Diminished treatment response of periodontally diseased patients infected with the JP2 clone of Aggregatibacter (Actinobacillus) actinomycetemcomitans

Toxin-triggered liposomes for the controlled release of antibiotics to treat infections associated with the gram-negative bacterium, Aggregatibacter actinomycetemcomitans

Antibiotic resistance has become an urgent threat to health care in recent years. The use of drug delivery systems provides advantages over conventional administration of antibiotics and can slow the development of antibiotic resistance. In the current study, we developed a toxin-triggered liposomal antibiotic delivery system, in which the drug release is enabled by the leukotoxin (LtxA) produced by the Gram-negative pathogen, Aggregatibacter actinomycetemcomitans. LtxA has previously been shown to mediate membrane disruption by promoting a lipid phase change in nonlamellar lipids, such as 1,2-dioleoyl-sn-glycero-3-phosphoethanolamine-N-methyl (N-methyl-DOPE). In addition, LtxA has been observed to bind strongly and nearly irreversibly to membranes containing large amounts of cholesterol. Here, we designed a liposomal delivery system composed of N-methyl-DOPE and cholesterol to take advantage of these interactions. Specifically, we hypothesized that liposomes composed of N-methyl-DOPE and cholesterol, encapsulating antibiotics, would be sensitive to LtxA, enabling controlled antibiotic release. We observed that liposomes composed of N-methyl-DOPE were sensitive to the presence of low concentrations of LtxA, and cholesterol increased the extent and kinetics of content release. The liposomes were stable under various storage conditions for at least 7 days. Finally, we showed that antibiotic release occurs selectively in the presence of an LtxA-producing strain of A. actinomycetemcomitans but not in the presence of a non-LtxA-expressing strain. Together, these results demonstrate that the designed liposomal vehicle enables toxin-triggered delivery of antibiotics to LtxA-producing strains of A. actinomycetemcomitans.

A bivalent outer membrane vesicle-based intranasal vaccine to prevent infection of periodontopathic bacteria

Periodontal disease has become a serious public health problem, not only causing tooth loss, but also inducing chronic disorders of extra-oral organs. The present study assessed an intranasal vaccine strategy to prevent periodontal disease using outer membrane vesicles (OMVs) of two major periodontopathic bacteria, Porphyromonas gingivalis (Pg) and Aggregatibacter actinomycetemcomitans (Aa). We compared the morphology, composition, and immune activity between OMVs of Pg strain ATCC 33277 and Aa strain Y4. Aa OMVs had a smoother surface and stronger lipid A activity compared to Pg OMVs. The in vitro immune activity elicited by Aa OMVs in macrophage-like cells was remarkably stronger than that of Pg OMVs. Intranasal immunization of mice with Aa OMVs alone resulted in robust, humoral immune responses in blood and saliva. Despites the intrinsically low mucosal immunogenicity of Pg OMVs alone, using Aa OMVs as a mucosal adjuvant strongly enhanced Pg-specific immune responses, resulting in both serum IgG and salivary IgA, both of which aggregated Pg and Aa cells. Furthermore, Aa OMVs were found to be a more potent mucosal adjuvant than Poly(I:C) in the context of enhancing the production of Pg-specific IgG (especially IgG2a) and IgA. In addition, in a randomized, blinded study, mice oral challenged with Pg and Aa after intranasal immunization with Pg OMVs and Aa OMVs had significantly decreased numbers of both microorganisms compared to mock-immunized mice. Furthermore, in an intracerebral injection mouse model, there were no serious adverse effects on the brain even after administrating a dose of OMVs as same as that used for intranasal administration. Taken together, the bivalent OMV intranasal vaccine may be effective in preventing colonization of periodontopathic bacteria in the oral cavity and related systemic disorders associated with periodontal diseases.

Aggregatibacter actinomycetemcomitans serotypes and JP2 outcomes related to clinical status over 6 years under periodontal maintenance therapy

OBJECTIVE

This 6-year study evaluatedAggregatibacter actinomycetemcomitans outcomes and their relationship to clinical status.

