Antibacterial properties and in silico modeling perspective of nano ZnO transported oxytetracycline-Zn2+ complex [ZnOTc]+ against oxytetracycline-resistant Aeromonas hydrophila

Emergence of antibiotics resistance has threatening consequences not only for human health but also for animal health issues in agriculture. Several animal pathogenic bacteria have developed antibiotic resistance and managing same has tremendous cost repercussions and may lead to total harvest loss. Hence in the present study, efforts are made to revitalize an old antibiotic molecule, oxytetracycline (OTc), through nanodelivery approaches using zinc oxide nanoparticles (nZnO) to confront OTc resistant fish pathogenic bacteria Aeromonas hydrophila. OTc was impregnated in nZnO through in situ precipitation method to develop OTc loaded ZnO nanoparticles (OTc@nZnO) with average size of 99.42 nm. Spectroscopic investigation of same revealed complexation of Zn with amide and aromatic carbonyl moieties of OTc [ZnOTc]. The complex performed better against A. hydrophila with 7-15 mm inhibition zone as compared to nil for bare OTc at same dose. OTc also showed MIC of 150 µg ml and for OTc@nZnO it was 7.02 µg ml with faster killing rate (k, -0.95). In silico docking simulation suggest that [ZnOTc] had low binding affinity (LBE > -5.00 kcal mol) toward TetR(E) and TetA(E) proteins of A. hydrophila as compared to OTc (LBE < -8.00 kcal mol). This study postulates that [ZnOTc] released from OTc@nZnO can escape TetR(E) and TetA(E) resistance proteins and bind at 30S ribosomal subunit with high affinity (<-11.00 kcal mol) to exert antibacterial properties. In the recent scenario of recurrent antimicrobial resistance, the develop antibiotic-nanocomposites could come out as potential solution, however further study is required for its feasibility for use in animal health care.