Neisseria Overview and Clinical Features

Neisseria Overview

• The genus Neisseria includes two major human pathogens: Neisseria meningitidis and Neisseria gonorrhoeae.
• N. meningitidis primarily causes meningitis and meningococcemia.
• N. gonorrhoeae causes gonorrhea, neonatal conjunctivitis (ophthalmia neonatorum), and pelvic inflammatory disease (PID).

Clinical Features of Neisseria

• Meningococcal Septicemia: Bacteria enter the bloodstream, multiply, and damage blood vessel walls.

Important Properties of Neisseria

• Gram-negative Cocci: Aerobic, non-motile, non-spore forming, and encapsulated.
• Morphology: Resemble paired kidney beans within neutrophils.
• Growth Requirements: Require enriched, complex media and CO2.
• Strict Parasites: Cannot survive long outside the host.
• Size: Ranges from 0.6-0.8 μm.
• Biochemical Properties: Oxidase-positive, non-acid-fast, produce catalase and oxidase.

Virulence Factors of Neisseria

• Polysaccharide Capsule (N. meningitidis): Enhances virulence by preventing phagocytosis (antiphagocytic action) and inducing protective antibodies.
  • Serogroups: Meningococci are divided into at least 13 serologic groups based on their capsular polysaccharides.
    • Five serotypes (A, B, C, Y, and W) cause most cases of meningitis and meningococcemia.
    • Serotype A is the leading cause of epidemic meningitis worldwide.
    • Serotype B accounts for most diseases in the United States.
  • Capsule Antigens: Used for vaccine development.
• Pilus Protein (N. gonorrhoeae): Responsible for multiple serotypes.
  • Antigenic Variation: Gonococcal pili undergo marked antigenic variation due to chromosomal rearrangement, leading to over 100 known serotypes.
  • Outer Membrane Proteins: Gonococci possess three outer membrane proteins (proteins I, II, and III).
    • Protein II plays a role in cell attachment and exhibits antigenic variation.
• Endotoxin: Found in the outer membrane, consists of lipo-oligosaccharide (LOS) (in contrast to lipopolysaccharide (LPS) found in enteric gram-negative rods).
  • Lipid A: Both LPS and LOS contain lipid A.
• Growth Inhibition: Inhibited by toxic trace metals and fatty acids present in certain culture media.
  • Culture Media: Cultured on "chocolate" agar, which contains blood heated to 80°C to inactivate inhibitors.
• Oxidase-positive: Possess the enzyme cytochrome c.

Neisseria

• This genus contains two important human pathogens: Neisseria meningitidis and Neisseria gonorrhoeae.
• N. meningitidis mainly causes meningitis and meningococcemia.
• In the United States, N. meningitidis is the leading cause of death from infection in children.
• N. gonorrhoeae causes gonorrhea, the second most common notifiable bacterial disease in the US.
• N. gonorrhoeae can also cause neonatal conjunctivitis (ophthalmia neonatorum) and pelvic inflammatory disease (PID).
• N. meningitidis is also known as the meningococcus, and N. gonorrhoeae is also known as the gonococcus.

Important Properties of Neisseria

• Neisseria species are Gram-negative cocci.
• They are aerobic (oxidative metabolism) and do not possess flagella or spores.
• They are capsulated, possess pili, require enriched complex media and CO2, and are oxidase-positive.
• Neisseria are non-acid-fast cocci that produce catalase and oxidase.
• They are strict parasites and do not survive long outside of the host.
• Their size ranges between 0.6–0.8 μm.

Important Properties and Virulence factors of Neisseria

• N. meningitidis has a prominent polysaccharide capsule that enhances virulence by its antiphagocytic action and induces protective antibodies.
• The polysaccharide capsule has antigenic properties.
• Meningococci are divided into at least 13 serologic groups based on the antigenicity of their capsular polysaccharides.
• Five serotypes cause most cases of meningitis and meningococcemia: A, B, C, Y, and W.
• Serotype A is the leading cause of epidemic meningitis worldwide.
• Serotype B accounts for most diseases in the United States.

N. gonorrhoeae

• N. gonorrhoeae does not have a polysaccharide capsule.
• It has multiple serotypes based on the antigenicity of its pilus protein.
• N. gonorrhoeae has three outer membrane proteins (proteins I, II, and III).
• Protein II plays a role in the attachment of the organism to cells and varies antigenically as well.

Antigenic Properties

• Neisseria are gram-negative bacteria and contain endotoxin in their outer membrane.
• The endotoxin of Neisseria consists of lipooligosaccharide (LOS), in contrast to the lipopolysaccharide (LPS) found in enteric gram-negative rods.
• Both LPS and LOS contain lipid A, but the oligosaccharide part of LOS contains fewer sugars, whereas the polysaccharide part of LPS contains a long repeating sugar side chain.

Growth and Culture of Neisseria

• The growth of N. meningitidis and N. gonorrhoeae is inhibited by toxic trace metals and fatty acids found in certain culture media (e.g., blood agar plates).
• Therefore, they are cultured on “chocolate” agar containing blood heated to 80°C, which inactivates the inhibitors.
• Neisseria are oxidase-positive (i.e., they possess the enzyme cytochrome c).

