Isolation of Enterococcus faecium with Feeding Attractant Function from Pacific White Shrimp (Litopenaeus vannamei) Intestine

Abstract

In the present study, we isolated the lactic acid bacterium strain SC-01 from Pacific white shrimp (Litopenaeus vannamei) intestine. Using conventional and molecular methods, we identified the bacterium as Enterococcus faecium, and found it had the function of feeding attractant and could inhibit the development of Vibrioparahaemolyticus (zone of inhibition: 14mm). The attractant effect of its fermentation broth is significantly better than that of the chemical attractant trimethylamine oxide (TMAO) (P <0.05), and is equivalent to that of dimethyl-beta-propiothetin (DMPT) based on the feeding behavior of shrimp. High performance liquid chromatography (HPLC) analysis suggested that inosine-5’-monophosphate (IMP) may be a component of the attractant. A biosecurity evaluation revealed a negative result in hemolytic assays, and no shrimp mortality was resulted from SC-01 fermentation broth challenge. Feeding trials (60 days) indicated that the SC-01 fermentation broth (viable counts: 5.7×109 cfumL−1) could improve feed intake, weight gain rate (WGR) and specific growth rate (SGR), and decrease the count of Vibrio sp. in the intestine of shrimp.