17: Fusobacterium, Neisseria, Veillonella, & Aggregatibacter

Question 1

Neisseria gonorrhoeae
-gram +/-
-shape
-Identification of agar

Answer 1

-gram -
-diplococci
-all (+) catalase, glucose, oxidase

transmitted via sexual transmission and birth canal

Question 2

Neisseria gonorrhoeae
virulence factors

Answer 2

-Pilli (fimbriae)
-Immunglobulin A (IgA) proteases
-B-lactamase
-tracheal cytotoxin damages the fallopian tube, leading to scarring and sterility

Question 3

Neisseria gonorrhoeae pathogenesis

Answer 3

Once it infects mucosal surfaces, N. gonorrhoeae can cause:
-Urethritis
-Cervicitis
-Ophthalmia neonatorum
-tracheal cytotoxin this cytotoxin damages the fallopian tube, leading to scarring and sterility
Although the name suggests an effect on the trachea, TCT also affects other mucosal surfaces, including the fallopian tubes in women.

Question 4

Neisseria meningitidis
-gram +/-
-shape
-surface antigens
-niche
-Lab identification

Answer 4

-gram -
-diplococci
-surface antigens= A,B,C,Y and W135 types
-throat and nasopharynx
-all (+) Oxidase, catalase, glucose, maltose

Question 5

Neisseria meningitidis virulence factors

Answer 5

-pilli
-capsule
-porins porA and porB
-iron sequestration
-LOS endotoxin
-immunoglobulin A1 protease
-intracellular growth/surviving phagocytosis

Question 6

What triggers the systemic inflammatory response in meningococcal septicemia?

Answer 6

The release of bacterial endotoxins, particularly lipooligosaccharides (LOS), leads to a cytokine storm and widespread inflammation.

disseminated intravascular coagulation, necrosis and infarction of organs, hemorrhage into internal organs, hypocalcemia and post-recovery bone abnormalities

potential dental defects
-discoloration
-defective enamel
-premature loss of teeth
-malocclusion/crowding
-ectopic eruption
-fail to erupt

Question 7

Fusobacterium nucleatum
-where is it found
-gram +/-
-shape
-w/ or w/o O2

Answer 7

found in the healthy gingival crevice and periodontal pockets
gram -
cigar-shaped bacilli
-anaerobes

Question 8

Adhesion A (FadA)

Answer 8

FadA is a significant virulence factor in Fusobacterium nucleatum that facilitates adhesion to host cells.

Question 9

Necrotizing ulcerative gingivitis caused by

Answer 9

Necrotizing ulcerative gingivitis (NUG) is a severe form of gum disease caused by
-F.nucleatum
-Prevotella intermediate
-oral spirochetes

Question 10

Necrotizing ulcerative gingivitis clinical manifestation

Answer 10

It is a type of necrotizing periodontal disease caused by F.nucleatum

characterized by
-painful, inflamed (swollen and red), and ulcerated gingival tissues **Punched out” crater-like depressions at the tip of the inter-dental papilla
-grayish pseudomembrane covering depressions
-metallic taste, thick saliva

Question 11

Veillonella
-gram +/-
-shape
-w/or w/o O2
-late/early colonizer
-production
-found in

Answer 11

Gram -
Cocci
Anaerobic
Early colonizer
Lactic acid - acetic acid and propionic
-found in dental plaque

These bacteria are known for their ability to metabolize lactate, which is produced by other bacteria, especially during carbohydrate fermentation. By consuming lactate, Veillonella can reduce the acidity in the oral environment, potentially lowering the risk of dental caries (tooth decay).

Question 12

Aggregatibacter actinomycetemcomitans
-gram +/-
-w/ or w/o O2
-early or late colonizer
-found in
-plays a significant role in

Answer 12

Gram -
Anaerobic
Late
Found in human subgingival sites
plays a significant role in periodontal diseases, particularly aggressive periodontitis.

It is part of the HACEK group of bacteria, which are often associated with endocarditis but are most notable for their involvement in oral and systemic infections

Question 13

Virulence factors for Aggregatibacter actinomycetemcomitans

Answer 13

Virulence factors: contribute to its pathogenicity
leukotoxins
Cytolethal distending toxin (CDT)
Epitheliotoxin bone resorption
lipopolysaccharides (LPS)
Fimbriae (adhesion)

CDT is unique because it causes host cells to distend (swell) and eventually undergo cell cycle arrest, followed by apoptosis (programmed cell death).

Epitheliotoxin-induced bone resorption refers to a process where bacterial toxins target epithelial cells, leading to inflammation and the subsequent breakdown of bone tissue. This process is particularly relevant in periodontal diseases, where toxins produced by pathogenic bacteria in the oral cavity not only damage the soft tissues (gums) but also contribute to the destruction of the underlying bone

Question 14

Which bacteria is known to cause localized aggressive periodontitis in adolescents and destructive periodontal disease in adults?

Answer 14

Aggregatibacter actinomycetemcomitans

Question 15

Which serotype of Aggregatibacter actinomycetemcomitans is more common in aggressive periodontitis?

