Carriage of the JP2 Genotype of Aggregatibacter actinomycetemcomitans by Periodontitis Patients of Various Geographic Origin, Living in Sweden

The JP2 genotype of Aggregatibacter actinomycetemcomitans serotype b is associated with aggressive forms of periodontitis and was initially identified as affecting adolescents in North and West Africa. The dissemination of this genotype follows the migration routes and can today be detected in samples from periodontitis patients in a high number of countries. In the present study, we aim to describe findings of the JP2 genotype A. actinomycetemcomits in a clinical laboratory at the Dental School, Odontology, Umeå University, Sweden. The findings of JP2 carriers are documented during a 21-year period, and the age and geographic origin of the sampled individuals are described. In addition, the collected JP2 isolates were separated into North or West African origin by analyses of the presence of a point mutation in the hbpA2 pseudogene of the bacterium. In a total of 2296 sampled individuals during this period in this Swedish population of periodontitis patients, 32 JP2 carriers were detected by cultivation and PCR. The geographic background of these individuals was diverse, including sixteen with African origin, ten with a Swedish origin and six additional ones with a non-African origin. The JP2 genotypes of A. actinomycetemcomitans were mainly isolated from young individuals (<35 years of age), and seven out of the 32 isolates were of a West African origin based on the sequence of hbpA2. We conclude that the JP2 genotype of A. actinomycetemcomitans can be detected world-wide in subgingival plaque samples from adolescents affected by periodontitis.

Clinical laboratory diagnostics in dentistry: Application of microbiological methods

Diagnosis and treatment in dentistry are based on clinical examination of the patients. Given that the major oral diseases are of microbial biofilm etiology, it can be expected that performing microbiological analysis on samples collected from the patient could deliver supportive evidence to facilitate the decision-making process by the clinician. Applicable microbiological methods range from microscopy, to culture, to molecular techniques, which can be performed easily within dedicated laboratories proximal to the clinics, such as ones in academic dental institutions. Periodontal and endodontic infections, along with odontogenic abscesses, have been identified as conditions in which applied clinical microbiology may be beneficial for the patient. Administration of antimicrobial agents, backed by microbiological analysis, can yield more predictable treatment outcomes in refractory or early-occurring forms of periodontitis. Confirming a sterile root canal using a culture-negative sample during endodontic treatment may ensure the longevity of its outcome and prevent secondary infections. Susceptibility testing of samples obtained from odontogenic abscesses may facilitate the selection of the appropriate antimicrobial treatment to prevent further spread of the infection.

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.

Characterization of Aggregatibacter actinomycetemcomitans Serotype b Strains with Five Different, Including Two Novel, Leukotoxin Promoter Structures

The JP2 genotype of A. actinomycetemcomitans, serotype b has attracted much interest during the past three decades due to its close association with periodontitis in young individuals and the enhanced expression of a leukotoxin (LtxA). A typical feature of this genotype is a 530-base pair (bp) deletion in the ltxCABD promoter region controlling leukotoxin expression. In the present work, we have characterized serotype b strains with four additional promoter types. Two novel types have been recognized, that is, one with a 230-bp deletion and one with a 172-bp duplication. Moreover, a strain with a 640-bp deletion and three strains with a full-length promoter, including the type strain Y4, were included in the present study. The seven strains were characterized by multi locus sequence typing (MLST) and arbitrarily primed polymerase chain reaction (PCR) and assessed for LtxA production. MLST showed that the strains with the non-JP2-like deletions represented distinct monophyletic groups, whereas the JP2 strain, HK1651, represented a separate branch. LtxA production was high in all three strains with a promoter deletion, whereas the other four strains showed significantly lower levels. It can be concluded that the genetic characterization and determination of LtxA production of A. actinomycetemcomitans isolates from individuals with periodontitis can contribute to the identification of novel virulent genotypes of this bacterium.

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.

