditional remedy to treat skin infections. However, no clear evidence exists concerning antimicrobial and antibiofilm activity against Staphylococcus pseudintermedius and methicillin-resistant S. pseudintermedius (MRSP) opportunistic pathogens that cause wound infections and pyoderma in canines and zoonotic disease. AIM OF THE STUDY: The antimicrobial and antibiofilm activities of P. betle extract were assessed against S. pseudintermedius and MRSP strains. MATERIALS AND METHODS: Ethanol leaf extract of P. betle was investigated for its antibacterial effect on S. pseudintermedius and MRSP by broth microdilution and time-kill assays. Biofilm inhibition and production assays were performed to evaluate antibiofilm and biofilm eradication effects, respectively. Biofilm-associated gene expression was further studied using real-time polymerase chain reaction (PCR). The possible interaction between IcaA and major compounds in P. betle was analyzed by molecular docking. RESULTS: The extract showed minimum inhibitory concentration (MIC) at 250 µg/mL. Growth inhibition of P. betle at 1 MIC against the bacteria was initially observed after treatment for 4 h. All isolates were completely killed after 18 h exposure to the extract. Minimum biofilm inhibitory concentrations (MBICs) of the extract against the tested isolates ranged 1/2 MIC to 1 MIC, while minimum biofilm eradication concentration (MBEC) of P. betle was initialed at 8 MIC. Quantitative inhibition and eradication effects were observed in representative strains. The extract at 1/2 MIC and 1 MIC values inhibited biofilm formation up to 100%, with bacterial biofilm removed at up to 94.21% by 4 MIC of the extract. The extract downregulated the expression of the icaA gene among biofilm-producing isolates. The most abundant compounds, 4-allyl-1,2-diacetoxybenzene and eugenol showed a strong affinity with IcaA protein at -5.65 and -5.31 kcal/mol, respectively. CONCLUSIONS: P. betle extract demonstrated the antibacterial, antibiofilm, and biofilm-removal activity against S. pseudintermedius and MRSP. Downregulation of the icaA gene expression and protein interaction were possible modes of action of the extract that impacted biofilm production. This extract showed promise as an alternative treatment for S. pseudintermedius infection, especially drug-resistant and biofilm-associated cases.

Dual-functional bioactive silk sericin for osteoblast responses and osteomyelitis treatment.

Sericin, a natural protein from silk cocoon, has been reported for various biological properties in the biomaterials field. Modified forms of sericin have been studied for bone tissue engineering, while its unmodified form has been scarcely reported. Therefore, the purpose of this study was to evaluate physical and biological properties of unmodified sericin for potential use in bone surgery. Sericin was extracted from silk cocoons using a chemical-free boiling method. Sericin extract showed distinct bands with molecular weight ranging from 25 to 42 kDa including smear bands. Fourier transform infrared spectra presented characteristic peaks of amide I, II, and III, confirming the chemical composition of sericin. Based on biological activity, sericin extract at a concentration of 40 µg/mL increased the proliferation of osteoblast cells up to 135%, compared with the untreated control. Moreover, increase in antibacterial activity against Staphylococcus aureus, both clinical isolates and the reference strain ATCC 29213, was demonstrated for sericin extract with normal saline, while no antibacterial activity was observed for sericin with broth. It was found that sericin with normal saline showed higher zeta potential than sericin without normal saline, indicating higher system stability. This was confirmed by the average particle size of sericin extract with NaCl (3,249.3±226.1 nm) showing approximately 10 times smaller than sericin solution (29,015.9 ± 8,085.6 nm). Furthermore, sericin extract at the minimal inhibitory concentration significantly reduced the biofilm formation of S. aureus up to 95%. The study indicates biological activities of sericin, which could be applied as a dual-functional bioactive material to support bone regeneration and treat bone infections.