Answer 15

Serotype B

More aggressive than serotype A-E

Question 16

Which bacteria is an opportunistic pathogen having an inflammatory mechanism leading to bone loss in periodontitis

Answer 16

Aggregatibacter actinomycetemcomitans

Question 17

Which bacteria contains Leukotoxins as a virulence factor?

Answer 17

Aggregatibacter actinomycetemcomitans

Leukotoxin: A toxin that forms large pores that can destroy human immune cells particularly neutrophils. This impairs the host’s immune response and helps the bacteria evade immune defense.

Question 18

What type of secretion system is produced by leukotoxin and what is its role?

Answer 18

The type 1 secretion system (T1SS) is the mechanism by which leukotoxin, produced by Aggregatibacter actinomycetemcomitans, is transported out of the bacterial cell into the surrounding environment or directly into host cells (to the outer membrane of the bacteria)

Question 19

Which bacteria contains Cytolethal distending toxin as a virulence factor?

Answer 19

Aggregatibacter Actinomycetemcomitans

CDT is unique because it causes host cells to distend (swell) and eventually undergo cell cycle arrest of T cells,macrophages, Hepatitis-2 cells and epithelial cells, followed by apoptosis (programmed cell death) of T cells, non-proliferating and proliferating macrophages

Question 20

Which bacteria contains Cytolethal distending toxin as a virulence factor?

Answer 20

Aggregatibacter Actinomycetemcomitans

CDT is unique because it causes host cells to distend (swell) and eventually undergo cell cycle arrest of T cells,macrophages, Hepatitis-2 cells and epithelial cells, followed by apoptosis (programmed cell death) of T cells, non-proliferating and proliferating macrophages

Question 21

How many subunits does Cytolethal distending toxin have? And what are their roles?

Answer 21

CDT is a tripartite toxin composed of three subunits:

CdtA: The binding subunit, which helps attach the toxin to the host cell surface.
CdtB: The enzymatic subunit, which acts as a DNase (deoxyribonuclease). It is the active component that enters the host cell and damages DNA.
CdtC: Another binding subunit that helps facilitate the entry of the toxin into host cells.

Question 22

What type of cells are arrested by Cytolethal distending toxin?? And which are the cells that after being arrested will the Cytolethal distending toxin induce apoptosis?

Answer 22

Arrest the cell cycle of T cell, macrophages, Hep-2 cells, and many epithelial cells

Induce apoptosis in T cells, and macrophages (proliferating and non-proliferating)

Question 23

Chaperonin 60 is found in what bacteria and what is its role?

Answer 23

Aggregatibacter actinomycetemcomitans
Is considered a potent bone-degrading molecule because it acts as an osteoclasts ‘growth factor”

Question 24

Biofilm formation is mediated by what? and is associated with what bacteria?

Answer 24

Poly-N-acetylglucosamine is a surface polysaccharide that mediates biofilm formation, intracellular adhesion, and detergent resistance.

Aggregatibacter actinomycetemcomitans: associated with periodontal disease

Question 25

What mediates aggregation and colonization to the gingival crevice epithelium by Aggregatibacter actinomycetemcomitans?

Answer 25

Surface antigens like vesicles
These vesicles may contain Poly-N-acetylglucosamine

Question 26

What types of collagen does poly-N-acetylglucosamine bind to

Answer 26

binds to collagen types I, II, III, and V, but not type IV.

Question 27

What extracellular matrix protein does poly-N-acetylglucosamine bind to?

Answer 27

binds to fibronectin but not to fibrinogen.

Question 28

OMP34

Answer 28

outer membrane protein 34
and an immunomodulatory virulence factor of Aggregatibacter actinomycetemcomitans.

helping the bacterium evade the host immune response.

Question 29

Which virulence factor of A. Actinomycetemcomitans acts as an immunomodulatory?

Answer 29

OMP34

Question 30

Which virulence factor of A. Actinomycetemcomitans acts as an immunomodulatory?

Answer 30

OMP34

helping the bacterium evade the host immune response.

Question 31

What type of protein is Omp34 similar to in Escherichia coli?

Answer 31

Omp34 is similar to OmpA, which also serves as an Fc binding protein

Question 32

What is the significance of Omp34’s ability to bind the Fc region of antibodies?

Answer 32

This binding hinders antibody-mediated immune responses, preventing effective opsonization and clearance of the bacteria.

Question 33

What is the significance of Omp34’s ability to bind the Fc region of antibodies?

Answer 33

This binding hinders antibody-mediated immune responses, preventing effective opsonization and clearance of the bacteria.

Question 34

How does Omp34 interact with the IL-10 receptor?

Answer 34

Omp34 binds to the IL-10 receptor, interfering with IL-10 signaling and promoting a more favorable environment for bacterial survival. Interfering with chemotaxis = preventing immune cells from reaching the site of infection and facilitating bacterial colonization.

Question 35

Extra oral infections caused by actinomycetemcomitans

Answer 35

Brain meninges
Septicemia
UTI
Osteomyelitis
Endocarditis and abscesses