Molecular identification of an invasive gingival bacterial community

On the Oral Microbiome of Oral Potentially Malignant and Malignant Disorders: Dysbiosis, Loss of Diversity, and Pathogens Enrichment

The role of dysbiosis in the development and progression of oral potentially malignant disorders (OPMDs) remains largely unknown. Here, we aim to characterize and compare the oral microbiome of homogeneous leucoplakia (HL), proliferative verrucous leukoplakia (PVL), oral squamous cell carcinoma (OSCC), and OSCC preceded by PVL (PVL-OSCC). Fifty oral biopsies from HL (n = 9), PVL (n = 12), OSCC (n = 10), PVL-OSCC (n = 8), and healthy (n = 11) donors were obtained. The sequence of the V3-V4 region of the 16S rRNA gene was used to analyze the composition and diversity of bacterial populations. In the cancer patients, the number of observed amplicon sequence variants (ASVs) was lower and Fusobacteriota constituted more than 30% of the microbiome. PVL and PVL-OSCC patients had a higher abundance of Campilobacterota and lower Proteobacteria than any other group analyzed. A penalized regression was performed to determine which species were able to distinguish groups. HL is enriched in Streptococcus parasanguinis, Streptococcus salivarius, Fusobacterium periodonticum, Prevotella histicola, Porphyromonas pasteri, and Megasphaera micronuciformis; PVL is enriched in Prevotella salivae, Campylobacter concisus, Dialister pneumosintes, and Schaalia odontolytica; OSCC is enriched in Capnocytophaga leadbetteri, Capnocytophaga sputigena, Capnocytophaga gingivalis, Campylobacter showae, Metamycoplasma salivarium, and Prevotella nanceiensis; and PVL-OSCC is enriched in Lachnospiraceae bacterium, Selenomonas sputigena, and Prevotella shahii. There is differential dysbiosis in patients suffering from OPMDs and cancer. To the best of our knowledge, this is the first study comparing the oral microbiome alterations in these groups; thus, additional studies are needed.

Characteristics of Oral Microbiota in Patients with Esophageal Cancer in China

Gut microbiota dysbiosis is closely associated with intestinal carcinogenesis, but the oral microbiota of patients with esophageal squamous cell carcinoma who live in high-risk regions in China has not been fully characterized. In the current study, oral microbial diversity was investigated in 33 patients with esophageal squamous cell carcinoma and 35 healthy controls in Chongqing, China, by sequencing 16S rRNA of V3-V4 gene regions. There were statistically significant differences in oral microbiota between esophageal squamous cell carcinoma patients and controls as determined via unweighted pair-group analysis with arithmetic means. At the phylum level, in esophageal squamous cell carcinoma patients, there were comparatively greater amounts of Firmicutes (34.0% vs. 31.1%) and Bacteroidetes (25.3% vs. 24.9%) and lower amounts of Proteobacteria (17.0% vs. 20.1%). At the genus level, esophageal squamous cell carcinoma patients exhibited comparatively greater amounts of Streptococcus (17.3% vs. 14.5%) and Prevotella_7 (8.6% vs. 8.5%) and lower amounts of Neisseria (8.1% vs. 10.7%). Using a linear discriminant analysis effect size method, Planctomycetes and Verrucomicrobia were identified in the esophageal squamous cell carcinoma group. 10 genera were higher abundances identified in the healthy control group, and different 10 genera were identified in the esophageal squamous cell carcinoma group. In the present study, there were significant differences in oral microbial compositions of esophageal squamous cell carcinoma patients and healthy controls. Further longitudinal and mechanistic studies are needed to further characterize relationships between oral microbiota and esophageal squamous cell carcinoma.

Impact of microbiota in colorectal carcinogenesis: lessons from experimental models

A role of gut microbiota in colorectal cancer (CRC) growth was first suggested in germ-free rats almost 50 years ago, and the existence of disease-associated bacteria (termed pathobionts) had becoming increasingly evident from experimental data of fecal transplantation, and microbial gavage or monoassociation. Altered bacterial compositions in fecal and mucosal specimens were observed in CRC patients compared to healthy subjects. Microbial fluctuations were found at various cancer stages; an increase of bacterial diversity was noted in the adenoma specimens, while a reduction of bacterial richness was documented in CRC samples. The bacterial species enriched in the human cancerous tissues included Escherichia coli, Fusobacterium nucleatum, and enterotoxigenic Bacteroides fragilis. The causal relationship of gut bacteria in tumorigenesis was established by introducing particular bacterial strains in in situ mouse CRC models. Detailed experimental protocols of bacterial gavage and the advantages and caveats of different experimental models are summarized in this review. The microbial genotoxins, enterotoxins, and virulence factors implicated in the mechanisms of bacteria-driven tumorigenesis are described. In conclusion, intestinal microbiota is involved in colon tumorigenesis. Bacteria-targeting intervention would be the next challenge for CRC.