Virulence and Pathogenicity Properties of Aggregatibacter actinomycetemcomitans

Aggregatibacter actinomycetemcomitans is a periodontal pathogen colonizing the oral cavity of a large proportion of the human population. It is equipped with several potent virulence factors that can cause cell death and induce or evade inflammation. Because of the large genetic diversity within the species, both harmless and highly virulent genotypes of the bacterium have emerged. The oral condition and age, as well as the geographic origin of the individual, influence the risk to be colonized by a virulent genotype of the bacterium. In the present review, the virulence and pathogenicity properties of A. actinomycetemcomitans will be addressed.

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.

Aggregatibacter actinomycetemcomitans serotypes and DGGE subtypes in Thai adults with chronic periodontitis

OBJECTIVE

To investigate the distribution of Aggregatibacter actinomycetemcomitans serotypes and DGGE subtypes among isolates from Thai chronic periodontitis patients.

DESIGN

Forty-four adult Thai periodontitis patients were assessed by a full mouth recording for CAL, PPD, and BOP. Seventy-nine strains of A. actinomycetemcomitans were isolated from deep pockets on selective TSBV agar and 17 strains were isolated from shallow pockets. The strains were serotyped using PCR and subtyped using DGGE.

RESULTS

The prevalence of A. actinomycetemcomitans was 84.1%. Non-serotypeable A. actinomycetemcomitans strains occurred equally frequent as serotypeable (54.5%); serotype a 18.2%, serotype c 15.9%, serotype e 9.1%, and serotype f 11.4%. Serotype b and d were not detected. A JP2 like strain but serotyped as c was isolated from two patients, and another two strains showed an 886bp insertion on the ltx promoter of their A. actinomycetemcomitans isolates. DGGE typing disclosed 16 different subtypes among the non-serotypeable strains. Two of them (NS1 and NS2) were more common (12.7 and 10.1%) among the strains than the other 14 subtypes (˂5.1%). Most patients showed only one subtype (32.4%) but 29.7% had 2 and 3 different subtypes while 8.1% revealed 4 subtypes in one and the same deep pocket.

CONCLUSION

This study showed a greater subtype diversity of A. actinomycetemcomitans predominated by non-serotypeable strains than previously reported in an adult Thai population. It was also revealed for the first time that isolates with a 530bp deletion or 886bp insertion of the ltx promoter were serotyped as serotype c.

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.

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.

Leukotoxic activity of Aggregatibacter actinomycetemcomitans and periodontal attachment loss

Aggregatibacter actinomycetemcomitans is a Gram-negative periodontitis-associated bacterium that expresses a toxin that selectively affects leukocytes. This leukotoxin is encoded by an operon belonging to the core genome of this bacterial species. Variations in the expression of the leukotoxin have been reported, and a well-characterized specific clonal type (JP2) of this bacterium with enhanced leukotoxin expression has been isolated. In particular, the presence of the JP2 genotype significantly increases the risk for the progression of periodontal attachment loss (AL). Based on these findings we hypothesized that variations in the leukotoxicity are linked to disease progression in infected individuals. In the present study, the leukotoxicity of 239 clinical isolates of A. actinomycetemcomitans was analysed with different bioassays, and the genetic peculiarities of the isolates were related to their leukotoxicity based on examination with molecular techniques. The periodontal status of the individuals sampled for the presence of A. actinomycetemcomitans was examined longitudinally, and the importance of the observed variations in leukotoxicity was evaluated in relation to disease progression. Our data show that high leukotoxicity correlates with an enhanced risk for the progression of AL. The JP2 genotype isolates were all highly leukotoxic, while the isolates with an intact leukotoxin promoter (non-JP2 genotypes) showed substantial variation in leukotoxicity. Genetic characterization of the non-JP2 genotype isolates indicated the presence of highly leukotoxic genotypes of serotype b with similarities to the JP2 genotype. Based on these results, we conclude that A. actinomycetemcomitans harbours other highly virulent genotypes besides the previously described JP2 genotype. In addition, the results from the present study further highlight the importance of the leukotoxin as a key virulence factor in aggressive forms of periodontitis.

