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  • 1
    In: Antibiotics, MDPI AG, Vol. 11, No. 3 ( 2022-02-27), p. 317-
    Kurzfassung: The Aggregatibacter actinomycetemcomitans JP2 genotype is associated with high leukotoxin production and severe (aggressive) periodontitis. The aim of this study was to compare the antimicrobial susceptibility of JP2 and non-JP2 genotype strains. Minimal inhibitory concentrations (MICs) of 11 antimicrobials were determined for 160 A. actinomycetemcomitans of serotype a, b, or c, mostly isolated in Sweden or Ghana. MIC distributions for benzylpenicillin and fusidic acid revealed a more susceptible subpopulation for 38 serotype b strains, including the 32 of the JP2 genotype, with a benzylpenicillin MIC range of 0.125–0.5 mg/L. In contrast, benzylpenicillin MIC ≤ 16 mg/L was the estimated 99.5% epidemiological cutoff (ECOFF) of all strains. Beta-lactamase production was not detected. The fusidic acid MIC distribution of 11 strains of Aggregatibacter aphrophilus agreed with that found in non-JP2 strains. Cefotaxime, meropenem, levofloxacin, and trimethoprim–sulfamethoxazole MICs were all ≤0.25 mg/L, while MIC90 values for amoxicillin, azithromycin and tetracycline were 1 mg/L. Metronidazole MICs varied between 0.5 and 〉 256 mg/L. The discrepant findings indicate that A. actinomycetemcomitans may be divided into two separate wild types, with a suggested intrinsic reduced susceptibility for benzylpenicillin in the majority of non-JP2 genotype strains. Possible implications for the treatment of A. actinomycetemcomitans infections are discussed.
    Materialart: Online-Ressource
    ISSN: 2079-6382
    Sprache: Englisch
    Verlag: MDPI AG
    Publikationsdatum: 2022
    ZDB Id: 2681345-2
    SSG: 15,3
    Standort Signatur Einschränkungen Verfügbarkeit
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  • 2
    In: Vaccines, MDPI AG, Vol. 8, No. 3 ( 2020-07-20), p. 398-
    Kurzfassung: 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.
    Materialart: Online-Ressource
    ISSN: 2076-393X
    Sprache: Englisch
    Verlag: MDPI AG
    Publikationsdatum: 2020
    ZDB Id: 2703319-3
    Standort Signatur Einschränkungen Verfügbarkeit
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  • 3
    In: Microorganisms, MDPI AG, Vol. 10, No. 12 ( 2022-12-19), p. 2511-
    Kurzfassung: The aims of the present study were to document the presence of Aggregatibacter actinomyctemcomitans and the emerging oral pathogen Filifactor alocis, as well as to identify genotypes of these bacterial species with enhanced virulence. In addition, these data were analyzed in relation to periodontal pocket depth (PPD) and the progression of PPD from the sampled periodontal sites during a two-year period. Subgingival plaque samples were collected from 172 periodontal pockets of 68 Ghanaian adolescents. PPD at sampling varied from 3–14 mm and the progression from baseline, i.e., two years earlier up to 8 mm. The levels of A. actinomycetemcomitans and F. alocis were determined with quantitative PCR. The highly leukotoxic JP2-genotype of A. actinomycetemcomitans and the ftxA a gene of F. alocis, encoding a putative Repeats-in-Toxin (RTX) protein, were detected with conventional PCR. The prevalence of A. actinomycetemcomitans was 57%, and 14% of the samples contained the JP2 genotype. F. alocis was detected in 92% of the samples and the ftxA gene in 52%. The levels of these bacterial species were significantly associated with enhanced PPD and progression, with a more pronounced impact in sites positive for the JP2 genotype or the ftxA gene. Taken together, the results indicate that the presence of both A. actinomycetemcomitans and F. alocis with their RTX proteins are linked to increased PPD and progression of disease.
