Presence of Aggregatibacter actinomycetemcomitans in young individuals: a 16-year clinical and microbiological follow-up study

O-Polysaccharide Plays a Major Role on the Virulence and Immunostimulatory Potential of Aggregatibacter actinomycetemcomitans During Periodontal Infection

Aggregatibacter actinomycetemcomitans is a Gram-negative oral bacterium with high immunostimulatory and pathogenic potential involved in the onset and progression of periodontitis, a chronic disease characterized by aberrant immune responses followed by tooth-supporting bone resorption, which eventually leads to tooth loss. While several studies have provided evidence related to the virulence factors of A. actinomycetemcomitans involved in the host cell death and immune evasion, such as its most studied primate-specific virulence factor, leukotoxin, the role of specific lipopolysaccharide (LPS) domains remain poorly understood. Here, we analyzed the role of the immunodominant domain of the LPS of A. actinomycetemcomitans termed O-polysaccharide (O-PS), which differentiates the distinct bacterial serotypes based on its antigenicity. To determine the role of the O-PS in the immunogenicity and virulence of A. actinomycetemcomitans during periodontitis, we analyzed the in vivo and in vitro effect of an O-PS-defective transposon mutant serotype b strain, characterized by the deletion of the rmlC gene encoding the α-L-rhamnose sugar biosynthetic enzyme. Induction of experimental periodontitis using the O-PS-defective rmlC mutant strain resulted in lower tooth-supporting bone resorption, infiltration of Th1, Th17, and Th22 lymphocytes, and expression of Ahr, Il1b, Il17, Il23, Tlr4, and RANKL (Tnfsf11) in the periodontal lesions as compared with the wild-type A. actinomycetemcomitans strain. In addition, the O-PS-defective rmlC mutant strain led to impaired activation of antigen-presenting cells, with less expression of the co-stimulatory molecules CD40 and CD80 in B lymphocytes and dendritic cells, and downregulated expression of Tnfa and Il1b in splenocytes. In conclusion, these data demonstrate that the O-PS from the serotype b of A. actinomycetemcomitans plays a key role in the capacity of the bacterium to prime oral innate and adaptive immune responses, by triggering the Th1 and Th17-driven tooth-supporting bone resorption during periodontitis.

Grade C molar-incisor pattern periodontitis subgingival microbial profile before and after treatment

Aim: This study evaluated the influence of periodontal therapy on the microbiological profile of individuals with Grade C Molar-Incisor Pattern Periodontitis (C/MIP).

Methods: Fifty-three African-American participants between the ages of 5–25, diagnosed with C/MIP were included. Patients underwent full mouth mechanical debridement with systemic antibiotics (metronidazole 250 mg + amoxicillin 500 mg, tid, 7 days). Subgingival samples were collected from a diseased and a healthy site from each individual prior to treatment and at 3, 6, 12, 18 and 24 months after therapy from the same sites. Samples were subjected to a 16S rRNA gene based-microarray.

Results: Treatment was effective in reducing the main clinical parameters of disease. Aggregatibacter actinomycetemcomitans (A.a.) was the strongest species associated with diseased sites. Other species associated with diseased sites were Treponema lecithinolyticum and Tannerella forsythia. Species associated with healthy sites were Rothia dentocariosa/mucilaginosa, Eubacterium yurii, Parvimonas micra, Veillonella spp., Selenomonas spp., and Streptococcus spp. Overall, treatment was effective in strongly reducing A.a. and other key pathogens, as well as increasing health-associated species. These changes were maintained for at least 6 months.

Conclusions:Treatment reduced putative disease-associated species, particularly A.a., and shifted the microbial profile to more closely resemble a healthy-site profile. (Clinicaltrials.gov registration #NCT01330719).

Cranberry Proanthocyanidins Neutralize the Effects of Aggregatibacter actinomycetemcomitans Leukotoxin

