Neisseria Genus and Meningitis Characteristics

Neisseria meningitidis is a Gram-positive bacterium.

The serotype of Neisseria meningitidis refers to the polysaccharide capsule.

Neisseria gonorrhoeae is a fastidious bacterium that can survive outside of neutrophils.

Neisseria meningitidis is aerobic and oxidase negative.

Pili are a virulence factor of Neisseria meningitidis that enhances resistance to phagocytosis and attachment to host cells.

College students are not a high-risk group for meningitis.

Neisseria gonorrhoeae is transmitted through casual contact.

The capsule of Neisseria meningitidis is antigenically homogeneous and cannot change to avoid host defenses.

Corynebacterium species are commonly found in the human microbiota of the skin, upper respiratory tract, GI tract, and Urogenital tract.

Corynebacterium diphtheriae is a Gram-negative, spore-forming bacillus.

The diphtheria toxin gene is encoded by the bacterium itself.

Corynebacterium diphtheriae causes disease in the late stage by inducing muscle weakness and edema.

The lethal dose of diphtheria toxin for humans is approximately 1 μg of toxin per kg of body weight.

Diphtheria toxin blocks DNA synthesis.

Neisseria Genus

Genus: Neisseria
Species: Gonorrhoeae and meningitidis

Characteristics

Gram negative cocci (Diplococci)
Non spore forming and non motile
Oxidase positive
Intracellular, usually found in polymorphonuclear cells
Aerobic

Neisseria meningitidis

Virulence factors:
- Capsule: antigenically heterogeneous and capable of changing to avoid host defenses
- Pili (Fimbriae): enhance attachment to host cells and resistance to phagocytosis
- Toxin: endotoxin lipid A part of lipopolysaccharide
- Enzyme: IgA protease

Meningitis

Inflammation of the membranes of the brain or spinal cord
High risk groups:
- Infancy
- Elderly
- Immunocompromised
- Head trauma
- Neural surgery
- College students
- Military recruits

Neisseria gonorrhoeae

Gram-negative
Oxidase positive
Aerobic and survives within neutrophils
Fastidious
Coccal (diplococcal arrangement)
Humans are the only natural hosts for gonococcus, transmitted through sexual intercourse

Corynebacterium

Genus of bacteria that are Gram-positive, aerobic, non-capsulated, and non-spore-forming bacilli.
Found in skin, upper respiratory tract, GI tract, and Urogenital tract of humans as part of human microbiota.
Also occur naturally in soil, water, plants, and food products.

Corynebacterium diphtheriae

Rod-shaped, Gram-positive, non-spore-forming, and non-motile bacterium.
Characterized by granules within rods stained with aniline dyes.
Causes the disease diphtheria.

Pathogenesis of Diphtheria

Early stage symptoms: sore throat, low fever, muscle weakness, edema, and pseudomembranous material in the upper respiratory tract.
Late stage symptoms: airway obstruction, breathing difficulty, and shock.

Virulence Factors: Diphtheria Toxin

Exotoxin secreted by Corynebacterium diphtheriae.
Toxin gene is encoded by a bacteriophage.
Extremely potent, with a lethal dose of approximately 0.1 μg of toxin per kg of body weight.
Causes death through necrosis of the heart and liver.
Blocks protein synthesis.

This quiz covers the characteristics of the Neisseria genus, specifically Neisseria gonorrhoeae and meningitidis, including their gram stain, motility, and virulence factors.