    Materialart: Online-Ressource
    ISSN: 2076-2607
    Sprache: Englisch
    Verlag: MDPI AG
    Publikationsdatum: 2022
    ZDB Id: 2720891-6
    Standort Signatur Einschränkungen Verfügbarkeit
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  • 4
    In: Pathogens, MDPI AG, Vol. 8, No. 3 ( 2019-09-17), p. 153-
    Kurzfassung: The bacterium Aggregatibacter actinomycetemcomitans is associated with aggressive forms of periodontitis and with systemic diseases, such as endocarditis. By assessing a Ghanaian longitudinal adolescent cohort, we earlier recognized the cagE gene as a possible diagnostic marker for a subgroup of JP2 and non-JP2 genotype serotype b A. actinomycetemcomitans strains, associated with high leukotoxicity as determined in a semi-quantitative cell assay. This group of A. actinomycetemcomitans is associated with the progression of attachment loss. In the present work, we used conventional polymerase chain reaction (PCR) and quantitative PCR to perform the cagE genotyping of our collection of 116 selected serotype b A. actinomycetemcomitans strains, collected over a period of 15 years from periodontitis patients living in Sweden. The A. actinomycetemcomitans strains carrying cagE (referred to as cagE+; n = 49) were compared to the cagE-negative strains (n = 67), present at larger proportions in the subgingival plaque samples, and were also much more prevalent in the young (≤35 years) compared to in the old ( 〉 35 years) group of patients. Our present results underline the potential use of cagE genotyping in the risk assessment of the development of periodontal attachment loss in Swedish adolescents.
    Materialart: Online-Ressource
    ISSN: 2076-0817
    Sprache: Englisch
    Verlag: MDPI AG
    Publikationsdatum: 2019
    ZDB Id: 2695572-6
    Standort Signatur Einschränkungen Verfügbarkeit
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  • 5
    In: Atmosphere, MDPI AG, Vol. 10, No. 5 ( 2019-05-14), p. 272-
    Kurzfassung: An ensemble of regional climate change scenarios for the North Sea is validated and analyzed. Five Coupled Model Intercomparison Project Phase 5 (CMIP5) General Circulation Models (GCMs) using three different Representative Concentration Pathways (RCPs) have been downscaled with the coupled atmosphere–ice–ocean model RCA4-NEMO. Validation of sea surface temperature (SST) against different datasets suggests that the model results are well within the spread of observational datasets. The ensemble mean SST with a bias of less than 1 ∘ C is the solution that fits the observations best and underlines the importance of ensemble modeling. The exchange of momentum, heat, and freshwater between atmosphere and ocean in the regional, coupled model compares well with available datasets. The climatological seasonal cycles of these fluxes are within the 95% confidence limits of the datasets. Towards the end of the 21st century the projected North Sea SST increases by 1.5 ∘ C (RCP 2.6), 2 ∘ C (RCP 4.5), and 4 ∘ C (RCP 8.5), respectively. Under this change the North Sea develops a specific pattern of the climate change signal for the air–sea temperature difference and latent heat flux in the RCP 4.5 and 8.5 scenarios. In the RCP 8.5 scenario the amplitude of the spatial heat flux anomaly increases to 5 W/m 2 at the end of the century. Different hypotheses are discussed that could contribute to the spatially non-uniform change in air–sea interaction. The most likely cause for an increased latent heat loss in the central western North Sea is a drier atmosphere towards the end of the century. Drier air in the lee of the British Isles affects the balance of the surface heat budget of the North Sea. This effect is an example of how regional characteristics modulate global climate change. For climate change projections on regional scales it is important to resolve processes and feedbacks at regional scales.
    Materialart: Online-Ressource
    ISSN: 2073-4433
    Sprache: Englisch
    Verlag: MDPI AG
    Publikationsdatum: 2019
    ZDB Id: 2605928-9
    SSG: 23
    Standort Signatur Einschränkungen Verfügbarkeit
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  • 6
    Online-Ressource
    Online-Ressource
    MDPI AG ; 2019
    In:  Journal of Clinical Medicine Vol. 8, No. 7 ( 2019-07-22), p. 1079-
    In: Journal of Clinical Medicine, MDPI AG, Vol. 8, No. 7 ( 2019-07-22), p. 1079-
    Kurzfassung: Periodontitis is an infection-induced inflammatory disease that affects the tooth supporting tissues, i.e., bone and connective tissues. The initiation and progression of this disease depend on dysbiotic ecological changes in the oral microbiome, thereby affecting the severity of disease through multiple immune-inflammatory responses. Aggregatibacter actinomycetemcomitans is a facultative anaerobic Gram-negative bacterium associated with such cellular and molecular mechanisms associated with the pathogenesis of periodontitis. In the present review, we outline virulence mechanisms that help the bacterium to escape the host response. These properties include invasiveness, secretion of exotoxins, serum resistance, and release of outer membrane vesicles. Virulence properties of A. actinomycetemcomitans that can contribute to treatment resistance in the infected individuals and upon translocation to the circulation, also induce pathogenic mechanisms associated with several systemic diseases.
    Materialart: Online-Ressource
    ISSN: 2077-0383
    Sprache: Englisch
    Verlag: MDPI AG
    Publikationsdatum: 2019
    ZDB Id: 2662592-1
    Standort Signatur Einschränkungen Verfügbarkeit
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