ABSTRACT

The poultry industry has been facing the impact of necrotic enteritis (NE), a disease caused by the bacterium Clostridium perfringens producing the haemolytic toxin NetB. NE severity may vary from mild clinical to prominent enteric signs causing reduced growth rates and affecting feed conversion ratio. NetB production is controlled by the Agr-like quorum-sensing (QS) system, which coordinates virulence gene expression in response to bacterial cell density. In this study, the peptide-containing cell-free spent media (CFSM) from Enterococcus faecium was tested in NE challenged broilers in two battery cage and one floor pen studies. Results showed a significant reduction of NE mortality. Metagenomic sequencing of the jejunum microbiome revealed no impact of the CFSM on the microbial community, and growth of C. perfringens was unaffected by CFSM in vitro. The expression of QS-controlled virulence genes netB, plc and pfoA was found to be significantly repressed by CFSM during the mid-logarithmic stage of C. perfringens growth and this corresponded with a significant decrease in haemolytic activity. Purified fractions of CFSM containing bioactive peptides were found to cause reduced haemolysis. These results showed that bioactive peptides reduce NE mortality in broilers by interfering with the QS system of C. perfringens and reducing bacterial virulence. Furthermore, the microbiome of C. perfringens-challenged broilers is not affected by quorum sensing inhibitor containing CFSM.

摘要

家禽业一直面临坏死性肠炎（NE）的影响，这是一种由产气荚膜梭菌产生溶血毒素 NetB 引起的疾病。NE 的严重程度可能有所不同，从轻微的临床症状到明显的肠道症状，导致生长速度降低并影响饲料转化率。NetB 的产生由类似 Agr 的群体感应 (QS) 系统控制，该系统根据细菌细胞密度协调毒力基因表达。在这项研究中，来自屎肠球菌的含肽无细胞废培养基 (CFSM)在两个笼式笼和一个地板栏研究中在 NE 挑战的肉鸡中进行了测试。结果显示 NE 死亡率显着降低。空肠微生物组的宏基因组测序显示 CFSM 对微生物群落没有影响，产气荚膜梭菌的生长在体外也不受 CFSM 的影响。发现 QS 控制的毒力基因netB、plc和pfoA的表达在产气荚膜梭菌生长的对数中期阶段被 CFSM 显着抑制，这与溶血活性的显着降低相对应。研究发现含有生物活性肽的 CFSM 纯化组分可减少溶血。这些结果表明，生物活性肽通过干扰产气荚膜梭菌的QS系统并降低细菌毒力来降低肉鸡的NE死亡率。此外，受产气荚膜梭菌攻击的肉鸡的微生物群不受含有CFSM的群体感应抑制剂的影响。