Abstract
Multidrug-resistant (MDR) pathogenic bacteria are hazardous and ongoing threats worldwide, which urges searching for novel bioeffectual alternatives for combating MDR attacks. Herein, it was targeted to extract chitosan (Cht) from fungal culture (Mucor circinelloides) and transform it to nanochitosan (NCht), to biosynthesize selenium nanoparticles (SeNPs) directly using Hibiscus sabdariffa extract (HbE), and to conjugate these bioactive agents and assess their biocidal actions against MDR bacterial pathogens (Klebsiella pneumoniae, Salmonella typhimurium, and Staphylococcus aureus). The fungal Cht had 86.71% deacetylation and transformed effectually to NCht with a 67.6 nm average particle diameter. The SeNPs were innovatively and simply biosynthesized by direct interaction with HbE, which were validated visually, calorimetrically, and biochemically; the HbE/SeNPs had a 12.1 nm mean size. The conjugation between NCht and HbE/SeNPs was proven via structural and biochemical analysis. The entire fabricated NPs/nanocomposites exhibited elevated bactericidal actions toward all MDR pathogens; NCht/HbE/SeNPs were the most powerful with the widest growth inhibition zones and minimal bactericidal concentrations. The most sensitive bacteria were K. pneumoniae, whereas S. aureus displayed the utmost resistance. The ultrastructure of treated K. pneumoniae with NCht/HbE/SeNPs evidenced the attachment of nanocomposite particles to bacterial membranes and the full bacterial lysis/death within 8 h of exposure. The compositing of NCht with HbE-biosynthesized SeNPs provided powerful ideal bactericidal conjugates against MDR pathogens with warranted biosafety, eco-friendliness, and effectuality.