Enhanced nanoencapsulation of gentamicin, ciprofloxacin, and lysozyme in chitosan-MIL-53 metal–organic frameworks for a synergistic activity against drug-resistant Salmonella from poultry and human origins

Abstract

The escalating crisis of antimicrobial resistance (AMR), particularly in foodborne pathogens like non-typhoidal Salmonella, necessitates innovative therapeutic strategies. This study first characterized multidrug-resistant (MDR) Salmonella serovars isolated from poultry and clinical sources in Egypt, confirming high resistance rates to gentamicin and ciprofloxacin, mediated by *aadA-2* and qnrA genes. To overcome this challenge, we engineered a novel, multi-agent nano-delivery system designed for synergy and controlled release. A Quality-by-Design (QbD) approach using a Box–Behnken design optimized the formulation of chitosan-based nanoparticles encapsulating gentamicin, ciprofloxacin, lysozyme, and MIL-53(Fe) metal–organic frameworks (MOFs). Molecular docking analysis supported the dual antibacterial and anti-virulence potential of the system, showing strong binding of its components to the Salmonella SipD invasion protein. The optimized hybrid nanoformulation exhibited favorable characteristics: a particle size of 248 ± 11 nm, a positive zeta potential (+33.8 mV), and efficient encapsulation of all agents. It demonstrated superior in vitro antibacterial efficacy against MDR Salmonella isolates, evidenced by the largest inhibition zone (19.33 ± 1.76 mm), the lowest minimum inhibitory concentration (MIC) (2.93 ± 0.73 µg mL⁻¹) and minimum bactericidal concentration (MBC) (4.40 ± 2.20 µg mL⁻¹) values, and a fractional inhibitory concentration index (FICI) of 0.15, confirming strong synergy. Crucially, the formulation provided sustained release over 72 hours, fitting the Higuchi diffusion model, in stark contrast to the rapid release of free drugs. The novelty of this work lies in the rational design and statistical optimization of a chitosan-MOF hybrid system for the synergistic co-delivery of two antibiotics with a membrane-disrupting enzyme, creating a potent, sustained-release weapon against MDR Salmonella. This platform promises enhanced therapeutic efficacy, reduced dosing frequency, and a potential decrease in resistance development.