Isolation of porcine intestinal Lactobacillus salivarius and antimicrobial potential of its biosurfactant

Background Lactobacillus salivarius ( L. salivarius ) is a probiotic widely colonized in the gastrointestinal tracts of humans and animals. Its biosurfactant (BS) exhibits antibacterial and antiviral activities, along with advantages such as biodegradability, non-toxicity, and stability. Porcine circovirus type 2 (PCV2) is a major pathogen in swine farms, causing immunosuppression or immune dysfunction. Elevated susceptibility in PCV2-positive herds is accompanied by severe secondary bacterial infections. To explore novel antimicrobial biologics for enhancing swine immunity, this study isolated a biosurfactant-producing Lactobacillus strain from the intestines of PCV2-infected piglets using the calcium carbonate plate method, and analyzed the anti-microbial activity of the biosurfactant. Results A strain of biosurfactant-producing L. salivarius was successfully isolated from the ileum of PCV2-infected piglets. The extracted BS from the isolate demonstrated surface tension-reducing properties, forming spreading zones or dispersions on vegetable oil. The antimicrobial experiment showed that at the concentrations of 6.25–50 mg/mL, BS inhibited the growth of porcine E. coli and S. suis by 46.13% − 95.06% and 46.13% − 95.06%, respectively. Furthermore, BS of 6.25–12.5 mg/mL significantly inhibited PCV2 replication in PK-15 cells. These findings suggest that L. salivarius is a promising probiotic candidate for improving swine immune status and developing novel alternatives to conventional antimicrobial agents.