DESIGN

From the eligible individuals (23-70 years of age), 31 regular compliers (between-visit interval < 6 months) were randomly selected and matched for age/sex with 31 irregular compliers (between-visit interval > 6 months). Periodontal clinical examination and subgingival samples were obtained 5 times: T1 (baseline), T2 (after active periodontal therapy), T3 (2 years), T4 (4 years), and T5 (6 years). Total bacteria load, A. actinomycetemcomitans, and red complex species Porphyromonas gingivalis, Tannerella forsythia, Treponema denticola levels were determined by qPCR while PCR was used to determine the occurrence of the a-b-c-d-e-f-g serotypes and the JP2 clone of A. actinomycetemcomitans. Data between groups was compared over time.

RESULTS

At baseline PCR revealed A. actinomycetemcomitans prevalence of 9.7 % and JP2 prevalence of 6.7 %. A. actinomycetemcomitans qPCR levels were higher among individuals < 35 years of age and increased at T2 in irregular compliers. At in irregular compliers at the three follow-up visits. Serotypes a, d, and f showed greater values in at least one follow-up visit in regular compliers. A. actinomycetemcomitans showed negative correlation with probing depth (PD) while serotype b showed negative correlations with PD, PI, clinical attachment level and red complex.

CONCLUSIONS

Longitudinally, compliance during PMT contributed to lower A. actinomycetemcomitans levels with some degree of correlation with clinical status. However, this study failed to report any positive effect on the occurrence of the most virulent representatives, i.e. serotype b and the JP2 clone.

JP2 Genotype of Aggregatibacter actinomycetemcomitans in Caucasian Patients: A Presentation of Two Cases

Aggregatibacter actinomycetemcomitans is a key pathogen that has been associated with periodontal disease. Its most important virulence factor is a leukotoxin capable of inactivating immune cells. The JP2 genotype of Aggregatibacter actinomycetemcomitans shows enhanced leukotoxic activity and is mostly present in individuals of North and West African origin with severe periodontitis. In this paper, two cases of Caucasians diagnosed with the JP2 genotype are presented. A 50-year-old female patient had three approximal sites with ≥ 6 mm clinical attachment loss (CAL) and eight sites with probing depth (PD) ≥ 5 mm. Microbiological diagnostics revealed A. actinomycetemcomitans JP2 genotype, but not Porphyromonas gingivalis. This JP2 genotype was highly leukotoxic to monocytic cells. The second case was a 55-year-old female patient with CAL of > 5 mm at all molars and PD of up to 12 mm. A. actinomycetemcomitans JP2 was identified, but not P. gingivalis. Her husband originated from North-Africa. In him, no A. actinomycetemcomitans was detected, but their 17-year-old daughter was diagnosed with periodontitis and was found to be positive for the JP2 genotype. Both patients were successfully treated with adjunctive antibiotics and the JP2 genotype was eliminated. In summary, here, the microbiological diagnosis was key for the treatment with adjunctive antibiotics.

Effects of Monolaurin on Oral Microbe-Host Transcriptome and Metabolome

The aim of this in vitro study was to evaluate the effects of monolaurin against Aggregatibacter actinomycetemcomitans (Aa) and determine their effects on the host transcriptome and metabolome, using an oral cell/bacteria co-culture dual-chamber model to mimic the human periodontium. For this, the Aa, was applied to cross the monolayer of epithelial keratinocytes (OBA-9) to reach the fibroblasts layer (HGF-1) in the basal chamber. The Monolaurin treatments (25 or 50 μM) were added immediately after the inoculation of the dual-chamber with Aa. After 24 h, the transcriptional factors and metabolites produced were quantified in the remaining cell layers (insert and basal chamber) and in supernatant released from the cells. The genes IL-1α, IL-6, IL-18, and TNF analyzed in HGF-1 concentrations showed a decreased expression when treated with both concentration of Monolaurin. In keratinocytes, the genes IL-6, IL-18, and TNF presented a higher expression and the expression of IL-1α decreased when treated with the two cited concentrations. The production of glycerol and pyruvic acid increased, and the 2-deoxytetronic acid NIST, 4-aminobutyric acid, pinitol and glyceric acid, presented lower concentrations because of the treatment with 25 and/or 50 μM of Monolaurin. Use of monolaurin modulated the immune response and metabolite production when administered for 24 h in a dual-chamber model inoculated with A. actinomycetemcomitans. In summary, this study indicates that monolaurin had antimicrobial activity and modulated the host immune response and metabolite production when administered for 24 h in a dual-chamber model inoculated with A. actinomycetemcomitans.