Aggregatibacter actinomycetemcomitans is a Gram-negative bacterium that has been strongly associated with localized aggressive periodontitis. The capacity of A. actinomycetemcomitans to produce a leukotoxin (LtxA) that activates pyroptosis in macrophages and induces the release of endogenous danger signals is thought to play a key role in the disease process. The aim of the present study was to investigate the effects of cranberry proanthocyanidins (PACs) on gene expression and cytotoxic activities of LtxA. We showed that cranberry PACs dose-dependently attenuate the expression of genes making up the leukotoxin operon, including ltxB and ltxC, in the two strains of A. actinomycetemcomitans tested. Cranberry PACs (≥62.5 µg/mL) protected macrophages against the cytotoxic effect of purified LtxA. Moreover, cranberry PACs reduced caspase-1 activation in LtxA-treated macrophages and consequently decreased the release of both IL-1β and IL-18, which are known as damage-associated molecular patterns (DAMPs) and contribute to the progression of periodontitis by increasing cell migration and osteoclastogenesis. In addition, cranberry PACs reduced the expression of genes encoding the P2X7 receptor and NALP3 (NACHT, LRR and PYD domains-containing protein 3), which play key roles in pore formation and cell death. Lastly, cranberry PACs blocked the binding of LtxA to macrophages and consequently reduced the LtxA-mediated cytotoxicity. In summary, the present study showed that cranberry PACs reduced LtxA gene expression in A. actinomycetemcomitans and neutralized the cytolytic and pro-inflammatory responses of human macrophages treated with LtxA. Given these properties, cranberry PACs may represent promising molecules for prevention and treatment of the aggressive form of periodontitis caused by A. actinomycetemcomitans.

Multidisciplinary Clinical Management of a Localized Aggressive Periodontitis diagnosed in a Child with Glanzmann's Thrombasthenia

Localized aggressive periodontitis (LAP) in child involving primary dentition is a rare disease. The main characteristics of LAP are deep periodontal pockets, bone loss, tooth mobility, and, sometimes, spontaneous tooth loss. The LAP involves only some specific teeth. Glanzmann’s thrombasthenia (GT) is a rare autosomal recessive bleeding disorder. The paper’s aim is to present the case of a 5-year-old girl with GT presenting LAP, and discuss her clinical management.

How to cite this article: Prud’homme T, Roy E, Soueidan A, Fouassier M, Dajean-Trutaud S, Badran Z. Multidisciplinary Clinical Management of a Localized Aggressive Periodontitis diagnosed in a Child with Glanzmann’s Thrombasthenia. Int J Clin Pediatr Dent 2018;11(4):344-348.

Serotypes of Aggregatibacter actinomycetemcomitans in relation to periodontal status and assessment of leukotoxin in periodontal disease: A clinico-microbiological study

Context:

Aggregatibacter actinomycetemcomitans (A.a) serotypes may add some important information of the pathogenetic background of periodontal infections. A.a leukotoxin is an important virulence factor in the pathogenesis of periodontal disease and its rate of progression. When compared to minimally leukotoxic strains, variants of A.a highly leukotoxic strains produce 10–20 times more leukotoxin.

Aims:

The aim of the present study was to detect serotypes a, b, c, d, and e of A.a its leukotoxin and find its correlation with periodontal status.

Settings and Design:

Microbiological analysis and cross-sectional study.

Materials and Methods:

A total of 80 subjects (40 chronic periodontitis and 40 aggressive periodontitis) in the age range of 14–55 years were selected. Subgingival plaque samples were collected and checked for the presence of A.a. Following isolation of the organism, detection of the serotypes and leukotoxin assessment was done.

Statistical Analysis Used:

The proportions of A.a were calculated using descriptive statistics in terms of percentage. Chi-square test was used to find association between serotype, leukotoxin, and periodontal disease in individual group.

Results:

Out of 80 plaque samples, 45% tested positive for A.a. serotype b was detected in 33.33%, whereas serotype e in 8.33% samples and serotype c in 2.77% samples. Serotypes a and d were not detected in any of the samples. A combination of serotypes was seen in 47.22% of the sites. Of these 76.47% showed a combination of 2 serotypes, while 23.52%showed a combination of 3 serotypes. 8.33% showed untypable serotype. All samples had low-toxic variants of A.a.

Conclusions:

Serotype b and serotype e were predominant in chronic periodontitis, and serotype b was predominant in aggressive periodontitis. An association could be present between serotype and periodontal disease.

Putative periodontopathic bacteria and herpes viruses interactions in the subgingival plaque of patients with aggressive periodontitis and healthy controls

