EFFICACY OF GREEN SYNTHESISED ZINC OXIDE NANOPARTICLES AGAINST MULTI-DRUG RESISTANT NON- TYPHOIDAL SALMONELLA SPP.
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Date
2022-04-02
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COLLEGE OF VETERINARY AND ANIMAL SCIENCES POOKODE, LAKKIDI
Abstract
In the recent wake of antimicrobial resistance, nanotechnology has received
remarkable attention and has been considered as a promising interventional tool for
treating the drug resistant pathogens. The present study evaluated the antibacterial
efficacy of green synthesised Zinc Oxide nanoparticles (ZnO NPs) against multi-drug
resistant non-typhoidal Salmonella spp. (MDR-NTS). The synthesis and
characterisation of ZnO NPs was attempted using the aqueous extract of Piper longum
catkin. Initially, the characterisation of green synthesised ZnO NPs was performed by
UV- Vis spectroscopy, Fourier transform infra- red spectroscopy (FTIR),
Thermogravimetric analysis (TGA) and differential thermogravimetric analysis
(DTA), powder X-ray diffraction (PXRD), Scanning electron microscopy (SEM) and
Transmission electron microscopy (TEM). The green synthesised ZnO NPs exhibited
an absorbance peak at 340 nm by UV- Vis spectroscopy, which was confirmed by FTIR
analysis. The TGA/DTA revealed a progressive thermal degradation of the ZnO NPs
between 250oC and 400oC, however, a good thermal stability was exhibited for
annealing temperatures between 900oC and 1300oC. The ZnO NPs exhibited a
hexagonal wurtzite crystalline structure by PXRD analysis, which was further
confirmed by SEM and TEM. This study evaluated the in vitro antibacterial efficacy
of ZnO NPs against MDR- NTS strains (S. enterica Typhimurium and S. Enteritidis
(n= 3 for each serotype). The minimum inhibitory concentration (MIC; 125 μg/ml) and
minimum bactericidal concentration (MBC; 250 μg/ml) of ZnO NPs was determined
by employing microbroth dilution technique. Later, ZnO NPs was also tested for its
stability (high- end temperatures, physiological concentration of cationic salts,
proteases and pH); safety (chicken RBCs; HEK cell lines) and effect on gut beneficial
lactobacilli (Lactobacillus acidophilus and L. plantarum). In general, the ZnO NPs
tested stable at MIC concentration; however, a three to four- fold rise in the MBC value
was observed. Besides, ZnO NPs were tested safe with chicken RBCs and HEK cell lines at MIC (1X, 2X, 5X and 10X) levels; moreover, the beneficial gut lactobacilli
were not inhibited. Furthermore, the in vitro time- kill kinetic assay of MDR-NTS
strains treated with ZnO NPs revealed a complete clearance after 360 min. To conclude,
the biosynthesised ZnO NPs was found to exhibit antibacterial activity against the
tested MDR-NTS, found stable and safe. Overall, the study demonstrated facile, eco-
friendly method for the synthesis of ZnO NPs, which could be employed as a potential
antimicrobial alternative candidate.
Description
Submitted in partial fulfilment of the requirement for the degree of
Master of Veterinary Science in Veterinary Public Health