Sequence-specific DNA solid-phase extraction in an on-chip monolith: Towards detection of antibiotic resistance genes

Antibiotic resistance of bacteria is a growing problem and presents a challenge for prompt treatment in patients with sepsis. Currently used methods rely on culturing or amplification; however, these steps are either time consuming or suffer from interference issues. A microfluidic device was made from black polypropylene, with a monolithic column modified with a capture oligonucleotide for sequence selective solid-phase extraction of a complementary target from a lysate sample. Porous properties of the monolith allow flow and hybridization of a target complementary to the probe immobilized on the column surface. Good flow-through properties enable extraction of a 100μL sample and elution of target DNA in 12min total time. Using a fluorescently labeled target oligonucleotide related to Verona Integron-Mediated Metallo-β-lactamase it was possible to extract and detect a 1pM sample with 83% recovery. Temperature-mediated elution by heating above the duplex melting point provides a clean extract without any agents that interfere with base pairing, allowing various labeling methods or further downstream processing of the eluent. Further integration of this extraction module with a system for isolation and lysis of bacteria from blood, as well as combining with single-molecule detection should allow rapid determination of antibiotic resistance.

Mucositis and oral infections secondary to gram negative rods in patients with prolonged neutropenia

Patients with prolonged neutropenia are at risk for a variety of complications and infections including the development of mucositis and oral ulcers. The changes in oral flora during chemotherapy and its effects on the development of infections of the oral cavity have been studied with inconsistent results. However, there is evidence that supports the colonization of gram negative rods in patients undergoing chemotherapy. In this report, we present two leukemic patients who developed oral ulcers secondary to multi-drug resistant Pseudomonas aeruginosa. It is important to suspect multi-drug resistant gram negative rods in patients with prolonged neutropenia who develop gum infections despite appropriate antibiotic coverage.

Identification of bacterial pathogens from formalin-fixed, paraffin-embedded tissues by using 16S sequencing: retrospective correlation of results to clinicians' responses

16S sequencing on formalin-fixed, paraffin-embedded (FFPE) material has been used to identify bacteria when culture-based phenotyping techniques have not worked. The objective of this study was to determine how frequently 16S sequencing used in FFPE material was helpful to clinicians in the diagnosis and treatment of infectious diseases. Requests for testing occurred upon consultation between an infectious disease pathologist and a surgical pathologist or an infectious disease physician. A selected paraffin block from each case was referred for 16S sequencing. Retrospectively, we correlated clinical history and management decisions on 27 cases that were tested by paneubacterial 16S sequencing. Samples included 24 surgical specimens, 1 autopsy, and 2 cytology blocks. Seventeen (63%) of the 27 cases had a positive 16S sequencing. Acute inflammation was present in 10 of these cases, and organisms were observed using special stains in 3. In 11 (65%) of the 17 cases, clinicians considered the organism identified by 16S sequencing to be the cause or possible cause of the infectious process. Organisms included common (Citrobacter) and fastidious bacteria (Haemophilus, Fusobacterium). In 3 cases, clinicians changed antibiotic treatment based on the bacteria identified, whereas in 8 (including 2 where no organism was found), clinicians continued the antibiotic treatment. The use of 16S sequencing on FFPE identified specific bacteria even when organisms were not observed histopathologically. 16S results had an impact in infectious disease management decisions.

Reconstitution and structure of a bacterial Pnkp1-Rnl-Hen1 RNA repair complex

Ribotoxins cleave essential RNAs for cell killing, and RNA repair neutralizes the damage inflicted by ribotoxins for cell survival. Here we report a new bacterial RNA repair complex that performs RNA repair linked to immunity. This new RNA repair complex is a 270-kDa heterohexamer composed of three proteins-Pnkp1, Rnl and Hen1-that are required to repair ribotoxin-cleaved RNA in vitro. The crystal structure of the complex reveals the molecular architecture of the heterohexamer as two rhomboid-shaped ring structures of Pnkp1-Rnl-Hen1 heterotrimer fused at the Pnkp1 dimer interface. The four active sites required for RNA repair are located on the inner rim of each ring. The architecture and the locations of the active sites of the Pnkp1-Rnl-Hen1 heterohexamer suggest an ordered series of repair reactions at the broken RNA ends that confer immunity to recurrent damage.

