Plasmid curing and antibiotic resistance reversal in multidrug-resistant <i>Escherichia coli</i> using silver nanoparticles and SDS

Background. The gram-negative bacterium known as Escherichia coli is one of the most prevalent types of bacteria that are responsible for opportunistic infections, especially in clinical settings. As a result of the proliferation of multidrug-resistant (MDR) E. coli bacteria, which represent a substantial risk to public health, many traditional antibiotics are no longer effective against them. On account of this growing resistance, there is an immediate and pressing need to investigate alternate treatment approaches. This study aimed to characterize plasmid profiles associated with antibiotic resistance in E. coli isolates from clinical specimens and evaluate the effectiveness of silver nanoparticles (AgNPs) and sodium dodecyl sulfate (SDS) in plasmid curing and reversing antibiotic resistance. Materials and methods. Multidrug resistance was assessed using the agar disk diffusion method by measuring the inhibition zones around antibiotic-impregnated disks. Plasmids were extracted and analyzed via agarose gel electrophoresis to identify resistance-associated genetic elements. Plasmid curing was performed using 10% SDS, AgNPs, and a combination of both agents. Antibiotic susceptibility was retested post-curing to assess any changes in resistance. Results. Among the tested E. coli isolates, 75% showed resistance to tetracycline, erythromycin, and chloramphenicol. Plasmid profiling confirmed the presence of resistance-carrying plasmids in these strains. Following plasmid curing, previously resistant isolates demonstrated restored sensitivity to the antibiotics, confirming the plasmid-mediated nature of resistance. Isolates lacking plasmid bands remained sensitive throughout. Notably, AgNPs alone showed significant antibacterial activity, especially against gram-negative bacteria such as E. coli, which may be attributed to the structural differences in the bacterial cell wall and the presence of fimbriae that enhance nanoparticle uptake. Conclusion. This study highlights the potential of silver nanoparticles, alone or in combination with SDS, as promising agents for plasmid curing and reversing antibiotic resistance in multidrug-resistant E. coli. The findings provide insight into the mechanism by which nanoparticles interact with bacterial cells and offer a foundation for future development of novel antibacterial therapies.