Neisseria Genus

• Contains two significant human pathogens: Neisseria meningitidis and Neisseria gonorrhoeae
• N. meningitidis primarily causes meningitis and meningococcemia, a bloodstream infection leading to blood vessel damage.
• N. meningitidis is a leading cause of infection-related deaths in children within the United States.
• N. gonorrhoeae is responsible for gonorrhea, the second most common bacterial infection reported in the US.
• N. gonorrhoeae also causes neonatal conjunctivitis (ophthalmia neonatorum) and pelvic inflammatory disease (PID).
• N. meningitidis is also known as the meningococcus, and N. gonorrhoeae is known as the gonococcus.

Clinical Features of Neisseria:

• Includes meningitis, meningococcemia, gonorrhea, neonatal conjunctivitis, and pelvic inflammatory disease

Important Properties of Neisseria

• Gram-negative cocci, appearing as paired kidney beans within neutrophils.
• Aerobic, using oxidative metabolism.
• Lack flagella and spores.
• Possess a capsule and pili.
• Require enriched complex media and CO2 for growth.
• Strict parasites, unable to survive long outside of a host.
• Size ranges from 0.6–0.8 μm.
• Oxidase-positive, catalase-positive, and non-acid-fast.

Important Properties and Virulence Factors of Neisseria

• N. meningitidis has a prominent polysaccharide capsule enhancing virulence through antiphagocytic action and inducing protective antibodies.
• Meningococci are classified into 13 serologic groups based on capsule polysaccharide antigenicity.
• Five serotypes (A, B, C, Y, and W) cause most meningitis and meningococcemia cases.
• Serotype A is the primary cause of epidemic meningitis globally, while Serotype B is most prevalent in the United States.
• Capsule antigens are vital components of vaccines.
• N. gonorrhoeae lacks a polysaccharide capsule.
• N. gonorrhoeae has multiple serotypes based on pilus protein antigenicity.
• Gonococcal pili exhibit significant antigenic variation due to chromosomal rearrangement, with over 100 known serotypes.
• Gonococci possess three outer membrane proteins (Proteins I, II, and III). Protein II facilitates cellular attachment and demonstrates antigenic variation.

Antigenic Properties

• Neisseria are gram-negative bacteria containing endotoxin in their outer membrane.
• Neisseria endotoxin consists of lipooligosaccharide (LOS) instead of lipopolysaccharide (LPS) seen in enteric gram-negative rods.
• Both LOS and LPS contain lipid A, but LOS contains few sugars compared to the long repeating sugar side chains in LPS.

Growth Characteristics

• N. meningitidis and N. gonorrhoeae growth is inhibited by toxic trace metals and fatty acids present in specific culture media, like blood agar plates.
• They are cultivated on "chocolate" agar, containing blood heated to 80°C, which inactivates growth inhibitors.
• Neisseriae are oxidase-positive, meaning they possess the enzyme cytochrome c.

Neisseria Genus

• Contains two important human pathogens: Neisseria meningitidis and Neisseria gonorrhoeae
• N. meningitidis primarily causes meningitis and meningococcemia.
  • Meningococcemia: bacteria enter bloodstream, multiply, damage blood vessel walls.
  • In the United States, it is the leading cause of death from infection in children.
• N. gonorrhoeae causes:
  • Gonorrhea, the second most common notifiable bacterial disease in the United States.
  • Neonatal conjunctivitis (ophthalmia neonatorum)
  • Pelvic inflammatory disease (PID)

Clinical Features of Neisseria

• N. meningitidis is also known as the meningococcus (plural, meningococci).
• N. gonorrhoeae is also known as the gonococcus (plural, gonococci).

Important Properties of Neisseria

• Gram-negative cocci
• Aerobic (oxidative metabolism)
• Lack flagella and spores
• Capsulated with pili
• Require enriched complex media and CO2
• Diplococus with a flattened or concave shape, resembling paired kidney beans within neutrophils.
• Strict parasites, unable to survive long outside of the host.
• Size ranges between 0.6–0.8 μm
• Oxidase-positive, non-acid-fast cocci
• Produce catalase and oxidase

Important Properties and Virulence Factors of Neisseria

N. meningitidis (meningococcus)

• Has a prominent polysaccharide capsule
  • Enhances virulence by antiphagocytic action and induces protective antibodies.
  • Meningococci are divided into at least 13 serologic groups based on their capsular polysaccharides.
  • Five serotypes cause most cases of meningitis and meningococcemia: A, B, C, Y, and W.
  • Serotype A is the leading cause of epidemic meningitis worldwide.
  • Serotype B accounts for most diseases in the United States.
  • Capsule antigens are used in the formulation and manufacture of vaccines.

N. gonorrhoeae (gonococcus)

• Lacks a polysaccharide capsule
• Has multiple serotypes based on the antigenicity of its pilus protein.
  • There is marked antigenic variation in the gonococcal pili as a result of chromosomal rearrangement; more than 100 serotypes are known.
• Gonococci have three outer membrane proteins (proteins I, II, and III).
  • Protein II is involved in attachment to cells and is also antigenically variable.

Antigenic Properties

• Neisseria are gram-negative bacteria and contain endotoxin in their outer membrane.
  • Endotoxin consists of lipooligosaccharide (LOS), unlike the lipopolysaccharide (LPS) found in enteric gram-negative rods.
  • Both LOS and LPS contain lipid A, but LOS has few sugars while LPS has a long repeating sugar side chain.

Growth of Neisseria

• The growth of both N. meningitidis and N. gonorrhoeae is inhibited by toxic trace metals and fatty acids found in certain culture media (e.g., blood agar plates).
  • Cultured on "chocolate" agar containing blood heated to 80°C, which inactivates the inhibitors.
• Neisseriae are oxidase-positive (due to cytochrome c enzyme).