This study introduces the bioformulations of Ag/BBR and ZnO/BBR complexes against pathogenic bacteria in the gastrointestinal tract. Without the use of toxic reduction agents, Ag and ZnO NPs were prepared using an electrochemical method and then facially mixed with BBR solution to form Ag/BBR and ZnO/BBR complexes. BBR molecules are strongly conjugated with Ag and ZnO NPs through coordinated bonding and electrostatic interaction. As a result, the presence of BBR significantly influenced the nanoparticle growth, resulting in the formation of core/shell structured Ag/BBR and ZnO/BBR NPs with small particle sizes. The antibacterial test showed that BBR, Ag, or ZnO components all contributed to the increase of antibacterial ability of Ag/BBR and ZnO/BBR NPs against both methicillin-resistant Staphylococcus aureus (MRSA) and Salmonella enteritidis (S. enteritidis). The bactericidal ability of Ag/BBR and ZnO/BBR complexes against MRSA was exhibited even at a concentration of four-fold dilution (corresponding to 1.25 g L⁻¹ of BBR and 46.25 mg L⁻¹ of Ag) and two-fold dilution (corresponding to 2.5 g L⁻¹ of BBR and 10 mg L⁻¹ of ZnO), respectively, while that of the Ag/BBR complex against S. enteritidis showed at a concentration of two-fold dilution corresponding to 2.5 g L⁻¹ of BBR and 92.5 mg L⁻¹ of Ag. The results obtained in this study support that Ag/BBR and ZnO/BBR complexes can be potential therapeutic agents against gastrointestinal infections.