Aggregatibacter (Actinobacillus) actimycetemcomitans leukotoxin and human periodontitis - A historic review with emphasis on JP2

Aggregatibacter (Actinobacillus) actimycetemcomitans (Aa) is a gram-negative bacterium that colonizes the human oral cavity and is causative agent for localized aggressive (juvenile) periodontitis (AgP). In the middle of 1990s, a specific JP2 clone of belonging to the cluster of serotype b strains of Aa with highly leukotoxicity (leukotoxin, LtxA) able to kill human immune cells was isolated. JP2 clone of Aa was strongly associated with in particularly in rapidly progressing forms of aggressive periodontitis. The JP2 clone of Aa is transmitted through close contacts. Therefore, AgP patients need intense monitoring of their periodontal status as the risk for developing severely progressing periodontitis lesions are relatively high. Furthermore, timely periodontal treatment, including periodontal surgery supplemented by the use of antibiotics, is warranted. More importantly, periodontal attachment loss should be prevented by early detection of the JP2 clone of Aa by microbial diagnosis testing and/or preventive means.

Non-Surgical Therapy Reduces Presence of JP2 Clone in Localized Aggressive Periodontitis

BACKGROUND

Previous studies have provided substantial evidence of the association of Aggregatibacter actinomycetemcomitans, and its highly leukotoxic JP2 genotype, with localized aggressive periodontitis (LAgP). The present study aims to evaluate presence of JP2 in individuals with LAgP after periodontal treatment.

METHODS

Sixty African-American patients with LAgP, aged 5 to 25 years, were examined. At baseline, probing depth (PD), clinical attachment level (CAL), bleeding on probing, and plaque index were measured, and subgingival plaque was collected from LAgP diseased and healthy sites for each participant. Patients received whole-mouth ultrasonic debridement, scaling and root planing, and a 7-day prescription of amoxicillin and metronidazole. Participants were reevaluated and resampled and received regular maintenance therapy at 3, 6, and 12 months after treatment. Polymerase chain reaction was used to detect presence of the JP2 genotype before and after treatment.

RESULTS

At baseline, the JP2 sequence was identified in 75% of LAgP diseased sites and in 56.67% of healthy sites. At 3, 6, and 12 months after treatment, the number of patients was 40, 31, and 31, respectively, and JP2 detection decreased to 17.5%, 6.45%, and 3.23%, respectively, in diseased sites (P <0.001) and to 2.5%, 3.23%, and 0%, respectively, in healthy sites (P <0.001). Clinical parameters of disease were also significantly reduced after therapy (P <0.001). Additionally, significant correlations were observed between JP2 presence and mean PD (P <0.002) and CAL (P <0.001), after therapy.

CONCLUSION

Periodontal therapy was successful in reducing clinical parameters of LAgP and subgingival presence of JP2 in diseased and healthy sites.

Oral microbe-host interactions: influence of β-glucans on gene expression of inflammatory cytokines and metabolome profile

Background

The aim of this study was to evaluate the effects of β-glucan on the expression of inflammatory mediators and metabolomic profile of oral cells [keratinocytes (OBA-9) and fibroblasts (HGF-1) in a dual-chamber model] infected by Aggregatibacter actinomycetemcomitans. The periodontopathogen was applied and allowed to cross the top layer of cells (OBA-9) to reach the bottom layer of cells (HGF-1) and induce the synthesis of immune factors and cytokines in the host cells. β-glucan (10 μg/mL or 20 μg/mL) were added, and the transcriptional factors and metabolites produced were quantified in the remaining cell layers and supernatant.

Results

The relative expression of interleukin (IL)-1-α and IL-18 genes in HGF-1 decreased with 10 μg/mL or 20 μg/mL of β-glucan, where as the expression of PTGS-2 decreased only with 10 μg/mL. The expression of IL-1-α increased with 20 μg/mL and that of IL-18 increased with 10 μg/mL in OBA-9; the expression of BCL 2, EP 300, and PTGS-2 decreased with the higher dose of β-glucan. The production of the metabolite 4-aminobutyric acid presented lower concentrations under 20 μg/mL, whereas the concentrations of 2-deoxytetronic acid NIST and oxalic acid decreased at both concentrations used. Acetophenone, benzoic acid, and pinitol presented reduced concentrations only when treated with 10 μg/mL of β-glucan.

Conclusions

Treatment with β-glucans positively modulated the immune response and production of metabolites.

