Novel erythromycin lipid nanoformulations for aquaculture applications

AIMS: This study introduces novel lipid nanoformulations of erythromycin (ERY) designed for aquaculture pathogens and evaluates their in vitro antimicrobial activity compared to pure ERY. METHODS AND RESULTS: Among the tested formulations, the nanoemulsion (F4) demonstrated higher inhibitory effects. The MIC values were 25 µg ml-1 against Aeromonas hydrophila and Aeromonas caviae, and for Aeromonas veronii, all ERY-loaded nanoformulations displayed high activity (MIC ≤ 3.1 µg ml-1), as determined by the broth microdilution method. Lipid nanoformulations were prepared using a hot emulsification method. The method consisted of high-speed homogenization at 22 000 rpm for 5 min using an Ultra-Turrax homogenizer, followed by ultrasonication. The surfactants used included poloxamer and natural surfactants, quillaja (Quillaja saponaria Molina) saponins, and whey protein concentrate. The nanoformulations were characterized by particle size (228-500 nm), polydispersity (0.189-0.456), zeta potential (-42--27.5 mV), pH (4.54-5.5), conductivity (161-295 µS cm-1), and stability. CONCLUSIONS: The nanoemulsion (F4) kept higher ERY content at early time points and showed equal or lower MICs than free ERY against selected Aeromonas spp. The dispersions can be spray-dried to a powder or incorporated into fish feed by extrusion or post-pellet coating-routes rarely reported for ERY in aquaculture. These results support further development of ERY nanoformulations against aquaculture pathogens.