Interactions of extracts from selected chewing stick sources with Aggregatibacter 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.

Green Alternatives as Antimicrobial Agents in Mitigating Periodontal Diseases: A Narrative Review

Periodontal diseases and dental caries are the most common infectious oral diseases impacting oral health globally. Oral cavity health is crucial for enhancing life quality since it serves as the entranceway to general health. The oral microbiome and oral infectious diseases are strongly correlated. Gram-negative anaerobic bacteria have been associated with periodontal diseases. Due to the shortcomings of several antimicrobial medications frequently applied in dentistry, the lack of resources in developing countries, the prevalence of oral inflammatory conditions, and the rise in bacterial antibiotic resistance, there is a need for reliable, efficient, and affordable alternative solutions for the prevention and treatment of periodontal diseases. Several accessible chemical agents can alter the oral microbiota, although these substances also have unfavorable symptoms such as vomiting, diarrhea, and tooth discoloration. Natural phytochemicals generated from plants that have historically been used as medicines are categorized as prospective alternatives due to the ongoing quest for substitute products. This review concentrated on phytochemicals or herbal extracts that impact periodontal diseases by decreasing the formation of dental biofilms and plaques, preventing the proliferation of oral pathogens, and inhibiting bacterial adhesion to surfaces. Investigations examining the effectiveness and safety of plant-based medicines have also been presented, including those conducted over the past decade.

Aggregatibacter actinomycetemcomitans and Aggregatibacter aphrophilus in a Kenyan Maasai Adolescent Population and Inhibition of Leukotoxic Activity by Herbal Plants Used as Part of Oral Hygiene Procedures

BACKGROUND

A virulent genotype (JP2) of the periodonto-pathogen, Aggregatibacter actinomycetemcomitans (Aa), is widespread in North and West Africa, while its presence in East Africa has not been thoroughly investigated. This JP2 genotype is associated with periodontitis in adolescents and has a high leukotoxicity. The aim of the study was to examine the prevalence of Aa and its JP2 genotype, the prevalence of the oral, commensal Aggregatibacter aphrophilus in a Maasai adolescent population, and the effect of herbal plants for inhibition of leukotoxicity.

METHODS

A total of 284 adolescents from Maasai Mara, Kenya, underwent an oral examination and microbial sampling. The presence of Aa and A. aphrophilus was analyzed by quantitative PCR and cultivation (the 58 samples collected at the last day of field study). The collected Aa strains were characterized and leukotoxin promoter typed. Additionally, herbal plants commonly used for oral hygiene were assessed for the inhibition of leukotoxicity.

RESULTS AND CONCLUSIONS

The prevalence of Aa in stimulated whole saliva was high (71.8%), with the JP2 genotype detected in one individual, and A. aphrophilus in 99% of the sampled individuals. The commonly used herbal plant, Warburgia ugandensis, inactivated Aa leukotoxicity. The Aa virulence might be reduced through use of W. ugandensis and the high levels of A. aphrophilus.

Prevalence of JP2 and Non-JP2 Genotypes of Aggregatibacter actinomycetemcomitans and Oral Hygiene Practice of Kenyan Adolescents in Maasai Mara

Aggregatibacter actinomycetemcomitans is implicated in the etiology of periodontitis that affects adolescents. The monitoring and mapping of the geographic dissemination pattern of JP2 and non-JP2 genotypes of A. actinomycetemcomitans are of interest. In Africa, the highly leukotoxic JP2 genotype is known to be prevalent, particularly in north-west Africa. The aims of this study were to determine the prevalence of JP2 and non-JP2 genotypes and investigate the oral hygiene practices among adolescents living in Maasai Mara, Kenya. A total of 284 adolescents (mean age: 15.0 yrs; SD 1.1) were interviewed regarding their age, gender, medical history, and oral hygiene practice, and the number of teeth present was recorded. One subgingival pooled plaque sample from all the first molars of each participant was analyzed by conventional PCR. The mean number of permanent teeth present was 27.9 (SD: 2.0; range: 22–32; 95% CI: 27.7–28.1). Sixteen (5.6%) and two (0.7%) adolescents were positive for non-JP2 and JP2 genotypes, respectively. For the vast majority of the adolescents, the use of a toothbrush (99.3%) and toothpaste (80.1%), as well as some kind of toothpick (>60.2%), were part of their oral hygiene practice, with dental floss (0.4%) and/or mouth rinses (0.4%) rarely being used. We have, for the first time, identified Kenyan adolescents colonized with the JP2 genotype. The prevalence of the JP2 genotype of A. actinomycetemcomitans is low, a possible indicator that spreading through human migration from North and West Africa to East Africa is a rare occasion.

