Isolation, screening, and anti-infectious evaluation of Enterococcus faecium capable of inducing trained immunity

Abstract:

[Background] The innate immune system is the first defense line and plays a key role in the host defense against microbial early infection. Enhancing the innate immunity from trained immunity is an effective way to improve the resistance of animals to diseases. [Objective] To isolate the bacteria capable of inducing trained immunity from healthy porcine intestinal flora and thus provide new insights for the prevention and control of microbial diseases by trained immunity. [Methods] Bacteria were isolated from healthy pig feces, and the strains capable of inducing trained immunity were screened with Galleria mellonella, a well-established model. The strain screened out was identified by 16S rRNA gene sequencing and characterized by growth curve. Its capability of inducing trained immunity was then evaluated in a mouse model. [Results] A strain SC-2 capable of inducing trained immunity in G. mellonella was identified as Enterococcus faecium. Administration of SC-2 significantly increased the percentages of neutrophils and macrophages in the peripheral blood and lung, decreased the bacteria loads in main organs, and increased the survival rate of mice infected by Streptococcus suis. [Conclusion] SC-2 had the effect of inducing trained immunity in mice. Our study provides new insights for immune regulation and disease treatment from the perspective of trained immunity.

Key words:Enterococcus faecium;trained immunity;Galleria mellonella;isolation and identification