Anaerobic ferrous oxidation by heterotrophic denitrifying enriched culture

Heterotrophic denitrifying enriched culture (DEC) from a lab-scale high-rate denitrifying reactor was discovered to perform nitrate-dependent anaerobic ferrous oxidation (NAFO). The DEC was systematically investigated to reveal their denitrification activity, their NAFO activity, and the predominant microbial population. The DEC was capable of heterotrophic denitrification with methanol as the electron donor, and autotrophic denitrification with ferrous salt as the electron donor named NAFO. The conversion ratios of ferrous-Fe and nitrate-N were 87.41 and 98.74 %, and the consumption Fe/N ratio was 2.3:1 (mol/mol). The maximum reaction velocity and half saturation constant of Fe were 412.54 mg/(l h) and 8,276.44 mg/l, and the counterparts of N were 20.87 mg/(l h) and 322.58 mg/l, respectively. The predominant bacteria were Hyphomicrobium, Thauera, and Flavobacterium, and the predominant archaea were Methanomethylovorans, Methanohalophilus, and Methanolobus. The discovery of NAFO by heterotrophic DEC is significant for the development of wastewater treatment and the biogeochemical iron cycle and nitrogen cycle.

Invasive potential of gut mucosa-derived Fusobacterium nucleatum positively correlates with IBD status of the host

BACKGROUND

Fusobacterium nucleatum is a heterogeneous oral pathogen that is also a common resident of the human gut mucosa. Given that some strains of F. nucleatum are known to be invasive and proinflammatory in the oral mucosa, we compared strains isolated from patients with inflammatory bowel disease (IBD) with strains isolated from healthy controls to determine 1) whether this species was more commonly associated with IBD patients; and 2) whether gut-derived F. nucleatum strains from IBD patients showed an increased capacity for invasion.

METHODS

Biopsy material was obtained from 56 adult patients undergoing colonoscopy for colon cancer screening purposes or assessment of irritable bowel syndrome status (34 patients), or to assess for presence of gastrointestinal disease (i.e., IBD or indeterminate colitis, 22 patients). We enumerated Fusobacterium spp. strains isolated from human gut biopsy material in a blinded fashion, and then compared the virulence potential of a subset of F. nucleatum strains using an invasion assay in a Caco-2 model system.

RESULTS

Fusobacterium spp. were isolated from 63.6% of patients with gastrointestinal disease compared to 26.5% of healthy controls (P = 0.01). In total, 69% of all Fusobacterium spp. recovered from patients were identified as F. nucleatum. F. nucleatum strains originating from inflamed biopsy tissue from IBD patients were significantly more invasive in a Caco-2 cell invasion assay than strains that were isolated from healthy tissue from either IBD patients or control patients (P < 0.05 to 0.001).

CONCLUSIONS

This study indicates that colonization of the intestinal mucosa by highly invasive strains of F. nucleatum may be a useful biomarker for gastrointestinal disease.

Leptotrichia species in human infections

Leptotrichia species typically colonize the oral cavity and genitourinary tract. These anaerobic bacteria belong to the normal flora of humans and are seldom found in clinically significant specimens. However, on rare occasions, Leptotrichia has been isolated from blood cultures of patients with lesions in the oral mucosa, in particular from patients with neutropenia. These organisms should be considered potential pathogens in neutropenic patients, especially when breaks in the mucosal barriers are present through which they frequently spread to the bloodstream. Leptotrichia has also been recovered from immunocompetent persons, e.g. patients with endocarditis. Although their role in infections remains elusive and not much is known, they have been suggested as emerging pathogens. The present review deals with taxonomy, diagnosis, clinical importance, pathogenesis, host defence, infection control, and spectrum of Leptotrichia infections, and ends with a few typical case reports. Currently, six species have been validly published, but a number of yet uncultivable species exist. Molecular methods recovering uncultivable species should be used to get a real idea of their role as pathogens.

Advances in nucleic acid-based diagnostics of bacterial infections

Methods for rapid detection of infectious bacteria and antimicrobial-resistant pathogens have evolved significantly over the last decade. Many of the new procedures are nucleic acid-based and replace conventional diagnostic methods like culturing which is time consuming especially with fastidious and slow growing microorganisms. The widespread use of antibiotics has resulted in an increased number of cases with resistant microorganisms such as methicillin-resistant Staphylococcus aureus, vancomycin resistant enterococci, and multidrug-resistant Mycobacterium tuberculosis. Rapid detection of these pathogens is important to isolate patients and prevent further spreading of the diseases. Newly developed diagnostic procedures are superior with respect to turnaround time, sensitivity and specificity. Methods like multiplex real time PCR and different array-based technologies offer the possibility of multiparameter assays where several pathogens and antibiotic resistance genes can be detected simultaneously.