Chitosan and polyacrylic acid engineered AlFeO₃ validated degradation of rhodamine B and resistant Pseudomonas aeruginosa of epizootic ulcerative syndrome in Ctenopharyngodon idella with mechanistic insights

Fish epizootic ulcerative syndrome (EUS) caused by resistant strains of Pseudomonas aeruginosa (P. aeruginosa) presents a significant challenge. The present research objective was to synthesize dual biopolymer engineered aluminium ferrite (AlFeO₃) nanostructures (NSs) doped with polyacrylic acid (PAA), as stabilizing agent, and chitosan, bioactive dopant, (CS/PAA-AlFeO₃) to address the catalytic reduction of rhodamine B (RhB) dye and resistance challenge in Ctenopharyngodon idella (Grass carp) affected by EUS as not previously reported for AlFeO₃ based systems. The maximum catalytic degradation rates towards RhB in basic and neutral media were 76.1% and 82.7% for PAA-AlFeO₃, respectively. For antibacterial assessment, the impeded tissues from the gills and pancreas of clinically affected Grass carp, averaging 120 ± 2 g in weight and 20 ± 3 cm in length, were retrieved and inoculated into nutrient broth following overnight incubation. The susceptibility of unique isolates to specific antibiotics was assessed using the disc diffusion method on Mueller-Hinton agar. The in-vitro antibacterial potential of the synthesized CS/PAA-AlFeO₃ NSs was assessed at concentrations of 500 μg/50 μL and 1000 μg/50 μL against resistant P. aeruginosa utilizing the agar well diffusion method. The synthesized 4 wt% CS/PAA-AlFeO₃ NSs demonstrated significant (P < 0.05) bactericidal efficacy, with an inhibition zone of 5.15 ± 0.02 mm against resistant P. aeruginosa. Molecular docking elucidated the bactericidal mechanism of CS/PAA-AlFeO₃ by emphasizing their inhibitory effect on DNA gyrase in P. aeruginosa. The outcomes suggested that synthesized NSs are promising candidates, warranting further investigations to manage resistant bacterial infections in aquaculture and to reduce RhB.