Profound Effects of Aggregatibacter actinomycetemcomitans Leukotoxin Mutation on Adherence Properties Are Clarified in in vitro Experiments

Leukotoxin (Ltx) is a prominent virulence factor produced by Aggregatibacter actinomycetemcomitans, an oral microorganism highly associated with aggressive periodontitis. Ltx compromises host responsiveness by altering the viability of neutrophils, lymphocytes, and macrophages. Previously, we developed a Rhesus (Rh) monkey colonization model designed to determine the effect of virulence gene mutations on colonization of A. actinomycetemcomitans. Unexpectedly, an A. actinomycetemcomitans leukotoxin (ltxA) mutant (RhAa-VS2) failed to colonize in the Rh model. No previous literature suggested that Ltx was associated with A. actinomycetemcomitans binding to tooth surfaces. These results led us to explore the broad effects of the ltxA mutation in vitro. Results indicated that LtxA activity was completely abolished in RhAa-VS2 strain, while complementation significantly (P<0.0001) restored leukotoxicity compared to RhAa-VS2 strain. RT-PCR analysis of ltx gene expression ruled out polar effects. Furthermore, binding of RhAa-VS2 to salivary-coated hydroxyapatite (SHA) was significantly decreased (P<0.0001) compared to wild type RhAa3 strain. Real time RT-PCR analysis of the genes related to SHA binding in RhAa-VS2 showed that genes related to binding were downregulated [rcpA (P = 0.018), rcpB (P = 0.02), tadA (P = 0.002)] as compared to wild type RhAa3. RhAa-VS2 also exhibited decreased biofilm depth (P = 0.008) and exo-polysaccharide production (P<0.0001). Buccal epithelial cell (BEC) binding of RhAa-VS2 was unaffected. Complementation with ltxA restored binding to SHA (P<0.002) but had no effect on biofilm formation when compared to RhAa3. In conclusion, mutation of ltxA diminished hard tissue binding in vitro, which helps explain the previous in vivo failure of a ltxA knockout to colonize the Rh oral cavity. These results suggest that; 1) one specific gene knockout (in this case ltxA) could affect other seemingly unrelated genes (such as rcpA, rcpB tadA etc), and 2) some caution should be used when interpreting the effect attributed to targeted gene mutations when seen in a competitive in vivo environment.

Pathogenicity of the highly leukotoxic JP2 clone of Aggregatibacter actinomycetemcomitans and its geographic dissemination and role in aggressive periodontitis

For decades, Aggregatibacter actinomycetemcomitans has been associated with aggressive forms of periodontitis in adolescents. In the middle of the 1990s, a specific JP2 clone of A. actinomycetemcomitans, belonging to the cluster of serotype b strains of A. actinomycetemcomitans and having a number of other characteristics, was found to be strongly associated with aggressive forms of periodontitis, particularly in North Africa. Although several longitudinal studies still point to the bacterial species, A. actinomycetemcomitans as a risk factor of aggressive periodontitis, it is now also widely accepted that the highly leukotoxic JP2 clone of A. actinomycetemcomitans is implicated in rapidly progressing forms of aggressive periodontitis. The JP2 clone strains are highly prevalent in human populations living in Northern and Western parts of Africa. These strains are also prevalent in geographically widespread populations that have originated from the Northwest Africa. Only sporadic signs of a dissemination of the JP2 clone strains to non-African populations have been found despite Africans living geographically widespread for hundreds of years. It remains an unanswered question if a particular host tropism exists as a possible explanation for the frequent colonization of the Northwest African population with the JP2 clone. Two exotoxins of A. actinomycetemcomitans are known, leukotoxin (LtxA) and cytolethal distending toxin (Cdt). LtxA is able to kill human immune cells, and Cdt can block cell cycle progression in eukaryotic cells and thus induce cell cycle arrest. Whereas the leukotoxin production is enhanced in JP2 clone strains thus increasing the virulence potential of A. actinomycetemcomitans, it has not been possible so far to demonstrate such a role for Cdt. Lines of evidence have led to the understanding of the highly leukotoxic JP2 clone of A. actinomycetemcomitans as an aetiological factor of aggressive periodontitis. Patients, who are colonized with the JP2 clone, are likely to share this clone with several family members because the clone is transmitted through close contacts. This is a challenge to the clinicians. The patients need intense monitoring of their periodontal status as the risk for developing severely progressing periodontal lesions are relatively high. Furthermore, timely periodontal treatment, in some cases including periodontal surgery supplemented by the use of antibiotics, is warranted. Preferably, periodontal attachment loss should be prevented by early detection of the JP2 clone of A. actinomycetemcomitans by microbial diagnostic testing and/or by preventive means.