The microbial profile of aggressive periodontitis patients is considered to be complex with variations among populations in different geographical areas. The aim of this study was to assess the presences of 4 putative periodontopathic bacteria (Aggregatibacter actinomycetemcomitans, Porphyromonas gingivalis, Tannerella forsythia, and Treponema denticola) and 2 periodontal herpes viruses (Epstein-Barr virus type 1 [EBV-1] and human cytomegalovirus [HMCV]) in subgingival plaque of Sudanese subjects with aggressive periodontitis and healthy controls. The study group consisted of 34 subjects, 17 aggressive periodontitis patients and 17 periodontally healthy controls (14-19 years of age). Pooled subgingival plaque samples were collected and analyzed for detection of bacteria and viruses using loop-mediated isothermal amplification. Prevalence of subgingival A. actinomycetemcomitans, HCMV, and P. gingivalis were significantly higher among aggressive periodontitis patients than periodontally healthy controls. Coinfection with A. actinomycetemcomitans, HCMV, and/or EBV-1 was restricted to the cases. Increased risk of aggressive periodontitis was the highest when A. actinomycetemcomitans was detected together with EBV-1 (OD 49.0, 95% CI [2.5, 948.7], p = .01) and HCMV (OD 39.1, 95% CI [2.0, 754.6], p = .02). In Sudanese patients, A. actinomycetemcomitans and HCMV were the most associated test pathogens with aggressive periodontitis.

Actinomyces radicidentis and Actinomyces haliotis, coccoid Actinomyces species isolated from the human oral cavity

There are few reports on the bacterial species Actinomyces radicidentis in the literature. In this study, putative A. radicidentis isolates were collected from 16 root canal samples from 601 examined patients. The isolates were examined by biochemical tests, 16S rRNA gene sequencing, Arbitrarily-primed (AP-) PCR, antibiotic susceptibility testing, and MALDI-TOF analyses. In parallel, two A. radicidentis reference strains and two putative A. radicidentis isolates from United Kingdom were tested. Sixteen of the 18 isolates were confirmed as A. radicidentis. The remaining two isolates, both of which were isolated from root canals (one from Sweden and the other from the UK), but were identified as Actinomyces haliotis by sequencing ∼ 1300 base pairs of the 16S rRNA-gene. This isolates had a divergent, but between them similar, AP-PCR pattern, and a common distribution of sequence signatures in the 16S rRNA gene, but were not identified by MALDI-TOF. A. haliotis is a close relative to A. radicidentis, hitherto only been described from a sea-snail. The identity of A. haliotis was confirmed by a phylogenetic tree based on 16S rRNA gene sequences with species specific sequences included, and by additional biochemical tests. The examined bacteria exhibited similar antibiotic susceptibility patterns when tested for 10 separate antibiotic classes with E-tests (bioMérieux). The MIC₉₀ for β-lactams (benzylpenicillin and cefuroxime) and vancomycin was 0.5 mg/L, for colistin and ciprofloxacin 8 mg/mL and for the other antibiotic classes ≤ 25 mg/mL The isolation of A. haliotis from infected dental root canals cast doubt on the accepted opinion that all Actinomyces infections have an endogenous source.

Age-related prevalence and characteristics of Aggregatibacter actinomycetemcomitans in periodontitis patients living in Sweden

Background: The presence of Aggregatibacter actinomycetemcomitans in patients with periodontitis has been extensively studied for decades.

Objective: To study the prevalence of A. actinomycetemcomitans in younger and older periodontitis patients and to genetically characterize isolates of this bacterium.

Design: Data from microbiological analyses of 3459 subgingival plaque samples collected from 1445 patients, 337 ‘younger’ patients (≤35 yrs) and 1108 ‘older’ patients (>35 yrs) during 15 years (2000–2014), has been summerized. Isolates of A. actinomycetemcomitans were serotyped, leukotoxin promoter typed (JP2 and non JP2) and arbitrarily primed PCR (AP-PCR) genotyped. The origin of the JP2 genotype detected in the study population was determined.

Results: The prevalence of A. actinomycetemcomitans was higher among younger than older patients and samples from the younger patients contained higher proportions of the bacterium. Serotype b was more prevalent among younger patients and the majorty of these isolates was from the same AP-PCR genotype. The JP2 genotype was detected in 1.2% of the patients, and the majority of these carriers were of non-African origin.

Conslusions: For presence and charcteristics of A. actinomycetemcomitans in clinical samples the age of the carriers were a discriminating factor. Additional, apparently non-African carriers of the JP2 genotype of A. actinomycetemcomitans were identified.

