Binding of Actinobacillus actinomycetemcomitans lipopolysaccharides to Peptostreptococcus micros stimulates tumor necrosis factor alpha production by macrophage-like cells

The role of bacterial infections in rheumatoid arthritis development and novel therapeutic interventions: Focus on oral infections

BACKGROUND

Rheumatoid arthritis (RA) represents a primary public health challenge, which is a major source of pain, disability, and socioeconomic effects worldwide. Several factors contribute to its pathogenesis. Infections are an important concern in RA patients, which play a key role in mortality risk. Despite major advances in the clinical treatment of RA, long-term use of disease-modifying anti-rheumatic drugs can cause serious adverse effects. Therefore, effective strategies for developing novel prevention and RA-modifying therapeutic interventions are sorely needed.

OBJECTIVE

This review investigates the available evidence on the interplay between various bacterial infections, particularly oral infections and RA, and focuses on some potential interventions such as probiotics, photodynamic therapy, nanotechnology, and siRNA that can have therapeutic effects.

A case report of sepsis and death caused by Parvimonas micra, a rare anaerobe

Parvimonas micra is a type of Gram-positive anaerobic cocci widely distributed in the oral cavity, gastrointestinal tract, respiratory tract, and female reproductive system mucosa. It is a conditional pathogen that can cause infections in the human oral cavity, wounds, and other areas as well as sepsis. In this case report, the patient's immune system was compromised by various underlying diseases and a pulmonary infection, which led to the entry of P. micra infection into the bloodstream. P. micra is a slow-growing organism (When a bloodstream infection occurs, flagging an anaerobic bottle of blood culture as positive will usually take >48 h), which makes it hard to secure timely blood culture results. Our patient's poor physical condition eventually led to sepsis, and she died after 5 days in the hospital.

Colorectal Cancer Screening in Inflammatory Bowel Diseases-Can Characterization of GI Microbiome Signatures Enhance Neoplasia Detection?

Current noninvasive methods for colorectal cancer (CRC) screening are not optimized for persons with inflammatory bowel diseases (IBDs), requiring patients to undergo frequent interval screening via colonoscopy. Although colonoscopy-based screening reduces CRC incidence in IBD patients, rates of interval CRC remain relatively high, highlighting the need for more targeted approaches. In recent years, the discovery of disease-specific microbiome signatures for both IBD and CRC has begun to emerge, suggesting that stool-based biomarker detection using metagenomics and other culture-independent technologies may be useful for personalized, early, noninvasive CRC screening in IBD patients. Here we discuss the utility of the stool microbiome as a noninvasive CRC screening tool. Comparing the performance of multiple microbiome-based CRC classifiers, including several multi-cohort meta-analyses, we find that noninvasive detection of colorectal adenomas and carcinomas from microbial biomarkers is an active area of study with promising early results.

Clinical Characteristics of Chronic Lung Abscess Associated with Parvimonas micra Diagnosed Using Metagenomic Next-Generation Sequencing

Purpose

Parvimonas micra (P. micra) is a Gram-positive anaerobic bacterium distributed in the oral cavity, with a potential to become pathogenic causing lung abscess. Due to the lack of specificity of symptoms and the difficulty in culture, the diagnosis of lung abscess associated with P. micra is delayed. It is essential to elucidate the clinical characteristics of lung abscess associated with P. micra.

Methods

From January 2019 to July 2020, five patients with chronic lung abscess associated with P. micra diagnosed by pathological biopsy and metagenomic next-generation sequencing (mNGS) were analyzed in this retrospective study.

Results

Among the five patients, four had a history of smoking, three had periodontitis, and two had a history of drinking. The average course of the disease was 6.5 months. High-density flake-like or mass shadows with irregular boundaries were observed in the chest computed tomography (CT) images of the five patients, and liquefactive necrosis was detected in the middle of the lesions; however, no gas-liquid plane or cavity was noted, making it difficult to distinguish a lung cancer. The pathological biopsy of the five patients showed chronic inflammation of lung tissue, and P. micra was detected by mNGS in the biopsy or bronchoalveolar lavage fluid samples. Two patients were treated with amoxicillin-clavulanate, two had metronidazole, and one had moxifloxacin. Among them, four recovered after receiving antibiotic treatment, and the remaining one underwent surgical resection due to poor antibiotic treatment effect.

Conclusion

Chronic lung abscess associated with P. micra, common in elderly male smokers with poor oral hygiene, is often diagnosed in a delayed manner and misdiagnosed as lung cancer. The mNGS technology is beneficial to the rapid determination of P. micra.

Quantification of Fusobacterium nucleatum at Depths of Root Dentinal Tubules in the Tooth Using Real-time Polymerase Chain Reaction: An In Vitro Study

INTRODUCTION

Microorganisms have been known to cause pain and infection in the tooth. Fusobacterium nucleatum was always found predominantly in failed root canal treatments.