Prevalence and distribution of Aggregatibacter actinomycetemcomitans and its cdtB gene in subgingival plaque of Chinese periodontitis patients

BACKGROUND

Aggregatibacter actinomycetemcomitans (A.actinomycetemcomitans) is an important periodontal pathogen that can participate in periodontitis and other non-oral infections. The cytolethal distending toxin (Cdt) is among the virulence factors produced by this bacterium. This study was to elucidate the distribution of A.actinomycetemcomitans and the prevalence of its cdtB gene in Chinese subjects.

METHODS

A total of 255 subgingival samples were obtained from 30 subjects. Samples were collected from periodontal healthy sites as well as shallow, moderate and deep pockets. The absolute quantity of A.actinomycetemcomitans and cdtB gene were determined by real-time polymerase chain reaction.

RESULTS

A.actinomycetemcomitans was detected in 92 of 105 (87.6%) samples of aggressive periodontitis (AgP) patients, in 73 of 79 (92.4%) samples of chronic periodontitis ( CP) patients and in 5 of 71 (7.0%) samples of periodontal healthy subjects. The cdtB gene was detected in 72 sites (78.3%) with AgP infected with A.actinomycetemcomitans, 54 sites (74.0%) with CP infected with A.actinomycetemcomitans and none in healthy sites infected with A.actinomycetemcomitans. In addition, quantity of A.actinomycetemcomitans and cdt gene in samples from deep pockets were significant larger than moderate, shallow and healthy sites (P < 0.05). In comparison to CP, AgP patients were infected with increased numbers of cdt genotype in deep pockets (P < 0.05).

CONCLUSION

This study suggests that the cdtB gene are prevalent in A.actinomycetemcomitans, and the distribution of cdt genotype strain may be correlated with AgP and serious periodontal inflammation.

Leukotoxicity of Aggregatibacter actinomycetemcomitans in generalized aggressive periodontitis in Brazilians and their family members

OBJECTIVE

The purpose of this study was to examine the leukotoxin promoter types of Aggregatibacter actinomycetemcomitans clones in subjects with generalized aggressive periodontitis (GAgP) and in their family members (FM).

MATERIAL AND METHODS

Thirty-five patients with GAgP (33.9±7.1 years), 33 of their FM (22.8±11.4 years), and 41 patients with chronic periodontitis (CP) (44.1±9.4 years) were clinically analyzed using the plaque index, gingival index, probing depth (PD), and clinical attachment level (CAL). Subgingival biofilm samples were collected from four interproximal periodontal sites (>PD and >CAL) of each patient. The presence of A. actinomycetemcomitans and its leukotoxic clone was confirmed by polymerase chain reaction (PCR).

RESULTS

A. actinomycetemcomitans was observed in 23 (51.1%) GAgP patients and 16 (30.1%) CP patients. Thirty-seven (94.8%) patients showed minimally leukotoxic strains and 2 (5.1%) showed highly leukotoxic strains. In the FM group, 10 (30.3%) had aggressive periodontitis (AgP), 12 (36.3%) had CP, 11 (33.3%) were periodontally healthy or had gingivitis, and 12.2% were A. actinomycetemcomitans positive. Greater full mouth PD and CAL were observed in GAgP patients positive for the bacteria than those negative for it (p<;0.05), and the presence of A. actinomycetemcomitans positively correlated with GAgP (Odds ratio, 3.1; confidence interval, 1.4-7.0; p=0.009).

CONCLUSIONS

The presence of A. actinomycetemcomitans was associated with the clinical condition of GAgP, with most patients exhibiting a generalized form of the disease and minimally leukotoxic clones. Most of the relatives of GAgP patients presented either CP or AgP.

Antibiotic susceptibility of Aggregatibacter actinomycetemcomitans JP2 in a biofilm

BACKGROUND

Localized aggressive periodontitis (LAgP) is an inflammatory disease associated with specific bacteria, particularly Aggregatibacter actinomycetemcomitans, which can result in early tooth loss. The bacteria grow as a biofilm known as subgingival plaque. Treatment includes mechanical debridement of the biofilm, often associated with empirical antibiotic treatment.

