Neisseria spp. Overview and Key Characteristics

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Questions and Answers

Which Neisseria species is primarily responsible for causing meningitis?

Neisseria gonorrhoeae

Neisseria sicca

Neisseria lactamica

Neisseria meningitidis (correct)

What type of culture medium is typically used for isolating Neisseria species?

Sabouraud agar

Chocolate agar (correct)

Nutrient agar

Mannitol salt agar

What is a distinguishing characteristic of Neisseria meningitidis compared to Neisseria gonorrhoeae?

Production of endotoxin

Ability to cause pelvic inflammatory disease

Presence of a polysaccharide capsule (correct)

More than 100 serotypes

Which statement about Neisseria gonorrhoeae is incorrect?

It is gram-positive cocci. Signup and view all the answers

How does Neisseriae react in the oxidase test?

It turns purple or black. Signup and view all the answers

What component is found in the outer membrane of Neisseriae that contributes to its pathogenicity?

Lipooligosaccharide (LOS) Signup and view all the answers

Which serotype of Neisseria meningitidis is known to be the leading cause of epidemic meningitis worldwide?

Serotype A Signup and view all the answers

What is the role of Protein II in Neisseria gonorrhoeae?

It aids in the organism's attachment to host cells. Signup and view all the answers

What is the main mode of transmission for Neisseria meningitidis?

Airborne droplets Signup and view all the answers

Which of the following is NOT a virulence factor of Neisseria meningitidis?

Pili Signup and view all the answers

What is the preferred treatment for meningococcal infections?

Penicillin G Signup and view all the answers

What factor contributes to the asymptomatic nature of many Neisseria gonorrhoeae infections in women?

Anatomical differences in the genital tract Signup and view all the answers

What distinguishes a chronic carrier of Neisseria meningitidis?

Ability to transmit the bacteria to others Signup and view all the answers

Which of the following is a common laboratory procedure for diagnosing meningococcal infections?

Smear and culture of blood and spinal fluid Signup and view all the answers

How do pili function as a virulence factor in Neisseria gonorrhoeae?

Facilitate attachment to mucosal surfaces Signup and view all the answers

What is the role of chemoprophylaxis in the prevention of meningococcal disease?

To prevent infection in exposed individuals Signup and view all the answers

Study Notes

Neisseria spp. (Gram-negative cocci)

Neisseria contains two important human pathogens: N. meningitidis and N. gonorrhoeae.
N. meningitidis causes meningitis and meningococcemia, characterized by purpuric lesions (Figure 1).
N. gonorrhoeae causes gonorrhea, neonatal conjunctivitis (ophthalmia neonatorum) (Figure 2), and pelvic inflammatory disease (PID).
N. meningitidis is also known as the meningococcus.
N. gonorrhoeae is also known as the gonococcus.

Important Properties of Neisseria

Gram-negative cocci, resembling paired kidney beans.
Growth inhibited by certain trace metals and fatty acids in culture media.
Cultured on chocolate agar (blood agar heated to 80°C).
Oxidase-positive (possessing cytochrome c enzyme). Colonies exposed to phenylenediamine turn purple or black.

N. meningitidis

Has a polysaccharide capsule (Table 3).
Divided into serogroups (at least 13) based on capsular polysaccharide antigenicity.
Five serotypes (A, B, C, Y, and W-135) cause most cases of meningitis and meningococcemia.
Serotype A is the leading cause of epidemic meningitis.

N. gonorrhoeae

Lacks a polysaccharide capsule.
Multiple serotypes based on pilus protein antigenicity (over 100 known).
Has three outer membrane proteins (I, II, and III) that play a role in cell attachment.
Protein II displays antigenic variation.

Neisseria Endotoxin

Neisseria contain endotoxin (lipooligosaccharide, LOS) in their outer membrane.

Pathogenesis and Epidemiology (N. meningitidis)

Humans are the only natural hosts for N. meningitidis.
Transmitted via airborne droplets.
Colonizes the nasopharynx.
Carriers can be asymptomatic.
Can disseminate into the bloodstream, meninges, joints, etc.
Carriage rate can be high in close quarters (up to 35%).

N. meningitidis Virulence Factors

Polysaccharide capsule (resists phagocytosis by PMNs).
Endotoxin (causes fever, shock).
Immunoglobulin A (IgA) protease (affects bacterial attachment).

Laboratory Diagnosis

Smear and culture of blood and spinal fluid samples.
Immunofluorescence can be helpful.
Nucleic acid amplification tests are used for screening.

Treatment

Penicillin G is the treatment of choice for meningococcal infections.
Ceftriaxone can be used as an alternative, especially if allergies to penicillin exist.

Prevention

Chemoprophylaxis (rifampin, ciprofloxacin).
Immunization (capsular polysaccharide of groups A, C, Y, and W-135).

Pathogenesis and Epidemiology (N. gonorrhoeae)

Primarily a sexually transmitted infection.
Colonizes mucous membranes (genital, anal, pharyngeal).
Pili (important virulence factors): mediate attachment to host cells.
Lipooligosaccharide (LOS) and outer membrane proteins also contribute to virulence.
IgA protease: degrades IgA, hindering immune response.

Laboratory Diagnosis (N. gonorrhoeae)

Gram staining and culture of discharge.
Nucleic acid amplification tests, are increasingly utilized for screening.

Treatment (N. gonorrhoeae)

Ceftriaxone is the treatment of choice.
Alternatives (azithromycin, ciprofloxacin) are available for penicillin or cephalosporin allergies.

Prevention (N. gonorrhoeae)

Treatment of symptomatic patients.
Detection of asymptomatic carriers (a major problem).
Use of erythromycin ointment for prevention of gonococcal conjunctivitis in newborns.

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Description

This quiz covers the essential properties and important human pathogens of the Neisseria genus, including N. meningitidis and N. gonorrhoeae. Learn about their characteristics, growth requirements, and clinical significance. Ideal for students studying microbiology or infectious diseases.