The effect of probiotic Enterococcus gallinarum L-1 on the innate immune parameters of outstanding species to marine aquaculture

Abstract

In this work, we evaluated the effect of the probiotic Enterococcus gallinarum L-1 on the cellular immune system of four different fish species of great interest in aquaculture such as gilthead sea bream (Sparus aurata), European sea bass (Dicentrarchus labrax), meagre (Argyrosomus regius) and red porgy (Pagrus pagrus). Phagocytic activity, respiratory burst and peroxidase content of leucocytes were observed 30 minutes after incubation with the probiotic E. gallinarum strain L-1, alive or inactivated with heat shock or ultraviolet (UV) light at different concentrations of 10⁷, 10⁸ and 10⁹ cfu mL⁻¹ (final concentration 10⁶, 10⁷ and 10⁸ cfu mL⁻¹). E. gallinarum produced dose-dependent increments in respiratory burst in red porgy, sea bream and sea bass leucocytes. About 10⁶ and 10⁷ cfu mL⁻¹ of live and inactivated bacteria with no stimulation of the respiratory burst activity of sea bream and red porgy head kidney leucocytes was shown. The highest values of peroxidase content were observed in red porgy cells with stimulation indexes higher than 1 in each treatment. Statistical analysis revealed that differences were only significant in sea bream where UV light-inactivated bacteria denote statistically significant differences (P < 0.05) with respect to other treatments. Highest values of phagocytic activity were obtained in sea bream leucocytes incubated with live bacteria (26% ± 1.88), where significant differences (P < 0.05) with other species were detected. Our results suggest that the in vitro assays may be useful in optimising their effective dose and viability for the immunomodulatory effects of probiotic bacteria, although in vivo studies are necessary to confirm the immunomodulatory effect of this strain.

Keywords:

• probiotic
• gilthead sea bream
• European sea bass
• meagre
• red porgy

Acknowledgements

Lorena Román was recipient of Ph.D. grant by Cabildo Insular de Gran Canaria. The authors wish to thank CANEXMAR SL and Instituto Canario de Ciencias marinas (ICCM) for providing the fish for this research.

Additional information

Funding

This research was supported by a grant from the Canary Islands Government, Spain [PI2007/047; EXMAR] and FEDER, European Union.