OBJECTIVE

The aims of this study were to test in vitro the sensitivity of A. actinomycetemcomitans JP2 during planktonic and biofilm growth to doxycycline and to the combination of metronidazole and amoxicillin, which are two antibiotic protocols commonly used in clinical practice.

DESIGN

Two in vitro biofilm models were used to test the effects of the antibiotics: a static 96-well plate assay was used to investigate the effect of these antibiotics on biofilm formation whilst a flow chamber model was used to examine the effect on established biofilms.

RESULTS

Of the antibiotics tested in this model system, doxycycline was most efficacious with a minimal inhibitory concentration (MIC) against planktonic cells of 0.21 mg/L and minimal biofilm inhibitory concentration (MBIC) of 2.10 mg/L. The most commonly prescribed antibiotic regimen, amoxicillin + metronidazole, was much less effective against both planktonic and biofilm cells with an MIC and MBIC of 12.0 mg/L and 20.2 mg/L, respectively. A single treatment of the clinically achievable concentration of 10 mg/L doxycycline to sparse A. actinomycetemcomitans biofilms in the flow chamber model resulted in significant decreases in biofilm thickness, biovolume, and cell viability. Dense A. actinomycetemcomitans biofilms were significantly more resistant to doxycycline treatment. Low concentrations of antibiotics enhanced biofilm formation.

CONCLUSION

A. actinomycetemcomitans JP2 homotypic biofilms were more susceptible in vitro to doxycycline than amoxicillin + metronidazole.

Quantitative discrimination of Aggregatibacter actinomycetemcomitans highly leukotoxic JP2 clone from non-JP2 clones in diagnosis of aggressive periodontitis

BACKGROUND

Aggregatibacter actinomycetemcomitans is the etiological agent of periodontitis, and there is a strong association between clone JP2 and aggressive periodontitis in adolescents of African descent. The JP2 clone has an approximately 530-bp deletion (∆530) in the promoter region of the lkt/ltx gene, which encodes leukotoxin, and this clone has high leukotoxic activity. Therefore, this clone is very important in aggressive periodontitis. To diagnose this disease, culture methods and conventional PCR techniques are used. However, quantitative detection based on qPCR for the JP2 clone has not been developed due to genetic difficulties. In this study, we developed a qPCR-based quantification method specific to the JP2 clone.

METHODS

Based on our analysis of the DNA sequence of the lkt/ltx gene and its flanking region, we designed a reverse primer specific for the ∆530 deletion border sequence and developed a JP2-specific PCR-based quantification method using this primer. We also analyzed the DNA sequence of the ∆530 locus and found it to be highly conserved (97-100%) among 17 non-JP2 strains. Using the ∆530 locus, we designed a qPCR primer-probe set specific to non-JP2 clones. Next, we determined the numbers of JP2 and non-JP2 clone cells in the periodontal pockets of patients with aggressive periodontitis.

RESULTS

The JP2-specific primers specifically amplified the genomic DNA of the A. actinomycetemcomitans JP2 clone and did not react with other bacterial DNA, whereas the non-JP2 specific primers reacted only with A. actinomycetemcomitans non-JP2 clones. Samples from the 88 periodontal sites in the 11 patients with aggressive periodontitis were analyzed. The bacterial cell numbers in 88 periodontal sites ranged from 0 to 4.8 × 10(8) (mean 1.28 × 10(7)) for JP2 clones and from 0 to 1.6 × 10(6) for non-JP2 clones (mean 1.84 × 10(5)). There were significant differences in the JP2 cell number between a clinical attachment level (CAL) ≤6 mm and a level ≥7 mm (p < 0.01). Our new qPCR-based JP2- and non-JP2-specific quantitative detection assay is applicable to the diagnosis of aggressive periodontitis with A. actinomycetemcomitans.

CONCLUSIONS

We successfully developed a quantitative and discriminative PCR-based method for the detection of A. actinomycetemcomitans JP2 and non-JP2 clones. This technique will contribute to future analyses of the quantitative relationship between this organism and aggressive periodontitis.

The highly leukotoxic JP2 clone of Aggregatibacter actinomycetemcomitans in localized and generalized forms of aggressive periodontitis

OBJECTIVE

To investigate the presence of A. actinomycetemcomitans, including the highly virulent JP2 clone, in young adult patients with aggressive periodontitis, and associate the findings with the two forms of the disease.

