Bilophila wadsworthia is a non-spore-forming, obligate anaerobic, gram-negative rod that occurs a commensal in the gut microbiome. This bacterial species is known as an opportunistic pathogen, as it has been frequently isolated from patients with perforated appendicitis, gangrenous appendicitis [1], and various infections such as polymicrobial sepsis or abscesses [2,3].

Bilophila wadsworthia causes western diet-driven inflammatory and metabolic diseases. The predominantly consumed high-fat diet (HFD) increases the abundance of B. wadsworthia in the human gut [4]. Additionally, the colonization by B. wadsworthia induces a T helper type 1 (Th1) immune response through dendritic cells (DCs), leading to colitis in vivo [5]. Long-term colonization by B. wadsworthia aggravates HFD-induced metabolic dysfunctions, such as increased glucose dysmetabolism and hepatic steatosis in mice [6]. However, the precise causative mechanisms remain unclear.

Pathogen-associated molecular patterns (PAMPs), such as lipopolysaccharide (LPS), lipoprotein, CpG DNA, ribosomal RNA, and flagellin, are released from bacteria and stimulate the host innate immune response [7,8]. Mosca et al. [9] showed that LPS produced by B. wadsworthia can cause inflammation. Although their study suggested the involvement of other PAMPs derived from B. wadsworthia in causing or worsening inflammation in the gut, it is unclear which specific PAMP causes the response.

In the present study, we performed whole-genome sequencing (WGS) analysis of 25 B. wadsworthia isolates to identify the virulence factor genes. We then focused on the PAMP-producing genes. Based on the results of genomic sequence analysis, we conducted in vitro immune assay and in vivo study to determine whether the selected virulence factors contributed to inflammation.