Microbiology of aggressive periodontitis

For decades, Aggregatibacter actinomycetemcomitans has been considered the most likely etiologic agent in aggressive periodontitis. Implementation of DNA-based microbiologic methodologies has considerably improved our understanding of the composition of subgingival biofilms, and advanced open-ended molecular techniques even allow for genome mapping of the whole bacterial spectrum in a sample and characterization of both the cultivable and not-yet-cultivable microbiota associated with periodontal health and disease. Currently, A. actinomycetemcomitans is regarded as a minor component of the resident oral microbiota and as an opportunistic pathogen in some individuals. Its specific JP2 clone, however, shows properties of a true exogenous pathogen and has an important role in the development of aggressive periodontitis in certain populations. Still, limited data exist on the impact of other microbes specifically in aggressive periodontitis. Despite a wide heterogeneity of bacteria, especially in subgingival samples collected from patients, bacteria of the red complex in particular, and those of the orange complex, are considered as potential pathogens in generalized aggressive periodontitis. These types of bacterial findings closely resemble those found for chronic periodontitis, representing a mixed polymicrobial infection without a clear association with any specific microorganism. In aggressive periodontitis, the role of novel and not-yet-cultivable bacteria has not yet been elucidated. There are geographic and ethnic differences in the carriage of periodontitis-associated microorganisms, and they need to be taken into account when comparing study reports on periodontal microbiology in different study populations. In the present review, we provide an overview on the colonization of potential periodontal pathogens in childhood and adolescence, and on specific microorganisms that have been suspected for their role in the initiation and progression of aggressive forms of periodontal disease.

Detection of a 640-bp deletion in the Aggregatibacter actinomycetemcomitans leukotoxin promoter region in isolates from an adolescent of Ethiopian origin

The expression of the leukotoxin of Aggregatibacter actinomycetemcomitans is regulated by the leukotoxin promoter. A 530-bp deletion or an 886-bp insertion sequence (IS) element in this region has earlier been described in highly leukotoxic isolates. Here, we report on highly leukotoxic isolate with a 640-bp deletion, which was detected in an adolescent of Ethiopian origin.

Integration of non-oral bacteria into in vitro oral biofilms

Biofilms are polymicrobial communities that grow on surfaces in nature. Oral bacteria can spontaneously form biofilms on the surface of teeth, which may compromise the health of the teeth, or their surrounding (periodontal) tissues. While the oral bacteria exhibit high tropism for their specialized ecological niche, it is not clear if bacteria that are not part of the normal oral microbiota can efficiently colonize and grow within oral biofilms. By using an in vitro "supragingival" biofilm model of 6 oral species, this study aimed to investigate if 3 individual bacterial species that are not part of the normal oral microbiota (Eschericia coli, Staphylococcus aureus, Enterococcus faecails) and one not previously tested oral species (Aggregatibacter actinomycetemcomitans) can be incorporated into this established supragingival biofilm model. Staphylococcus aureus and A. actinomycetemcomitans were able to grow efficiently in the biofilm, without disrupting the growth of the remaining species. They localized in sparse small aggregates within the biofilm mass. Enterococcus faecalis and E. coli were both able to populate the biofilm at high numbers, and suppressed the growth of A. oris and S. mutants. Enterococcus faecalis was arranged in a chain-like conformation, whereas E. coli was densely and evenly spread throughout the biofilm mass. In conclusion, it is possible for selected species that are not part of the normal oral microbiota to be introduced into an oral biofilm, under the given experimental micro-environmental conditions. Moreover, the equilibrated incorporation of A. actinomycetemcomitans and S. aureus in this oral biofilm model could be a useful tool in the study of aggressive periodontitis and peri-implantitis, in which these organisms are involved, respectively.

Cytolethal Distending Toxin: A Unique Variation on the AB Toxin Paradigm

Some of the most potent toxins produced by plants and bacteria are members of a large family known as the AB toxins. AB toxins are generally characterized by a heterogenous complex consisting of two protein chains arranged in various monomeric or polymeric configurations. The newest class within this superfamily is the cytolethal distending toxin (Cdt). The Cdt is represented by a subfamily of toxins produced by a group of taxonomically distinct Gram negative bacteria. Members of this subfamily have a related AB-type chain or subunit configuration and properties distinctive to the AB paradigm. In this review, the unique structural and cytotoxic properties of the Cdt subfamily, target cell specificities, intoxication pathway, modes of action, and relationship to the AB toxin superfamily are compared and contrasted.

Breaking the Gingival Epithelial Barrier: Role of the Aggregatibacter actinomycetemcomitans Cytolethal Distending Toxin in Oral Infectious Disease

The Gram-negative bacterium Aggregatibacter actinomycetemcomitans is part of the HACEK group that causes infective endocarditis, a constituent of the oral flora that promotes some forms of periodontal disease and a member of the family of species that secrete a cytolethal distending toxin (Cdt). The family of bacteria that express the cdt genes participate in diseases that involve the disruption of a mucosal or epithelial layer. In vitro studies have shown that human gingival epithelial cells (HGEC) are native targets of the Cdt that typically induces DNA damage that signals growth arrest at the G₂/M interphase of the cell cycle. The gingival epithelium is an early line of defense in the oral cavity against microbial assault. When damaged, bacteria collectively gain entry into the underlying connective tissue where microbial products can affect processes and pathways in infiltrating inflammatory cells culminating in the destruction of the attachment apparatus of the tooth. One approach has been the use of an ex vivo gingival explant model to assess the effects of the Cdt on the morphology and integrity of the tissue. The goal of this review is to provide an overview of these studies and to critically examine the potential contribution of the Cdt to the breakdown of the protective gingival barrier.

