Aggregatibacter actinomycetemcomitans as the Aetiological Cause of Rheumatoid Arthritis: What Are the Unsolved Puzzles?

Leukotoxin A (LtxA) is the major virulence factor of an oral bacterium known as Aggregatibacter actinomycetemcomitans (Aa). LtxA is associated with elevated levels of anti-citrullinated protein antibodies (ACPA) in rheumatoid arthritis (RA) patients. LtxA targets leukocytes and triggers an influx of extracellular calcium into cytosol. The current proposed model of LtxA-mediated hypercitrullination involves the dysregulated activation of peptidylarginine deiminase (PAD) enzymes to citrullinate proteins, the release of hypercitrullinated proteins through cell death, and the production of autoantigens recognized by ACPA. Although model-based evidence is yet to be established, its interaction with the host’s immune system sparked interest in the role of LtxA in RA. The first part of this review summarizes the current knowledge of Aa and LtxA. The next part highlights the findings of previous studies on the association of Aa or LtxA with RA aetiology. Finally, we discuss the unresolved aspects of the proposed link between LtxA of Aa and RA.

Multilocus Sequence Typing of Aggregatibacter actinomycetemcomitans Competently Depicts the Population Structure of the Species

We developed a multilocus sequence typing scheme (MLST) for Aggregatibacter actinomycetemcomitans based on seven housekeeping genes, adk , atpG , frdB , mdh , pgi , recA , and zwf . A total of 188 strains of seven serotypes were separated into 57 sequence types.

Multilocus Sequence Typing of Non-JP2 Serotype b Aggregatibacter actinomycetemcomitans Strains of Ghanaian and Swedish Origin

Objective and MethodsThe Gram-negative bacterium, Aggregatibacter actinomycetemcomitans is associated with periodontitis affecting young individuals. The geographic dissemination of the highly leukotoxic JP2 genotype of serotype b of this species was previously studied by multilocus sequence typing (MLST). Here, we have used MLST to genetically characterize non-JP2 genotype strains of serotype b, isolated from individuals living in Ghana (n=41), and in Sweden (n=13), respectively.ResultsThe MLST analysis revealed a total of nine sequence types (ST). Both Ghanaian and Swedish isolates were distributed in ST 1-3. ST 5 and 6 were only identified among the Ghanaian strains, whereas ST 4, 7, 8 and 9 were uniquely represented among the Swedish strains. Previously, we characterized these non-JP2 genotype strains of A. actinomycetemcomitans serotype b by arbitrarily-primed (AP)-PCR, which distributed them into three groups, AP-PCR type 1, 2, and 3, respectively. AP-PCR type 1 strains are generally highly leukotoxic, and are associated with progression of periodontal attachment loss. As AP-PCR type 1 includes both JP2 genotype strains and a proportion of non-JP2 genotype strains of serotype b, a straightforward diagnostic procedure has been sought. This has revealed a gene, cagE, which appears to be conserved only in this AP-PCR type. According to our results, MLST was not a highly discriminatory method to identify AP-PCR type 1, as strains of this AP-PCR type could be found within three different ST: ST 2, ST 3 and ST 8.ConclusionAccording to MLST, a geographic dissemination of non-JP2 genotype A. actinomycetemcomitans serotype b appears to exist. However, aiming to identify carriers of AP-PCR type 1, non-JP2 genotype serotype b, PCR with cagE-specific primers is likely the most efficient diagnostic procedure known today.

Porphyromonas gingivalis e Aggregatibacter actinomycetemcomitans em sangue do cordão umbilical e periférico, saliva e colostro de mulheres com gengivite