MATERIALS AND METHODS

Seventy Moroccan subjects with aggressive periodontitis, aged less than 35 years, were recruited. Among these, 41 had LAgP and 29 had GAgP. Plaque samples were collected from periodontal pockets and examined using a PCR that detects the presence of A. actinomycetemcomitans and which differentiates between JP2 and non-JP2 genotypes of the bacterium.

RESULTS

total of 58 (83%) from the 70 AgP patients were positive for A. actinomycetemcomitans, among whom 77% were positives for the JP2 clone. The JP2 clone was detected in 34 (83%) of the LAgP patients compared to 20 (69%) of the GAgP patients (p = 0.17). Fourteen (20%) of the patients harbored non-JP2 genotypes of A. actinomycetemcomitans, although most of these patients (10/14) also harbored the JP2 clone.

CONCLUSIONS

The presence of the JP2 clone of A. actinomycetemcomitans is strongly associated with both LAgP and GAgP in young adults in Morocco. This implies that treatment of AgP in this population should include microbiological screening and aim at eradication of the bacterium when present.

The clinical effect of scaling and root planing and the concomitant administration of systemic amoxicillin and metronidazole: a systematic review

BACKGROUND

The treatment of periodontitis frequently begins with a non-surgical phase that includes scaling and root planing (SRP) and, on occasion, the use of systemic antibiotics. The goal of this review is to systematically evaluate the data concerning the effect of the concomitant administration of amoxicillin and metronidazole adjunctive to SRP in adults who are otherwise healthy.

METHODS

The PubMed-MEDLINE, Cochrane-Central, and EMBASE databases were searched to April 1, 2012, to identify appropriate studies. Probing depth (PD), clinical attachment level (CAL), bleeding on probing, and plaque index were selected as outcome variables. Based on the extracted mean values and number of individuals, changes in weighted means were calculated and a meta-analysis conducted.

RESULTS

The search yielded 526 unique titles and abstracts. Ultimately, 35 studies were selected, describing 28 clinical trials meeting the eligibility criteria. The full-mouth weighted mean change for PD showed an improvement of 1.41 mm. The full-mouth weighted mean change for CAL showed a gain of 0.94 mm.

CONCLUSION

Systemic antimicrobial therapy using a combination of amoxicillin and metronidazole as an adjunct to SRP can enhance the clinical benefits of non-surgical periodontal therapy in adults who are otherwise healthy.

In vitro efficacy of diallyl sulfides against the periodontopathogen Aggregatibacter actinomycetemcomitans

The in vitro antibacterial effects of diallyl sulfide (DAS) against the Gram-negative periodontopathogen Aggregatibacter actinomycetemcomitans, the key etiologic agent of the severe form of localized aggressive periodontitis and other nonoral infections, were studied. A. actinomycetemcomitans was treated with garlic extract, allicin, or DAS, and the anti-A. actinomycetemcomitans effects of the treatment were evaluated. Garlic extract, allicin, and DAS significantly inhibited the growth of A. actinomycetemcomitans (greater than 3 log; P < 0.01) compared to control cells. Heat inactivation of the garlic extracts significantly reduced the protein concentration; however, the antimicrobial effect was retained. Purified proteins from garlic extract did not exhibit antimicrobial activity. Allicin lost all its antimicrobial effect when it was subjected to heat treatment, whereas DAS demonstrated an antimicrobial effect similar to that of the garlic extract, suggesting that the antimicrobial activity of garlic extract is mainly due to DAS. An A. actinomycetemcomitans biofilm-killing assay performed with DAS showed a significant reduction in biofilm cell numbers, as evidenced by both confocal microscopy and culture. Scanning electron microscopy (SEM) analysis of DAS-treated A. actinomycetemcomitans biofilms showed alterations of colony architecture indicating severe stress. Flow cytometry analysis of OBA9 cells did not demonstrate apoptosis or cell cycle arrest at therapeutic concentrations of DAS (0.01 and 0.1 μg/ml). DAS-treated A. actinomycetemcomitans cells demonstrated complete inhibition of glutathione (GSH) S-transferase (GST) activity. However, OBA9 cells, when exposed to DAS at similar concentrations, showed no significant differences in GST activity, suggesting that DAS-induced GST inhibition might be involved in A. actinomycetemcomitans cell death. These findings demonstrate that DAS exhibits significant antibacterial activity against A. actinomycetemcomitans and that this property might be utilized for exploring its therapeutic potential in treatment of A. actinomycetemcomitans-associated oral and nonoral infections.

