Enhanced antibacterial activity of amoxicillin combination with a Cu-Fe sulfide mineral against antimicrobial-resistant bacteria.

Abstract

Antibiotic resistance (AMR) poses a significant global threat to public health and necessitates the development of new strategies to improve antibiotic efficacy. In the present study, Swarn Makshik (SM) Bhasma (CuFeS₂) was synthesised and loaded with amoxicillin (AMX) to form an SM-AMX complex aimed at combating AMR bacterial strains. The physicochemical properties of synthesized SM-AMX were analysed by using UV-Vis, XRD, FTIR, SEM-EDS, DLS and Zeta potential. The loading efficiency of SM-AMX was 72.67 ± 3.31%. The incorporation of AMX into SM was confirmed by XRD and FTIR analyses, while FE-SEM imaging, EDS spectra and elemental mapping further verified the formation of SM-AMX composite. The average hydrodynamic particle size of SM was 554.2 nm, with a zeta potential of -7.7 mV, indicating heterogeneous particle distribution and limited colloidal stability. The antimicrobial activity of SM-AMX was evaluated against Staphylococcus aureus, Escherichia coli, and AMR strains including Shigella flexneri, and Enterobacter hormaechei. The SM-AMX formulation exhibited a higher zone of inhibition compared to SM and AMX alone. Additionally, the MIC values were 31.25 µg/mL for E. coli, 15.625 µg/mL for S. aureus, 31.25 µg/mL for S. flexneri, and 15.625 µg/mL for E. hormaechei. The time kill assay results further demonstrated that SM enhances the AMX antimicrobial efficacy by decreasing the cell count during the incubation period against treated bacterial strains. Cytotoxicity assessment in Caco-2 cells revealed acceptable biocompatibility, with cell viability remaining above 75% at the highest tested concentration (500 µg/mL). This study provides a promising and sustainable strategy for enhancing efficacy against AMR bacterial strains.