Comparison of time-kill assay to evaluate the antimicrobial efficacy of garlic (allium sativum) and guava (psidium guajava) extracts on periodontal pathogens

Background:

The role of Gram-negative anaerobic periodontal pathogens in periodontal diseases has led to the loss of tooth-supporting structures. These diseases can be prevented by the inhibition of bacterial biofilm on the tooth surfaces. Many treatment modalities have been tried to prevent periodontal diseases. With the rise in resistance to synthetic antimicrobials, there is a requirement to develop natural antimicrobials for the control of periodontitis.

Aim:

The aim of the study was to evaluate and compare the efficacy of garlic (Allium sativum) and guava (Psidium guajava) extracts on Porphyromonas gingivalis and Aggregatibacter actinomycetemcomitans using time-kill assay.

Materials and Methods:

Aqueous garlic extract (AGaE), ethanolic garlic extract (EGaE), aqueous guava extract (AGuE), and ethanolic guava extract (EGuE) were prepared. Time-kill assays were performed on P. gingivalis and A. actinomycetemcomitans. The aqueous and ethanolic extracts of guava and garlic were compared to assess the maximum bactericidal potency.

Results:

The comparison of time-kill assay of AGaE and AGuE on P. gingivalis showed a statistically significant difference at 2 h (t = 5.29, P < 0.01), 4 h (t = −4.867, P < 0.01), and 6 h (t = −3.647, P < 0.001). The comparison of time-kill assay of EGaE and EGuE on A. actinomycetemcomitans showed a statistically significant difference at 2 h (t = 4.54, P < 0.01) and highly significant difference at 4 h (t = 6.57, P < 0.001).

Conclusions:

The, judicious use of these phytomedicinal products could be cost-effective and also the adverse effects caused due to the long-term usage of synthetic antimicrobials can be avoided.

Efficacy of Psidium guajava and Allium sativum Extracts as Antimicrobial Agents against Periodontal Pathogens

Background:

The accumulation and maturation of bacterial plaque at the gingival margin is widely recognized as the primary etiological factor in the development of chronic periodontitis. With the rise in bacterial resistance to antibiotics, there is considerable interest in the development of other classes of antimicrobials for the control of infection.

Aim:

The aim of this study was to evaluate the efficacy of Psidium guajava (guava) and Allium sativum (garlic) on Porphyromonas gingivalis and Aggregatibacter actinomycetemcomitans.

Materials and Methods:

Aqueous guava extract (AGvE), ethanolic guava extract (EGvE), aqueous garlic extract (AGE), and ethanolic garlic extract (EGE) were prepared. The inhibitory effects of these extracts for the periodontal pathogens were tested by agar well diffusion method. Minimal inhibitory concentration (MIC) of the aqueous and ethanol extracts of guava and garlic was determined by macrobroth dilution method. Minimum bactericidal concentration (MBC) was done to observe the bactericidal effect of the guava and garlic extracts against the organisms.

Results:

Of the AGE, 25, 50, and 75 μL showed 16, 20, and 25 mm zone of inhibition, respectively, on P. gingivalis. The AGE showed greater bacteriostatic activity against the P. gingivalis with MIC determined at 16.6 μL/mL. MIC determined for AGvE and EGvE was at 75 μL/mL concentration for P. gingivalis, whereas EGvE showed the activity at 75 μL/mL on P. gingivalis. MIC determined for AGvE was at 50 μL/mL, whereas MIC determined for EGvE was at 3.12 μL/mL for A. actinomycetemcomitans.

Conclusion:

P. guajava and A. sativum displayed a significant antibacterial effect. A. sativum was found to be most effective against P. gingivalis, whereas P. guajava showed the highest efficacy on A. actinomycetemcomitans.

