Receptor-targeted Lactococcus lactis mitigate Clostridium difficile infection

Engineered bacteria play an important role in colorectal disease. Lactococcus lactis (L. lactis) can inhibit Clostridium difficile (C. difficile) by producing antimicrobial peptide nisin. However, its insufficient nisin production levels, lack of targeted in vivo release and weak colonization ability may limit its therapeutic efficacy against C. difficile infection (CDI). In this study, we engineered a strain of L. lactis with high adherence and therapeutic potential (Lla+) by expressing C. difficile adhesion protein Cwp8 on the surface of a L. lactis strain with high nisin yield (4,019 to 4,028 IU/mL). The adhesion effect of Lla+ was increased by 1.3-fold compared to the wild type L. lactis in the HT-29 cell model. We created the lipid membrane-coated L. lactis (LCL) by encapsulating Lla+ with the ROS-responsive lipid membrane. LCL exhibited targeted release of nisin payload in response to H2O2, lipopolysaccharide and C. difficile in vitro, as well as in various mouse models of intestinal inflammation in vivo. The therapeutic effect of LCL against CDI was substantial, reducing C. difficile survival by 60% compared to the untreated control. In the treatment of recurrent CDI (rCDI), LCL outperformed the drug fidaxomicin, the first-line treatment for rCDI recommended by Infectious Diseases Society of America (IDSA), decreasing C. difficile survival by 48% and lowering the levels of toxins TcdA and TcdB by 57.1% and 65%, respectively. These results suggested that the presented the encapsulation approach could serve as a delivery platform to target inflamed intestines and expand the application of probiotics as pharmaceuticals.