Characterization of intratissue bacterial communities and isolation of Escherichia coli from oral lichen planus lesions

Abstract

Oral lichen planus (OLP) is a chronic T cell-mediated inflammatory disease of unknown etiology. We previously proposed that the intracellular bacteria detected in oLp lesions are important triggering factors for T cell infiltration. This study aimed to identify OLP-associated bacterial species through the characterization of intratissue bacterial communities of OLP lesions. Seven pairs of bacterial communities collected from the mucosal surface and biopsied tissues of oLp lesions were analyzed by high-throughput sequencing of the 16S rRNA gene. The intratissue bacterial communities were characterized by decreased alpha diversity but increased beta diversity compared with those on the mucosal surface. While the relative abundance of most taxa was decreased within the tissues, that of Escherichia coli was significantly increased. Four E. coli strains were isolated from additional OLP biopsies and verified as K12 strains by whole-genome sequencing. The distribution of E. coli in sections of control (n = 12) and OLP (n = 22) tissues was examined by in situ hybridization. E. coli was detected in most OLP tissues, suggesting its potential role in the pathogenesis of OLP. The oral E. coli strains isolated from oLp tissues will be useful to investigate their role as triggering factors for t cell infiltration. Oral lichen planus (OLP) is a T cell-mediated chronic mucocutaneous disease of unknown etiology and is currently incurable. OLP occurs in 0.5-4% of the global population and appears more prevalent in females than males at a ratio of 1.5:1 1-3. The main histological features of OLP include band-like lymphocytic infiltration at the superficial part of connective tissue, the presence of liquefaction degeneration in the basal cell layer and the absence of epithelial dysplasia 4. Although the etiology and pathogenesis of OLP are not completely understood, unknown antigens are thought to trigger T cell infiltration and inflammatory responses of infiltrated lymphocytes such as CD4 + and CD8 + T cells 5. What triggers the activation and recruitment of T cells is an important question to find new therapeutics for OLP. Recently, many researchers have attempted to understand the relationship between human diseases and the human microbiome through high-throughput sequencing technology. To date, four research groups have studied the oral microbiota associated with OLP by sequencing the 16S rRNA gene, and differences in the microbiota of saliva and buccal mucosa between healthy controls and OLP patients have been reported 2,6-9. We previously reported increased bacterial invasion into the lamina propria, the presence of bacteria within basal epithelial cells and T cells in OLP lesions, and the induction of T cell chemokines by oral bacteria 6. In addition, Mizuki et al. reported that Mycoplasma salivarium was detected by immunohistochemistry in the epithelium and lymphocyte infiltrate area in 58.5% of OLP tissues from Japanese patients 10. These results suggest that oral bacteria may have a role in the pathogenesis of OLP. Howeve...

Association of a dysbiotic oral microbiota with the development of focal lymphocytic sialadenitis in IκB-ζ-deficient mice

“…E. coli is a common gut commensal of humans and mice, although there are diverse pathogenic strains that can cause diseases in the intestinal or urinary tracts 29 . E. coli has also been detected in the oral cavity of humans and mice, and oral strains have been recently isolated from the biopsy tissues of oral lichen planus patients 30 , 31 . E. gallinarum , which was enriched in Nfkbiz −/− mice, is known to translocate from the gut to the liver and induce autoantibodies in (NZW × BXSB)F1 mice, an autoimmune-prone strain.…”

Genomic characterization of fourEscherichia colistrains isolated from oral lichen planus biopsies

“…Although S. flexneri is considered a different entity from E. coli in clinical disease, S. flexneri and E. coli genetically constitute the same species [ 27 ]. In a previously reported phylogenetic tree, the OLP-isolated E. coli strains were more closely related to S. flexneri 2457 T than to E. coli Nissle 1917 [ 11 ].…”

“…The patient 7 was a 60-year-old female and had reticular, erythematous, and ulcerative lesions at one, three, and one areas, respectively. While the biopsy of the patient 5 presented acanthosis and band-shaped infiltrate only in some areas, that of the patient 7 showed atrophy and heavy infiltrate in all areas, in addition to the liquefaction degeneration of the epithelial basal layer which was a common feature [11]. We generated 6.71 Gbp of Illumina MiSeq shortread data, which resulted in 166-195x coverage per strain (Table 1).…”

“…We recently reported a significant enrichment of Escherichia coli in the intratissue bacterial communities of OLP lesions and isolated four E. coli strains from OLP biopsies. Furthermore, strong signals of E. coli were detected in most OLP tissues [ 11 ]. Although E. coli colonizing the human intestine is mostly commensal, there are diverse pathogenic strains that cause enteric diseases, urinary tract infections, and sepsis/meningitis [ 12 ].…”

“…It is currently unclear whether the E. coli strains isolated from OLP tissues are oral commensals, pathobionts, or pathogens because our attempts to isolate E. coli from buccal swabs of healthy subjects have failed, despite the presence of E. coli in the buccal microbiota of the subjects [ 10 , 11 ]. Pathogenic E. coli strains usually acquire pathogenicity through horizontal gene transfer of virulence factors encoded on transposons, plasmids, bacteriophages, or pathogenicity islands and through deletions or point mutations of regulatory genes [ 12 ].…”