Antimicrobial Efficacy of Oil-in-Water Nanoemulsion Against Vibrio fluvialis and Vibrio mimicus

The study focuses on assessing the antimicrobial properties of a nanoemulsion against Vibrio spp., including Vibrio fluvialis and Vibrio mimicus, which are known to cause diseases in aquaculture. It has been periodically inducing gastroenteritis by transmitting various diseases to humans and causing illness. The castor and olive oil nanoemulsions (CA-NE and OL-NE) were prepared using micro-fluidization techniques and characterized by DLS to determine the size, zeta potential, and polydispersity index. The effectiveness of the nanoemulsion was evaluated against pathogenic Vibrio spp. by preliminary tests such as minimum inhibitory concentration and minimum bactericidal concentration using the microdilution method. Additional tests included adherence, antibiofilm assays, live/dead staining, and oxygen consumption rate (OCR) studies. The anti-adherence efficacy for OL-NE was 45.33% against V. fluvialis, whereas gentamicin exhibited an inhibition rate of 29.27%. In the biofilm assay, OL-NE showed higher inhibition, achieving rates of 45.89%, against V. fluvialis. The live/dead staining results indicated that OL-NE caused a significant percentage of dead cells (54.72%) against the V. mimicus, comparable to the current antibiotic gentamicin (54.87%). The oxygraph analysis measured the oxygen consumption rate (OCR) of CA-NE showed a reduction of 0.67, while the current antibiotics exhibited a 0.89-fold reduction against V. fluvialis. This indicates that CA-NE had a better reduction rate (0.22-fold) than the current antibiotics compared to untreated (1.0). Thus, nanoemulsions have better results observed with adherence, biofilm, and OCR rate against V. fluvialis, whereas live/dead results are better against V. mimicus. Notably, in all cases, NEs surpassed the performance of the current antibiotics and exhibited a successful inhibition rate.