Gut Lactococcus garvieae promotes protective immunity to foodborne Clostridium perfringens infection.

The gut microbiota, a pivotal component of the intestinal mucosal barrier, is critical for host resistance to enteric pathogen infection. Here, we report a novel function of the potentially probiotic Lactococcus garvieae strain LG1 (L. garvieae strain LG1) in maintaining intestinal mucosal barrier integrity and protecting against foodborne Clostridium perfringens (C. perfringens) infection. L. garvieae was isolated from the intestinal contents of Chinese Mongolian sheep (MS) and exhibited potential probiotic properties. In a C. perfringens enterocolitis model, L. garvieae-pretreated mice were less susceptible to C. perfringens infection compared with Phosphate buffered solution (PBS)-pretreated mice, which manifested as higher survival rates, lower pathogen loads, less weight loss, mild clinical symptoms and intestinal damage, and minor inflammation. Further mechanistic analysis showed that L. garvieae could ameliorate the disruption of intestinal permeability and maintain the integrity of the intestinal mucosal barrier by promoting the expression of tight junction proteins and mucoproteins. Moreover, L. garvieae was also able to facilitate antimicrobial peptide expression and ameliorate dysbiosis of the gut microbiota caused by C. perfringens. Together, these findings highlight the prospect of immunomodulatory potentially probiotic L. garvieae and might offer valuable strategies for prophylaxis and/or treatment of pathogenic C. perfringens mucosal infection. IMPORTANCE: C. perfringens necrotic enteritis leads to losses of about US $2 billion to the poultry industry worldwide every year. Worse, US Centers for Disease Control and Prevention (CDC) has estimated that C. perfringens causes nearly 1 million foodborne illnesses in the United States annually. Nowadays, the treatment recommendation is a combination of a broad-spectrum synergistic penicillin with clindamycin or a carbapenem, despite growing scientific concern over antibiotic resistance. The global understanding of the gut microbiome for C. perfringens infection may provide important insights into the intervention. L. garvieae originated from Mongolian sheep intestine, exhibited potentially probiotic properties, and was able to limit C. perfringens enterocolitis and pathogenic colonization. Importantly, we found that L. garvieae limits C. perfringens invasion via improving intestinal mucosal barrier function. Also, L. garvieae alleviates C. perfringens-induced gut microbiota dysbiosis. It allowed us to convince that utilization of probiotics to promote protective immunity against pathogens infection is of pivotal importance.

Phagocyte extracellular traps formation contributes to host defense against Clostridium perfringens infection.

Clostridium perfringens (C. perfringens) is an important Gram-positive anaerobic spore-forming pathogen that provokes life-threatening gas gangrene and acute enterotoxaemia, although it colonizes as a component of the symbiotic bacteria in humans and animals. However, the mechanisms by which C. perfringens is cleared from the host remains poorly understood, thereby impeding the development of novel strategies for control this infection. Here, we uncover a beneficial effect of extracellular traps (ETs) formation on bacterial killing and clearance by phagocytes. C. perfringens strain ATCC13124, and wild-type isolates CP1 and CP3 markedly trigger ETs formation in macrophages and neutrophils. As expected, visualization of DNA decorated with histone, myeloperoxidase (MPO) and neutrophils elastase (NE) in C. perfringens-triggered classical ETs structures. Notably, the bacteria-induced ETs formation is an ERK1/2-, P38 MAPK-, store-operated calcium entry (SOCE)-, NADPH oxidase-, histone-, NE-, and MPO-dependent process, and is independent of LDH activity. Meanwhile, the defect of bactericidal activity is mediated by impairing ETs formation in phagocytes. Moreover, In vivo studies indicated that degradation of ETs by DNase I administration leads to a defect in the protection against experimental gas gangrene, with higher mortality rates, exacerbated tissue damage, and more bacterial colonization. Together, these results suggest that phagocyte ETs formation is essential for the host defense against C. perfringens infection.

Erratum: Mixed lineage kinase-like protein protects against Clostridium perfringens infection by enhancing NLRP3 inflammasome-extracellular traps axis.

[This corrects the article DOI: 10.1016/j.isci.2022.105121.].

Mixed lineage kinase-like protein protects against Clostridium perfringens infection by enhancing NLRP3 inflammasome-extracellular traps axis.

Despite intense research in understanding Clostridium perfringens (C. perfringens) pathogenesis, the mechanisms by which it is cleared from the host are largely unclarified. In C. perfringens gas gangrene and enterocolitis model, Mlkl -/- mice, lacking mixed lineage kinase-like protein (MLKL), are more susceptible to C. perfringens infection. Mlkl deficiency results in a defect in inflammasome activation, and IL-18 and IL-1ß releases. Exogenous administration of recombinant IL-18 is able to rescue the susceptibility of Mlkl -/- mice. Notably, K+ efflux-dependent NLRP3 inflammasome signaling downstream of active MLKL promotes bacterial killing and clearance. Interestingly, the defect of bactericidal activity is also mediated by decreased classical extracellular trap formation in the absence of Mlkl. Our results demonstrate that MLKL mediates extracellular trap formation in a NLRP3 inflammasome-dependent manner. These findings highlight the requirement of MLKL for host defense against C. perfringens infection through enhancing NLRP3 inflammasome-extracellular traps axis.