Aggregatibacter actinomycetemcomitans leukotoxin: From mechanism to targeted anti-toxin therapeutics

Aggregatibacter actinomycetemcomitans is a Gram-negative bacterium associated with localized aggressive periodontitis, as well as other systemic diseases. This organism produces a number of virulence factors, all of which provide some advantage to the bacterium. Several studies have demonstrated that clinical isolates from diseased patients, particularly those of African descent, frequently belong to specific clones of A. actinomycetemcomitans that produce significantly higher amounts of a protein exotoxin belonging to the repeats-in-toxin (RTX) family, leukotoxin (LtxA), whereas isolates from healthy patients harbor minimally leukotoxic strains. This finding suggests that LtxA might play a key role in A. actinomycetemcomitans pathogenicity. Because of this correlation, much work over the past 30 years has been focused on understanding the mechanisms by which LtxA interacts with and kills host cells. In this article, we review those findings, highlight the remaining open questions, and demonstrate how knowledge of these mechanisms, particularly the toxin's interactions with lymphocyte function-associated antigen-1 (LFA-1) and cholesterol, enables the design of targeted anti-LtxA strategies to prevent/treat disease.

Chemical Composition, Antimicrobial activity, in Vitro Cytotoxicity and Leukotoxin Neutralization of Essential Oil from Origanum vulgare against Aggregatibacter actinomycetemcomitans

In this study, the essential oil of Origanum vulgare was evaluated for putative antibacterial activity against six clinical strains and five reference strains of Aggregatibacter actinomycetemcomitans, in comparison with some antimicrobials. The chemical composition of the essential oil was analyzed, using chromatography (CG) and gas chromatography-mass spectrometry coupled (CG-MS). The major compounds in the oil were Carvacrol (32.36%), α-terpineol (16.70%), p-cymene (16.24%), and Thymol (12.05%). The antimicrobial activity was determined by an agar well diffusion test. A broth microdilution method was used to study the minimal inhibitory concentration (MIC). The minimal bactericidal concentration (MBC) was also determined. The cytotoxicity of the essential oil (IC50) was <125 µg/mL for THP-1 cells, which was high in comparison with different MIC values for the A. actinomycetemcomitans strains. O. vulgare essential oil did not interfere with the neutralizing capacity of Psidium guajava against the A. actinomycetemcomitans leukotoxin. In addition, it was shown that the O. vulgare EO had an antibacterial effect against A. actinomycetemcomitans on a similar level as some tested antimicrobials. In view of these findings, we suggest that O.vulgare EO may be used as an adjuvant for prevention and treatment of periodontal diseases associated to A. actinomycetemcomitans. In addition, it can be used together with the previously tested leukotoxin neutralizing Psidium guajava.

Epigallocatechin gallate inhibits leukotoxin release by Aggregatibacter actinomycetemcomitans by promoting association with the bacterial membrane

The oral pathogen, Aggregatibacter actinomycetemcomitans, produces a number of virulence factors, including a leukotoxin (LtxA), which specifically kills human white blood cells, to provide a colonization advantage to the bacterium. Strains of A. actinomycetemcomitans that produce more LtxA have been more closely linked to disease, indicating that this toxin plays a key role in pathogenesis of the bacterium. Disruption of the activity of LtxA thus represents a promising approach to reducing the pathogenicity of the bacterium. Catechins are polyphenolic molecules derived from plants, which have shown potent antibacterial and antitoxin activities. We have previously shown that galloylated catechins are able to prevent LtxA delivery to host cells by altering the toxin's secondary structure and preventing binding to cholesterol on the host cell membrane. Here, we have investigated how one particular galloylated catechin, epigallocatechin gallate (EGCg), affects A. actinomycetemcomitans growth and toxin secretion. Our results demonstrate that EGCg, at micromolar concentrations, inhibits A. actinomycetemcomitans growth, as has been reported for other bacterial species. At subinhibitory concentrations, EGCg promotes LtxA production, but the toxicity of the bacterial supernatant against human immune cells is reduced. The results of our biophysical studies indicate that this seemingly contradictory result is caused by an EGCg-mediated enhancement of LtxA affinity for the bacterial cell surface. Together, these results demonstrate the potential of EGCg in the treatment of virulent A. actinomycetemcomitans infections.

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.