Serotypes of Aggregatibacter actinomycetemcomitans in relation to periodontal status and geographic origin of individuals-a review of the literature

Objectives: Several studies have focused on the relationship among serotype distribution, ethnical status and geographic populations, and periodontal conditions. Studies that have investigated the prevalence and the distribution of A. actinomycetemcomitans serotypes and the relation between the different serotypes of the bacterium and periodontal status were reviewed. Material and Methods: A systematic literature search for publications regarding the distribution of A. actinomycetemcomitans serotypes in subgingival samples of periodontitis patients and periodontally healthy subjects by employing polymerase chain reaction (PCR) was conducted. Results: From the 85 studies identified in the first analysis, only 12 met all inclusion and exclusion criteria. Clinical isolates from diverse geographic populations with different periodontal conditions were evaluated. Serotypes a, b and c were largely found, and serotype c was the most prevalent. They were isolated from various periodontal conditions, including aggressive periodontitis. Conclusions: The available literature suggests that serotypes a, b, and c are globally dominant, serotypes d and e are rare, and the prevalence of the most recently identified serotype fis still unknown. It is widely accepted that distribution patterns of A. actinomycetemcomitans vary among subjects of different ethnicity and geographic regions. The correlation of different serotypes with various periodontal conditions remains unclear.

Key words:Aggregatibacter actinomycetemcomitans, serotypes, periodontal disease, prevalence.

Mast cells act as phagocytes against the periodontopathogen Aggregatibacter actinomycetemcomitans

BACKGROUND

Evidence to date shows that mast cells play a critical role in immune defenses against infectious agents, but there have been no reports about involvement of these cells in eliminating periodontopathogens. In this study, the phagocytic ability of mast cells against Aggregatibacter actinomycetemcomitans compared with macrophages is evaluated.

METHODS

In vitro phagocytic assays were conducted using murine mast cells and macrophages, incubated with A. actinomycetemcomitans, either opsonized or not, with different bacterial load ratios. After 1 hour, cells were stained with acridine orange and assessed by confocal laser-scanning electron microscopy.

RESULTS

Phagocytic ability of murine mast cells against A. actinomycetemcomitans was confirmed. In addition, the percentage of mast cells with internalized bacteria was higher in the absence of opsonization than in the presence of opsonization. Both cell types showed significant phagocytic activity against A. actinomycetemcomitans. However, the percentage of mast cells with non-opsonized bacteria was higher than that of macrophages with opsonized bacteria in one of the ratios (1:10).

CONCLUSIONS

This is the first report about the participation of murine mast cells as phagocytes against A. actinomycetemcomitans, mainly in the absence of opsonization with human serum. Our results may indicate that mast cells act as professional phagocytes in the pathogenesis of biofilm-associated periodontal disease.

The essential role of toll like receptor-4 in the control of Aggregatibacter actinomycetemcomitans infection in mice

OBJECTIVE

Aggregatibacter actinomycetemcomitans is an oral Gram-negative bacterium that contributes to periodontitis progression. Isolated antigens from A. actinomycetemcomitans could be activating innate immune cells through Toll-like receptors (TLRs). In this study, we evaluated the role of TLR4 in the control of A. actinomycetemcomitans infection.

MATERIAL AND METHODS

We examined the mechanisms that modulate the outcome of A. actinomycetemcomitans-induced periodontal disease in TLR4(-/-) mice. The production of cytokines was evaluated by ELISA. The bacterial load was determined by counting the number of colony-forming units per gram of tissue.

RESULTS

The results showed that TLR4-deficient mice developed less severe periodontitis after A. actinomycetemcomitans infection, characterized by significantly lower bone loss and inflammatory cell migration to periodontal tissues. However, the absence of TLR4 facilitated the A. actinomycetemcomitans dissemination. Myeloperoxidase activity was diminished in the periodontal tissue of TLR4(-/-) mice. We observed a significant reduction in the production of tumour necrosis factor-alpha (TNF-alpha) and interleukin (IL)-1beta in the periodontal tissue of TLR4(-/-) mice.

CONCLUSION

The results of this study highlighted the role of TLR4 in controlling A. actinomycetemcomitans infection.