OBJECTIVE

The aim of the present study was to quantify Fusobacterium nucleatum at the inner and peripheral half of coronal, middle and apical region of the root by using real-time polymerase chain reaction (qPCR).

METHODS

Extracted maxillary incisors were taken. After shaping and cleaning, the root canals were inoculated with Fusobacterium nucleatum. Samples were taken from both the inner and peripheral halves of dentin. The inoculated teeth were maintained in anaerobic jars for two weeks, and the bacterial isolates were changed every third day. The quantification was done using qPCR.

RESULTS

The cycle threshold (Ct) value in all groups showed the presence of Fusobacterium nucleatum.

CONCLUSION

Fusobacterium nucleatum penetrates to the entire thickness of dentin in the middle and apical region. The coaggregation with other microorganisms could be responsible for the symptomatic endodontic patients.

Lipopolysaccharide, a possible molecular mediator between periodontitis and coronary artery disease

AIM

We aimed to study how lipopolysaccharide (LPS) in saliva and serum associates with each other, periodontal microbial burden, periodontitis and coronary artery disease (CAD).

MATERIALS AND METHODS

The used Parogene cohort comprised N = 505 Finnish adults. Coronary diagnosis was acquired by coronary angiography, and the main outcomes were as follows: no significant CAD (n = 123), stable CAD (n = 184) and acute coronary syndrome (n = 169). Periodontitis was defined according to clinical and radiographic examinations. Levels for 75 strains of subgingival bacteria were determined by checkerboard DNA-DNA hybridization. Saliva and serum LPS activity was analysed by Limulus amebocyte lysate assay.

RESULTS

The level of 11 bacterial strains, which were mainly oral and respiratory Gram-negative species, associated with salivary LPS levels in an age- and gender-adjusted linear regression. A total of 4.9% of the serum LPS, that is endotoxemia, variation was explainable by saliva LPS among patients with periodontitis (n = 247, R²  = .049, Pearson's r = .222, p < .001). Endotoxemia associated with stable CAD in a confounder adjusted multinomial logistic regression model (OR 1.99, 95% CI 1.04-3.81, p = .039, 3rd tertile).

CONCLUSIONS

In particular in periodontitis patients, subgingival microbial burden contributes to endotoxemia. LPS is a possible molecular mediator between periodontitis and CAD.

Metagenomic analysis of faecal microbiome as a tool towards targeted non-invasive biomarkers for colorectal cancer

OBJECTIVE

To evaluate the potential for diagnosing colorectal cancer (CRC) from faecal metagenomes.

DESIGN

We performed metagenome-wide association studies on faecal samples from 74 patients with CRC and 54 controls from China, and validated the results in 16 patients and 24 controls from Denmark. We further validated the biomarkers in two published cohorts from France and Austria. Finally, we employed targeted quantitative PCR (qPCR) assays to evaluate diagnostic potential of selected biomarkers in an independent Chinese cohort of 47 patients and 109 controls.

RESULTS

Besides confirming known associations of Fusobacterium nucleatum and Peptostreptococcus stomatis with CRC, we found significant associations with several species, including Parvimonas micra and Solobacterium moorei. We identified 20 microbial gene markers that differentiated CRC and control microbiomes, and validated 4 markers in the Danish cohort. In the French and Austrian cohorts, these four genes distinguished CRC metagenomes from controls with areas under the receiver-operating curve (AUC) of 0.72 and 0.77, respectively. qPCR measurements of two of these genes accurately classified patients with CRC in the independent Chinese cohort with AUC=0.84 and OR of 23. These genes were enriched in early-stage (I-II) patient microbiomes, highlighting the potential for using faecal metagenomic biomarkers for early diagnosis of CRC.

CONCLUSIONS

We present the first metagenomic profiling study of CRC faecal microbiomes to discover and validate microbial biomarkers in ethnically different cohorts, and to independently validate selected biomarkers using an affordable clinically relevant technology. Our study thus takes a step further towards affordable non-invasive early diagnostic biomarkers for CRC from faecal samples.

Binding properties of Treponema denticola lipooligosaccharide

BACKGROUND AND OBJECTIVE

The cell-surface lipooligosaccharide (LOS) of Treponema denticola possesses several biological properties. The aim of this study was to investigate the binding properties of T. denticola LOS to extracellular matrix (ECM) proteins, mucosal cells, and oral bacteria.

DESIGN

LOS was isolated from T. denticola and labeled with tritium. Tritium-labeled LOS was placed in ECM protein-, epithelial cell-, fibroblast-, or bacterium-coated wells of a 96-well microplate. Following incubation, unattached LOS was removed by extensive washing, and the amount of bound LOS was determined by measuring the radioactivity in the wells. Peptostreptococcus micros coated with LOS was used to stimulate fibroblasts, and the secretion of interleukin-6 (IL-6) and interleukin-8 (IL-8) by the fibroblasts was determined by ELISA.