Este estudo investigou e comparou a presença de Porphyromonas gingivalis (Pg) e Aggregatibacter actinomycetemcomitans (Aa) em amostras biológicas de mulheres que tiveram parto a termo com diagnóstico de gengivite e sem doença periodontal. Exames clínicos orais foram realizados em 48 puérperas, incluindo 28 mulheres com periodonto saudável, 15 com gengivite e 5 com periodontite (que foram excluídas da análise). Sangue do cordão umbilical (CU), sangue periférico (SP), saliva (SA) e colostro (C) foram coletados de mulheres elegíveis após o parto. Foi realizada extração de DNA e em seguida a presença de bactérias foi detectada por PCR com primers específicos. Dados sobre gestações anteriores e atuais e fatores de risco conhecidos foram obtidos dos prontuários médicos dos pacientes. Os dados sociais, demográficos e de higiene bucal foram analisados por entrevista. Os resultados mostraram que todas as SA das participantes com gengivite apresentou Pg e Aa, enquanto a minoria das amostras com periodonto saudável apresentou tais bactérias (P <0,05 para cada uma). 60% das mulheres com gengivite apresentaram Pg nas amostras de sangue (CU e SP, p <0,05) e 46,6% apresentaram no C. Aa não apareceu nas amostras de sangue, mas 46,6% das mulheres com gengivite apresentaram Aa em C. Não houve associação entre dados socioeconômicos e de saúde bucal, detecção de microrganismos e presença da doença. Em conclusão, a gengivite esteve relacionada com a detecção positiva de ambas as bactérias em SA. Mulheres com gengivite apresentaram frequentemente Pg nas amostras sanguíneas. A presença de Pg e Aa em C ocorreu apenas em gestantes com gengivite.

An In-Vitro Study Comparing the Effects of Citrus Lemon Extract on Porphyromonas Gingivalis, Aggregatibacter Actinomycetemcomitans, and Prevotella Intermedia

Plant extracts and phytochemicals having antimicrobial characteristics could be immensely beneficial in medicinal treatments. The present study deals with the effect of Citrus lemon extract over Periodontal pathogens which are primary etiologic factors for periodontal diseases. The current study took into account periodontal pathogens such as Prevotella Intermedia, Aggregatibacter Actinomycetemcomitans, and Porphyromonas Gingivalis. Chlorhexidine is a gold standard antimicrobial agent with a wide antibacterial activity that is commonly used for chemical plaque management. When used for an extended period, however, chlorhexidine is known to stain. As a result, the alternatives are to be explored such as herbal-based agents that can be used regularly. Using the microdilution process and the culture method, the antibacterial effect of citrus lemon extract against periodontal pathogens was assessed using the minimum inhibitory concentration (MIC), minimum bactericidal concentration (MBC), and zone of inhibition (ZOI). According to the findings of this study, citrus lemon extract can be used as a natural supplement for treatment purposes. Keywords: Antimicrobial, Citrus lemon Extract, Chlorhexidine, Periodontal Pathogens.

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.

In Vitro Antibacterial Activity of Myrtus communis L. and Marrubium vulgare L. Leaves against Aggregatibacter actinomycetemcomitans and Eikenella corrodens

Background and Objectives. It has been shown that Myrtus communis and Marrubium vulgare have antibacterial activity against bacterial and fungal strains of different diseases. This study aimed to evaluate in vitro the antibacterial activity of aqueous and methanolic extracts of Myrtus communis and Marrubium vulgare leaves against selected periodontal pathogens. Materials and Methods. Clinical strains of Aggregatibacter actinomycetemcomitans and Eikenella corrodens and two reference strains of A. actinomycetemcomitans were tested. The antibacterial activity of each studied plant extract was evaluated using agar diffusion and broth microdilution assays. Results. Both aqueous and methanolic extracts of M. communis exhibited high antibacterial activity against periodontal pathogens as compared to M. vulgare extracts. At concentrations of 2.5-0.32 mg/disc, inhibition zones of the methanolic extract of M. communis ranged from 19.66 ± 0.57 to 12.33 ± 0.57 mm. The methanolic extract of M. vulgare showed at concentrations of 5-0.63 mg/disc inhibition zones ranging from 15.66 ± 0.57 to 12 ± 0.00 mm. Its aqueous extract at concentration of 0.63 mg/disc showed no antimicrobial activity against the clinical and reference strain of A. actinomycetemcomitans. Conclusion. This study showed that methanolic and aqueous extracts of M. communis and M. vulgare have in vitro an antibacterial activity against periodontal pathogens. They could be use as ingredients of an oral antimicrobial agent for prevention or treatment of periodontal diseases. Further research on isolating the compounds from these plant extracts and their toxicity effect could be conducted.