Screening of Bacteriocin-producing Enterococcus faecalis Strains for Antagonistic Activities against Clostridium perfringens.

This study was conducted to isolate and characterize bacteriocin-producing bacteria against Clostridium perfringens (C. perfringens) from domestic animals to determine their usefulness as probiotics. Bacteriocin-producing bacteria were isolated from pig feces by the spot-on-lawn method. A total of 1,370 bacterial stains were isolated, and six were tentatively selected after identifying the inhibitory activity against the pathogenic indicator C. perfringens KCTC 3269 and KCTC 5100. The selected strains were identified as Enterococcus faecalis (E. faecalis) by 16s rRNA sequencing. Most of the isolated bacterial strains were resistant to 0.5% bile salts for 48 h and remained viable after 2 h at pH 3.0. Some E. faecalis also showed strong inhibitory activity against Listeria monocytogenes KCTC 3569, KCTC 3586 and KCTC 3710. In the present study, we finally selected E. faecalis AP 216 and AP 45 strain based on probiotic selection criteria such as antimicrobial activity against C. perfringens and tolerance to acid and bile salts. The bacteriocins of E. faecalis AP 216 and AP 45 strains were highly thermostable, showing anticlostridial activities even after incubation at 121℃ for 15 min. These bacteriocinproducing bacteria and/or bacteriocins could be used in feed manufacturing as probiotics as an alternative to antibiotics in the livestock industry.

Immunomodulatory properties of Enterococcus faecium JWS 833 isolated from duck intestinal tract and suppression of Listeria monocytogenes infection.

The aim of this study was to evaluate the immunomodulatory properties of Enterococcus faecium JWS 833 (JWS 833) isolated from duck intestine and compare them to those of Lactobacillus rhamnosus GG (LGG), a proven immunity-enhancing probiotic. To investigate the immune-enhancing properties of JWS 833, production of nitric oxide (NO) and cytokines was measured in mouse peritoneal macrophages. In addition, a Listeria monocytogenes challenge model was used in the assessment. It was found that heat-killed JWS 833 stimulates mouse peritoneal macrophages to produce NO, interleukin-1 ß (IL-1ß) and tumor necrosis factor-α (TNF-α) and that oral administration of viable JWS833 enhances NO, IL-1ß and TNF-α synthesis upon L. monocytogenes challenge. Moreover, mice fed with JWS 833 were partially protected against lethal challenge with L. monocytogenes. JWS 833 strain has significantly greater immunostimulatory properties than LGG. Moreover, JWS 833 strain partially protects mice against lethal challenge with L. monocytogenes. JWS 833, a novel strain of E. faecium isolated from duck intestine, is potentially a useful feed supplement for controlling pathogens and enhancing host immune responses.