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Biochemical and Biophysical Research... Dec 2022The cytolethal distending toxins (CDTs) produced by many Gram-negative pathogens are tripartite genotoxins with a single catalytic subunit (CdtB) and two cell-binding...
The cytolethal distending toxins (CDTs) produced by many Gram-negative pathogens are tripartite genotoxins with a single catalytic subunit (CdtB) and two cell-binding subunits (CdtA + CdtC). CDT moves by vesicle carriers from the cell surface to the endosomes and through the Golgi apparatus en route to the endoplasmic reticulum (ER). CdtA dissociates from the rest of the toxin before reaching the Golgi apparatus, and CdtB separates from CdtC in the ER. The free CdtB subunit, which is only active after holotoxin disassembly, then crosses the ER membrane and enters the nucleus where it generates DNA breaks. We hypothesized that the acidified lumen of the endosomes is responsible for separating CdtA from the CdtB/CdtC heterodimer. To test this prediction, possible acid-induced disruptions to the CDT holotoxin were monitored by size exclusion chromatography and surface plasmon resonance. We found that CDT could not efficiently assemble from its individual subunits at the early endosome pH of 6.3. Partial disassembly of the CDT holotoxin also occurred at pH 6.3, with complete separation of CdtA from an intact CdtB/CdtC heterodimer occurring at both pH 6.0 and the late endosome pH of 5.6. Acidification caused the precipitation of CdtA at pH 6.5 and below, but neither CdtB nor CdtC were affected by a pH as low as 5.2. Circular dichroism further showed that the individual CdtB subunit adopts a different secondary structure as compared to its structure in the holotoxin. We conclude the first stage of CDT disassembly occurs in the early endosomes, where an acid-induced alteration to CdtA releases it from the CdtB/CdtC heterodimer.
Topics: Haemophilus ducreyi; Bacterial Toxins
PubMed: 36332483
DOI: 10.1016/j.bbrc.2022.10.068 -
Molecular Oral Microbiology Jun 2020Aggregatibacter actinomycetemcomitans is a Gram-negative bacterium associated with localized aggressive periodontitis, as well as other systemic diseases. This organism... (Review)
Review
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.
Topics: Aggregatibacter actinomycetemcomitans; Exotoxins; Humans; Lymphocyte Function-Associated Antigen-1; Virulence Factors
PubMed: 32061022
DOI: 10.1111/omi.12284 -
International Journal of Systematic and... Aug 2021Nine strains of a -related bacterium were isolated over a period of 38 years from a laboratory mouse (), seven laboratory rats () and a Syrian hamster () in...
Nine strains of a -related bacterium were isolated over a period of 38 years from a laboratory mouse (), seven laboratory rats () and a Syrian hamster () in Düsseldorf and Heidelberg, Germany. The isolates are genotypically and phenotypically distinct from all previously described species. Sequence analysis of 16S rRNA and gene sequences placed the isolates as a novel lineage within the genus . In addition to the single-gene analysis, the whole genome sequence of the strain 1625/19 revealed distinct genome-to-genome distance values to the other species. The genomic DNA G+C content of strain 1625/19 was 40.8 mol% within the range of . At least six phenotypic characteristics separate the new isolates from the other species, with being the most closely related. In contrast to the latter, the new strains display β-haemolysis and are β-glucuronidase, d-mannitol and sorbitol positive, but fail to produce lysine decarboxylase and trehalose. The genotypic and phenotypic differences between the novel strains and the other closely related strains of the genus indicate that they represent a novel species within the genus , family , for which the name sp. nov. is proposed. The type strain 1625/19, (=DSM 111151=CCM 9081), was isolated in 2019 from the nose of a laboratory mouse () in Düsseldorf, Germany.
Topics: Animals; Animals, Laboratory; Bacterial Typing Techniques; Base Composition; DNA, Bacterial; Fatty Acids; Germany; Mesocricetus; Mice; Pasteurellaceae; Phylogeny; RNA, Ribosomal, 16S; Rats; Sequence Analysis, DNA
PubMed: 34379582
DOI: 10.1099/ijsem.0.004947 -
Veterinary Microbiology Aug 2022The serotypes of Pasteurella multocida were predicted based on whole genomic sequences (WGS) with specific genes of the capsular and liposaccharide (LPS) outer core...