High salivary levels of JP2 genotype of Aggregatibacter actinomycetemcomitans is associated with clinical attachment loss in Moroccan adolescents

It has previously been shown that the presence of Aggregatibacter actinomycetemcomitans in subgingival plaque is significantly associated with increased risk for clinical attachment loss. The highly leukotoxic JP2 genotype of this bacterium is frequently detected in adolescents with aggressive forms of periodontitis. The aims of the study were to quantify the levels of JP2 and non-JP2 genotypes of A. actinomycetemcomitans in saliva of Moroccan adolescents with the JP2 genotype earlier detected in the subgingival plaque. The salivary concentrations of inflammatory proteins were quantified and linked to the clinical parameters and microbial findings. Finally, a mouth rinse with leukotoxin-neutralizing effect was administrated and its effect on the levels the biomarkers and A. actinomycetemcomitans examined. The study population consisted of 22 adolescents that previously were found to be positive for the JP2 genotype in subgingival plaque. Periodontal registration and sampling of stimulated saliva was performed at baseline. A mouth rinse (active/placebo) was administrated, and saliva sampling repeated after 2 and 4 weeks rinse. The salivary levels of JP2 and non-JP2 were analyzed by quantitative PCR and inflammatory proteins by ELISA. Both the JP2 and the non-JP2 genotype were detected in all individuals with significantly higher levels of the non-JP2. Enhanced levels of the JP2 genotype of A. actinomycetemcomitans was significantly correlated to the presence of attachment loss (≥3 mm). Salivary concentrations of inflammatory biomarkers did not correlate to periodontal condition or levels of A. actinomycetemcomitans. The use of active or placebo leukotoxin-neutralizing mouth rinse did not significantly interfered with the levels of these biomarkers. Saliva is an excellent source for detection of A. actinomycetemcomitans on individual basis, and high levels of the JP2 genotype were significantly associated with the presence of clinical attachment loss.

Health Effects of Psidium guajava L. Leaves: An Overview of the Last Decade

Today, there is increasing interest in discovering new bioactive compounds derived from ethnomedicine. Preparations of guava (Psidium guajava L.) leaves have traditionally been used to manage several diseases. The pharmacological research in vitro as well as in vivo has been widely used to demonstrate the potential of the extracts from the leaves for the co-treatment of different ailments with high prevalence worldwide, upholding the traditional medicine in cases such as diabetes mellitus, cardiovascular diseases, cancer, and parasitic infections. Moreover, the biological activity has been attributed to the bioactive composition of the leaves, to some specific phytochemical subclasses, or even to individual compounds. Phenolic compounds in guava leaves have been credited with regulating blood-glucose levels. Thus, the aim of the present review was to compile results from in vitro and in vivo studies carried out with guava leaves over the last decade, relating the effects to their clinical applications in order to focus further research for finding individual bioactive compounds. Some food applications (guava tea and supplementary feed for aquaculture) and some clinical, in vitro, and in vivo outcomes are also included.

Anti-inflammatory, Antioxidant and Antimicrobial Effects of Artemisinin Extracts from Artemisia annua L

The anti-inflammatory, antioxidant, and antimicrobial properties of artemisinin derived from water, methanol, ethanol, or acetone extracts of Artemisia annua L. were evaluated. All 4 artemisinin-containing extracts had anti-inflammatory effects. Of these, the acetone extract had the greatest inhibitory effect on lipopolysaccharide-induced nitric oxide (NO), prostaglandin E₂ (PGE₂), and proinflammatory cytokine (IL-1β , IL-6, and IL-10) production. Antioxidant activity evaluations revealed that the ethanol extract had the highest free radical scavenging activity, (91.0±3.2%), similar to α-tocopherol (99.9%). The extracts had antimicrobial activity against the periodontopathic microorganisms Aggregatibacter actinomycetemcomitans, Fusobacterium nucleatum subsp. animalis, Fusobacterium nucleatum subsp. polymorphum, and Prevotella intermedia. This study shows that Artemisia annua L. extracts contain anti-inflammatory, antioxidant, and antimicrobial substances and should be considered for use in pharmaceutical products for the treatment of dental diseases.

Psidium guajava: A review on its potential as an adjunct in treating periodontal disease

Plants for thousands of years have been used to enhance health and for medicinal purposes. Psidium guajava is one which has an enormous wealth of medicinal value. It for long has been known for its anti-inflammatory, antimicrobial, antioxidant, antidiarrheal, antimutagenic properties. Despite of its widespread biologic uses there is a dearth of information on its therapeutic effect in the treatment of periodontal disease. Hence, this review is an attempt to highlight the potential of P. guajava in the treatment of periodontal disease. Internet databases PubMed, Google Scholar were searched and the most relevant articles were considered for review.

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.