RESULTS

T. denticola LOS had a high affinity for laminin. It also bound to gingival epithelial cells and fibroblasts. Soluble CD14 significantly increased the binding of LOS to fibroblasts. More LOS bound to P. micros than the other oral bacterial species tested. Stimulating fibroblasts with LOS-coated P. micros induced the secretion of IL-6 and IL-8.

CONCLUSIONS

Our study provided evidence that T. denticola LOS possesses the capacity to bind to ECM proteins, mucosal cells, and oral bacteria. In addition, LOS binding to bacteria may increase their pro-inflammatory potential.

Gram-positive anaerobic cocci--commensals and opportunistic pathogens

Among the Gram-positive anaerobic bacteria associated with clinical infections, the Gram-positive anaerobic cocci (GPAC) are the most prominent and account for approximately 25-30% of all isolated anaerobic bacteria from clinical specimens. Still, routine culture and identification of these slowly growing anaerobes to the species level has been limited in the diagnostic laboratory, mainly due to the requirement of prolonged incubation times and time-consuming phenotypic identification. In addition, GPAC are mostly isolated from polymicrobial infections with known pathogens and therefore their relevance has often been overlooked. However, through improvements in diagnostic and in particular molecular techniques, the isolation and identification of individual genera and species of GPAC associated with specific infections have been enhanced. Furthermore, the taxonomy of GPAC has undergone considerable changes over the years, mainly due to the development of molecular identification methods. Existing species have been renamed and novel species have been added, resulting in changes of the nomenclature. As the abundance and significance of GPAC in clinical infections grow, knowledge of virulence factors and antibiotic resistance patterns of different species becomes more important. The present review describes recent advances of GPAC and what is known of the biology and pathogenic effects of Anaerococcus, Finegoldia, Parvimonas, Peptoniphilus and Peptostreptococcus, the most important GPAC genera isolated from human infections.

Peptostreptococcus micros cell wall elicits a pro-inflammatory response in human macrophages

Peptostreptococcus micros is a Gram-positive anaerobic bacterium associated with periodontitis, a chronic inflammatory disease affecting tooth-supporting tissues. In the present study, we investigated the response of human macrophages to stimulation with a cell wall preparation from P. micros. In addition, the effect of the preparation on the phosphorylation of macrophage kinases was studied. The preparation, which was non-toxic for macrophages, significantly increased the secretion of the pro-inflammatory cytokines TNF-alpha, IL-1beta and IL-6. It also increased the secretion of two potent chemokines IL-8 and, to a lesser extent, RANTES. Lastly, stimulation of macrophages by the P. micros cell wall preparation induced a significant increase in MMP-9 secretion but had no effect on the production of prostaglandin E2. The phosphorylation of macrophage kinases, including cAMP-dependent protein-serine kinase (PKA) catalytic subunit beta, G protein-coupled receptor-serine kinase 2, mitogen-activated protein-serine kinase p38 alpha (p38a MAPK), extracellular regulated protein-serine kinase 2 (ERK2) and Jun N-terminus protein-serine kinases (JNK), increased following stimulation with cell wall. In summary, our study showed that the P. micros cell wall preparation induced intracellular signaling pathways, leading to an increased production of pro-inflammatory cytokines, chemokines and MMP-9 by macrophages.

Effect of Tumor Necrosis Factor-α Gene Polymorphism on Peri-Implant Bone Loss Following Prosthetic Reconstruction

PURPOSE

The present study investigates the association between a specific polymorphism in the tumor necrosis factor (TNF)-alpha gene, consisting of allele 2 of TNF-alpha-308, and peri-implant bone loss following prosthetic reconstruction.

MATERIALS AND METHODS

This case-control study included 36 patients (20 women, 16 men; mean age 46 years) who had used implant-supported prostheses for a minimum of 6 months and a maximum of 31 months. The patients were nonsmoking, white Caucasian Brazilians, in good general health, and were not receiving medication. In the case group, patients exhibited 1 or more implants with a diagnosis of peri-implant bone loss following prosthetic reconstruction; control patients had 1 or more healthy implants.

RESULTS

Polymorphism in the TNF-alpha gene, allele 2 of TNF-alpha, was not associated with an increased risk for peri-implant bone loss following prosthetic reconstruction (P=0.19; chi2=1.71; df=1), although 21.1% of the subjects carried allele in the control group 2, and 41.2% carried allele 2 in the case group.

CONCLUSIONS

Polymorphism in allele 2 of the TNF-alpha-308 gene is not associated with an increased risk for peri-implant bone loss following prosthetic reconstruction. However, further studies based on a greater number of patients are necessary.