Plasmid-mediated multidrug resistance and the antibacterial potential of plant seed proteins

Abstract

The rapid emergence of multidrug-resistant (MDR) bacteria, largely driven by excessive and indiscriminate antibiotic use, poses a critical threat to global health. Conventional antibiotics are increasingly ineffective against resistant pathogens, particularly those harboring plasmid-mediated resistance mechanisms. The purpose of this study is to assess the antibacterial efficacy of chickpea-derived seed proteins (7S, 11S globulins, and bioactive seed fractions) as natural alternative treatments, and to determine the prevalence of MDR among clinical bacterial isolates. We hypothesized that chickpea seed proteins, particularly the basic subunit (BS) fraction, would exhibit significant antibacterial efficacy against MDR strains, including those harboring plasmid-mediated resistance. Ten clinical bacterial isolates were subjected to antibiotic susceptibility testing using the Kirby–Bauer disc diffusion method. Resistant strains were further analyzed through plasmid profiling, curing experiments, and agarose gel electrophoresis to distinguish plasmid-mediated from chromosomal resistance. Antibacterial proteins were isolated from chickpea seeds, including 7S and 11S globulins, along with a BS fraction. Their antibacterial activity was assessed against resistant isolates. Using scanning electron microscopy (SEM) and transmission electron microscopy (TEM), morphological and structural alterations brought on by protein treatment were investigated, offering insights into bacterial adaptability and protein-mediated inhibition. Antibiotic susceptibility testing revealed widespread resistance, with cephalexin and clindamycin showing the lowest effectiveness (80–90% resistance). Klebsiella oxytoca and Proteus mirabilis exhibited complete resistance (Multi antibiotics resistant [MAR] = 1.0), underscoring their clinical significance. Plasmid profiling demonstrated that 13 of 21 resistant isolates carried plasmids, confirming plasmid-mediated resistance to β-lactam and phenicol antibiotics, while others exhibited chromosomal resistance. TEM and SEM analyses revealed that resistant Klebsiella oxytoca and Bacillus subtilis maintained intact morphology despite high antibiotic exposure, suggesting mutation-driven adaptation. Chickpea-derived protein fractions displayed notable antibacterial activity, with the BS fraction exerting the strongest inhibition, particularly against K. oxytoca and P. mirabilis . This study highlights the alarming prevalence of plasmid- and mutation-mediated antibiotic resistance among clinical isolates. Chickpea proteins, especially the BS fraction, demonstrated significant antibacterial activity against MDR pathogens, offering a promising natural alternative to conventional antibiotics. Their ability to inhibit resistant strains suggests potential applications in therapeutic development and infection control.