The serotypes of Pasteurella multocida were predicted based on whole genomic sequences (WGS) with specific genes of the capsular and liposaccharide (LPS) outer core polysaccharide regions as targets. A total of 56 strains were whole genomic sequenced and in addition all assembled genomes from NCBI were included for comparison. BIGSdb (Bacterial Isolate Genome Sequence Database) was installed on a Linux server and targets for capsular types A, B, D, E and F were defined as gene sequences of hyaD, bcbD, dcbF, ecbJ and fcbD, respectively and targets for LPS groups 1, 2, 3, 4, 5, 6, 7 and 8 were defined as gene sequences of pcgB, nctA, gatF, latB, rmlA, nctB, ppgB and natG, respectively. The serotypes of P. multocida were predicted from WGS by designating the capsular type and LPS group as well as subtype alleles to isolates. Comparisons between WGS predictions of capsular types and classical phenotypic typing showed correspondence in 87 % of cases whereas comparisons of WGS predictions of LPS groups to phenotypic typing corresponded for 82 % of the strains. In total 93 % and 94 % of the strains available with WGS could be capsular and LPS group typed, respectively. The server is free to access from https://ivsmlst.sund.ku.dk.
Topics: Genome, Bacterial; Genomics; Lipopolysaccharides; Pasteurella multocida; Serogroup
PubMed: 35714528
DOI: 10.1016/j.vetmic.2022.109492 -
Journal of Medical Virology Jan 2023Combination vaccines can reduce the vaccination visit, simplify the vaccination schedule and efficiently improve management. This study was primarily designed to...
Combination vaccines can reduce the vaccination visit, simplify the vaccination schedule and efficiently improve management. This study was primarily designed to evaluate the economic impact of integrating the diphtheria-tetanus-acellular pertussis inactivated poliomyelitis and Haemophilus influenzae type B (DTaP-IPV-Hib) combination vaccine into the China National Immunization Program. A cost-minimization analysis (CMA) compared the costs associated with direct medical, direct nonmedical, and indirect social costs in four schemes was conducted. A budgetary impact analysis assessed the alternative schemes' financial impact on the healthcare budget. Direct medical costs were extracted using a costing questionnaire and an observational time and motion chart. Direct nonmedical (cost for transportation) and indirect costs (loss of productivity) were derived from parents' questionnaires. Replacement of the current vaccination scheme with DTaP-IPV-Hib combination vaccine, resulted in net increases in direct medical costs of 77.64% for alternative scheme 1, 146.54% for alternative scheme 2, and 294.67% for alternative scheme 3, respectively. However, the direct nonmedical and indirect costs and the cost of the alternative schemes were 18.18%, 36.36%, and 63.64% lower than the current scheme for alternative scheme 1, alternative scheme 2, and alternative scheme 3, respectively. From the societal perspective, when compared with the current scheme, the budgetary impact of the three alternative schemes were +66 million Chinese Yuan (CNY) (4.81%), +103 million CNY (7.53%), and +305million CNY (22.35%), respectively. The CMA considered a broader perspective of social costs and indicated that the alternative schemes would result in an overall saving of parents' transportation and work loss costs to bring their children for vaccination, translating into a total cost saving of 18.18%, 36.36%, 63.64%, comparing to the current scheme. Thus, fully or partly using the DTaP-IPV-Hib combination vaccine is cost-saving in the context of China.
Topics: Child; Humans; Infant; Haemophilus influenzae type b; Cross-Sectional Studies; Vaccines, Combined; Costs and Cost Analysis; China
PubMed: 36448181
DOI: 10.1002/jmv.28358 -
The Veterinary Clinics of North... Jul 2020Calves vary considerably in their pathologic and clinical responses to infection of the lung with bacteria. The reasons may include resistance to infection because of... (Review)
Review
Calves vary considerably in their pathologic and clinical responses to infection of the lung with bacteria. The reasons may include resistance to infection because of pre-existing immunity, development of effective immune responses, or infection with a minimally virulent bacterial strain. However, studies of natural disease and of experimental infections indicate that some calves develop only mild lung lesions and minimal clinical signs despite substantial numbers of pathogenic bacteria in the lung. This may represent "tolerance" to pulmonary infection because these calves are able to control their inflammatory responses or protect the lung from damage, without necessarily eliminating bacterial infection. Conversely, risk factors might predispose to bovine respiratory disease by triggering a loss of tolerance that results in a harmful inflammatory and tissue-damaging response to infection.
