Characterization and Evaluation of Layered Bi2WO6 Nanosheets as a New Antibacterial Agent

Background: Pathogenic microorganisms are causing increasing cases of mortality and morbidity, along with alarming rates of ineffectiveness as a result of acquired antimicrobial resistance. Bi2WO6 showed good potential to be used as an antibacterial substance when exposed to visible light. This study demonstrates for the first time the dimension-dependent antibacterial activity of layered Bi2WO6 nanosheets. Materials and methods: The synthesized layered Bi2WO6 nanosheets were prepared by the hydrothermal method and characterized by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM), and Raman and Fourier transform infrared spectroscopy (FTIR). Antibacterial and antibiotic-modulation activities were performed in triplicate by the microdilution method associated with visible light irradiation (LEDs). Results: Bi2WO6 nanosheets were effective against all types of bacteria tested, with MIC values of 256 μg/mL against Escherichia coli standard and resistant strains, and 256 μg/mL and 32 μg/mL against Staphylococcus aureus standard and resistant strains, respectively. Two-dimensional (2D) Bi2WO6 nanosheets showed antibacterial efficiency against both strains studied without the presence of light. Conclusions: Layered Bi2WO6 nanosheets revealed dimension-dependent antibacterial activity of the Bi2WO6 system

Antibacterial Activity of the Essential Oil of <i>Piper tuberculatum</i> Jacq. Fruits against Multidrug-Resistant Strains: Inhibition of Efflux Pumps and β-Lactamase

Antimicrobial resistance has become a growing public health concern in recent decades, demanding a search for new effective treatments. Therefore, this study aimed to elucidate the phytochemical composition and evaluate the antibacterial activity of the essential oil obtained from the fruits of Piper tuberculatum Jacq. (EOPT) against strains carrying different mechanisms of antibiotic resistance. Phytochemical analysis was performed using gas chromatography–mass spectrometry (GC/MS). The antibacterial activity of EOPT and its ability to inhibit antibiotic resistance was evaluated through the broth microdilution method. The GC-MS analysis identified 99.59% of the constituents, with β-pinene (31.51%), α-pinene (28.38%), and β-cis-ocimene (20.22%) being identified as major constituents. The minimum inhibitory concentration (MIC) of EOPT was determined to assess its antibacterial activity against multidrug-resistant strains of Staphylococcus aureus (IS-58, 1199B, K2068, and K4100). The compound showed a MIC of ≥ 1024 μg/mL, suggesting a lack of intrinsic antibacterial activity. However, when the EOPT was associated with antibiotics and EtBr, a significant decrease in antibiotic resistance was observed, indicating the modulation of efflux pump activity. This evidence was corroborated with the observation of increased fluorescent light emission by the bacterial strains, indicating the involvement of the NorA and MepA efflux pumps. Additionally, the significant potentiation of ampicillin activity against the S. aureus strain K4414 suggests the β-lactamase inhibitory activity of EOPT. These results suggest that the essential oil from P. tuberculatum fruits has antibiotic-enhancing properties, with a mechanism involving the inhibition of efflux pumps and β-lactamase in MDR S. aureus strains. These findings provide new perspectives on the potential use of EOPT against antibiotic resistance and highlight the importance of Piper species as sources of bioactive compounds with promising therapeutic activities against MDR bacteria. Nevertheless, further preclinical (in vivo) studies remain necessary to confirm these in vitro-observed results