Eco-friendly one-pot synthesis of zinc oxide nanoparticles using catkin extract of Piper longum: In-vitro antibacterial, antioxidant and antibiofilm potential against multi-drug resistant enteroaggregative E. coli

Enteroaggregative Escherichia coli (EAEC) is an emerging bacterial pathogen implicated in gastrointestinal illnesses world-wide and has been documented as one of the foremost causes of acute and persistent diarrhea in children and adults. Of late, an unusual emergence of multi-drug resistance among EAEC strains has been recognized globally; hence the emphasis has been given to adjuvant therapies to combat this nagging public health threat. Nanotechnology has recently received much interest in the wake of antimicrobial resistance (AMR) and is seen to be a promising interventional tool for treating drug-resistant infections. This study assessed the antibacterial efficacy of green synthesized ZnO NPs using aqueous extract of Piper longum catkin against multi-drug resistant strains of enteroaggregative Escherichia coli (MDR-EAEC). Initially, the synthesis of ZnO NPs was confirmed by UV- Vis spectroscopy and Fourier transform infra- red spectroscopy (FTIR) analysis. The TGA/DTA revealed thermal stability of ZnO NPs, while a hexagonal wurtzite crystalline structure was exhibited by PXRD analysis, which was further confirmed by SEM and TEM. The minimum inhibitory concentration as well as minimum bactericidal concentration of bio-fabricated ZnO NPs determined by microbroth dilution technique against MDR-EAEC (n= 3) strains revealed 125 μg/mL and 250 μg/mL, respectively. In addition, ZnO NPs were tested variably stable (high-end temperatures, physiological concentration of salts, proteases and varying pH) and safe (chicken RBCs, HEK cell lines, gut lactobacilli). The green synthesized ZnO NPs exhibited a concentration- dependent antioxidant activity as evidenced by ABTS assay and reducing power assay. Furthermore, the green synthesized ZnO NPs inhibited the biofilm forming ability of the tested MDR-EAEC strains. Overall, this study demonstrated an eco- friendly one-pot synthesis of ZnO NPs, which could be employed as a potential antimicrobial alternative candidate against MDR-EAEC strains.