Topics: Animals; Bovine Respiratory Disease Complex; Cattle; Mannheimia haemolytica
PubMed: 32451029
DOI: 10.1016/j.cvfa.2020.03.003 -
Archives of Oral Biology Aug 2020This 6-year study evaluatedAggregatibacter actinomycetemcomitans outcomes and their relationship to clinical status. (Review)
Review
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.
Topics: Adult; Aged; Aggregatibacter actinomycetemcomitans; Humans; Middle Aged; Pasteurellaceae Infections; Periodontics; Porphyromonas gingivalis; Serogroup; Tannerella forsythia; Treponema denticola; Young Adult
PubMed: 32422332
DOI: 10.1016/j.archoralbio.2020.104747 -
Current Opinion in Infectious Diseases Jun 2020The human upper respiratory tract is colonized with a variety of bacterial microorganisms including Haemophilus influenzae. The species H. influenzae consists of... (Review)
Review
PURPOSE OF REVIEW
The human upper respiratory tract is colonized with a variety of bacterial microorganisms including Haemophilus influenzae. The species H. influenzae consists of typeable and nontypeable H. influenzae (NTHi) variants. Typeable H. influenzae are subdivided into types a through f, based on the polysaccharide capsule, whereas the NTHi strains do not express a polysaccharide capsule. In this review, we highlight the current advances in the field of H. influenzae, with the focus on bacterial virulence mechanisms that facilitate bacterial colonization and disease, particularly for NTHi.
RECENT FINDINGS
In the past decade, it has become apparent that NTHi has the ability to cause invasive infections. Recently, a number of adhesins have been shown to be crucial for bacterial colonization and invasion and these proteins were investigated as vaccine antigens. Although NTHi lacks a polysaccharide capsule, it expresses lipooligosaccharide that contribute to adhesion and evasion of complement-mediated killing, both contributing to bacterial virulence, which could potentially be targeted by novel antimicrobial drugs or vaccines.
SUMMARY
The unraveling of H. influenzae virulence mechanisms resulted in the identification of promising targets for novel antimicrobials and vaccine antigens aiming to prevent or treat both typeable and nontypeable H. influenzae infections.
Topics: Anti-Infective Agents; Haemophilus Infections; Haemophilus Vaccines; Haemophilus influenzae; Humans; Lipopolysaccharides; Virulence
PubMed: 32304471
DOI: 10.1097/QCO.0000000000000645 -
Journal of Veterinary Internal Medicine May 2021Nicoletella semolina was identified in the airways of horses and its low prevalence could be because of its difficult differentiation from other Pasteurellaceae.
BACKGROUND
Nicoletella semolina was identified in the airways of horses and its low prevalence could be because of its difficult differentiation from other Pasteurellaceae.
OBJECTIVES
To develop a molecular method for the identification of N. semolina and to evaluate its prevalence in the mouth and the airways of healthy and severe asthmatic horses.
ANIMALS
Six healthy and 6 severely asthmatic horses in phase I, 10 severely asthmatic horses in phase II, and 10 healthy horses in phase III.
METHODS
Cohort (phases I and II) and cross-sectional (phase III) studies. Quantitative polymerase chain reaction primers targeting the sodA gene were optimized. N. semolina was quantified in oral and nasal washes and in bronchoalveolar lavage fluid (BALF; phase I, sampled twice), in nasal washes and BALF (phase II, sampled twice), and in nasal washes (phase III).
RESULTS
N. semolina was found in the nose of 5, 10, and 9 horses in phases I, II, and III, respectively (first sampling for phases I and II). Six BALF from 5 different horses were positive for N. semolina in phase II. In phase I, there was no significant difference in the nasal loads of healthy horses (median (range): 2.04 × 10 copies/mL (0-2.44 × 10 )) and asthmatic horses in exacerbation (3.75 × 10 (0-4.84 × 10 ); Wilcoxon's rank sum test, P = .57).
CONCLUSIONS AND CLINICAL IMPORTANCE
N. semolina is commonly found in the airways of horses. The potential pathogenicity of N. semolina remains to be elucidated, but the molecular technique we developed will facilitate future studies.
Topics: Animals; Asthma; Bronchoalveolar Lavage Fluid; Cross-Sectional Studies; Horse Diseases; Horses; Pasteurellaceae
PubMed: 33942932
DOI: 10.1111/jvim.16140 -
Journal of Paediatrics and Child Health Jul 2021
Topics: Epiglottitis; Haemophilus Infections; Haemophilus Vaccines; Haemophilus influenzae; Humans; Infant
PubMed: 32861222
DOI: 10.1111/jpc.15146