Evaluation of three selective media for isolation of Aggregatibacter actinomycetemcomitans

BACKGROUND AND OBJECTIVE

Aggregatibacter actinomycetemcomitans is a pathogen in oral and nonoral infections. Detection and quantification of this pathogen can be performed using selective culture techniques. The aim of this study was to establish the efficacy of two known selective media in their ability to select and support the growth of A. actinomycetemcomitans.

MATERIAL AND METHODS

Trypticase soy bacitracin vancomycin (TSBV) medium and brain-heart infusion agar with vancomycin (Dentaid-1), as well as a modified Dentaid-1 medium (in which the brain-heart infusion agar was substituted with brain-heart infusion broth), were compared. Two-hundred and eighteen clinical samples were used to establish the recovery rate, the number of colony-forming units (CFUs) of A. actinomycetemcomitans as well as the total number of CFUs on the three different types of medium. In addition, the numbers of gram-negative aerobic rods and yeasts were determined.

RESULTS

Both types of Dentaid-1 medium showed a higher recovery of A. actinomycetemcomitans compared with TSBV. However, these differences did not reach statistical significance. The total number of CFUs of A. actinomycetemcomitans recovered was significantly higher on Dentaid-1 compared with TSBV (p = 0.029). The mean number of gram-negative aerobic rods recovered was statistically higher on both types of Dentaid-1 medium in comparison with TSBV. Low numbers of yeasts were recovered occasionally on all test plates.

CONCLUSION

Dentaid-1 is a low-cost effective alternative to TSBV for the isolation and growth of A. actinomycetemcomitans from clinical samples, such as dental plaque, which contain a complex microflora.

Interactions of extracts from selected chewing stick sources with Aggregatibacter actinomycetemcomitans

Background

Aggregatibacter actinomycetemcomitans produces a leukotoxin that activates a pro-inflammatory death of human monocytes/macrophages. A specific clone of this bacterium (JP2) has a 530-base pair deletion in the leukotoxin promoter gene and significantly enhanced expression of leukotoxin. This specific clone of A. actinomycetemcomitans is common in some African populations and has a strong association with periodontal attachment loss in adolescents in these populations. Chewing sticks of plant origin are commonly used as oral hygiene tool in Africa, but their role as a therapeutic agent in periodontal disease is poorly investigated.

Results

Ethanol extracts were made from 7 common plants used as chewing sticks in West-Africa. None of the tested extracts inhibited growth of A. actinomycetemcomitans. However, extracts from Psidium guajava (Guava) completely neutralized the cell death and pro-inflammatory response of human leukocytes induced by the leukotoxin. None of the six other tested chewing stick extracts showed this effect.

Conclusions

The discovery that extracts from Guava efficiently neutralizes A. actinomycetemcomitans leukotoxicity might lead to novel therapeutic agents and strategies for prevention and treatment of aggressive forms of periodontitis induced by infections with the highly leukotoxic JP2 clone of this bacterium.

Aggregatibacter actinomycetemcomitans leukotoxin: a powerful tool with capacity to cause imbalance in the host inflammatory response

Aggregatibacter actinomycetemcomitans has been described as a member of the indigenous oral microbiota of humans, and is involved in the pathology of periodontitis and various non-oral infections. This bacterium selectively kills human leukocytes through expression of leukotoxin, a large pore-forming protein that belongs to the Repeat in Toxin (RTX) family. The specificity of the toxin is related to its prerequisite for a specific target cell receptor, LFA-1, which is solely expressed on leukocytes. The leukotoxin causes death of different leukocyte populations in a variety of ways. It activates a rapid release of lysosomal enzymes and MMPs from neutrophils and causes apoptosis in lymphocytes. In the monocytes/macrophages, the toxin activates caspase-1, a cysteine proteinase, which causes a proinflammatory response by the activation and secretion of IL-1β and IL-18. A specific clone (JP2) of A. actinomycetemcomitans with enhanced leukotoxin expression significantly correlates to disease onset in infected individuals. Taken together, the mechanisms by which this toxin kills leukocytes are closely related to the pathogenic mechanisms of inflammatory disorders, such as periodontitis. Therapeutic strategies targeting the cellular and molecular inflammatory host response in periodontal diseases might be a future treatment alternative.