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 A. caviae, and for A. 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 minutes 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 to -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.