Effects of low-dose doxycycline on cytokine secretion in human monocytes stimulated with Aggregatibacter actinomycetemcomitans

Doxycycline is an antibiotic used in the treatment of a variety of inflammatory conditions, including periodontitis. Apart from its antimicrobial properties, this drug also has independent anti-inflammatory effects at sub-antimicrobial doses. The present study aimed to investigate the effects of low-doses of doxycycline (LDD) on cytokine production by human monocytic cells challenged with the periodontal pathogen Aggregatibacter actinomycetemcomitans, for up to 6 h. The simultaneous regulation of 12 cytokines were measured by a Human Cytokine Array Kit. To validate the array findings, selected cytokines were also measured by enzyme-linked immunosorbant assay (ELISA). A. actinomycetemcomitans stimulated the production of tumor necrosis factor (TNF)-α, interleukin (IL)-1α, IL-1β, IL-6 and IL-8 by the cells after 6 h of challenge, and doxycycline significantly inhibited this effect. The kinetics of this regulation demonstrated an early (within 2 h) and significant (P<0.05) inhibition of pro-inflammatory cytokines, with a mild (0.5-fold) up-regulation of the anti-inflammatory cytokine IL-10. The results indicate that LDD acts as an anti-inflammatory agent in human monocytic cells stimulated with A. actinomycetemcomitans. This model provides clear evidence that some of the clinically proven benefits of LDD may be related to its ability to regulate inflammatory mediator release by monocytic cells. This property may contribute to the clinically proven benefits of this antibiotic as an adjunctive treatment for periodontitis.

Microbiological and immunological characteristics of young Moroccan patients with aggressive periodontitis with and without detectable Aggregatibacter actinomycetemcomitans JP2 infection

Cross-sectional and longitudinal studies identify the JP2 clone of Aggregatibacter actinomycetemcomitans as an aetiological agent of aggressive periodontitis (AgP) in adolescents of northwest African descent. To gain information on why a significant part of Moroccan adolescents show clinical signs of periodontal disease in the absence of this pathogen we performed comprehensive mapping of the subgingival microbiota of eight young Moroccans, four of whom were diagnosed with clinical signs of AgP. The analysis was carried out by sequencing and phylogenetic analysis of a total of 2717 cloned polymerase chain reaction amplicons of the phylogenetically informative 16S ribosomal RNA gene. The analyses revealed a total of 173 bacterial taxa of which 39% were previously undetected. The JP2 clone constituted a minor proportion of the complex subgingival microbiota in patients with active disease. Rather than identifying alternative aetiologies to AgP, the recorded infection history of the subjects combined with remarkably high concentrations of antibodies against the A. actinomycetemcomitans leukotoxin suggest that disease activity was terminated in some patients with AgP as a result of elimination of the JP2 clone. This study provides information on the microbial context of the JP2 clone activity in a JP2-susceptible population and suggests that such individuals may develop immunity to AgP.

Short-term benefits of the adjunctive use of metronidazole plus amoxicillin in the microbial profile and in the clinical parameters of subjects with generalized aggressive periodontitis

AIM

The aim of this study was to evaluate the clinical and microbiological effects of scaling and root planing (SRP) alone or combined with metronidazole (MTZ) and amoxicillin (AMX) in the treatment of subjects with generalized aggressive periodontitis (GAgP).

MATERIALS AND METHODS

A double-blind, placebo-controlled, randomized clinical trial was conducted in 30 subjects receiving SRP alone or combined with MTZ (400 mg 3 x per day) and AMX (500 mg 3 x per day) for 14 days. Clinical and microbiological examinations were performed at baseline and 3 months post-SRP. Nine subgingival plaque samples per subject were analysed using checkerboard DNA-DNA hybridization.

RESULTS

Subjects receiving MTZ and AMX showed the greatest improvements in the mean full-mouth probing depth and clinical attachment level and at initially intermediate and deep sites. The most beneficial changes in the microbial profile were also observed in the MTZ+AMX group, which showed the lowest proportions of the red complex as well as a significant decrease in the proportions of the orange complex after treatment. The antibiotic therapy also reduced the levels of Aggregatibacter actinomycetemcomitans at initially deep sites.

CONCLUSION

Subjects with GAgP significantly benefit from the adjunctive use of MTZ and AMX. The short-term advantages are observed in the clinical and microbiological parameters.