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Neisseria gonorrhoeae : Basics

Neelam Maurya

Neisseria gonorrhoeae : Basics

Introduction 

  • N. gonorrhoea infections have a high prevalence and low mortality 
  • Is “obligate pathogen” and is never part of the normal human flora under any circumstances.
  • Gonococci is exclusive to humans
  • The only source of infection is a human carrier or less often a patient. 
  • In women gonococcus usually cause asymptomatic infection
  • In men the infection is usually symptomatic.

Morphology

  • Gram negative organism.
  • Possess pili on their surface:
  • facilitate adhesion of cocci to mucosal surface
  • promote virulence by inhibiting phagocytosis.
Cultural Characterstics
  • Need 5-10% CO2
  • Selective medium forgrowth is Thayer – Martin medium.
  • Four types of colonies have been recognised.
  • Type 1 and 2 are virulent
  • 3, 4 are non virulent cocci.

Biochemical reactions:

  • Ferment
  • glucose
  • (not maltose Neisseria meningitides ferment maltose)

Rapid carbohydrate utilisation test (RCUT):

  • This is a rapid, sensitive and specific test for detection of gonococci. 

Pathogenic factors
Outer-membrane protein: 

Pilli

Adherence    and Virulence 

Opacity associated protein (ProteinII)

Adhesion

Porin (Protein I, III) –

Surface  protein

H.8 Lipoprotein –

Target for antibody based diagnostic testing

Transferrin and lactoferrin bindingprotein.

Binding

IgAl protease

Also produced by meningococci

 Lipooligosaccharide 

  • Endotoxin
  • Resemble human glycosphingolipid
  • Contributes to the local cytotoxic effects.

Host factors

  • Defeciency of terminal complement components.
Exam Question
 

Introduction 

  • Obligate pathogen
  • Gonococci is exclusive to humans

Morphology

  • Gram negative organism.
  • Possess pili on their surface
Cultural Characterstics
  • Thayer – Martin medium.
  • Four types of colonies have been recognised.
  • Type 1 and 2 are virulent
  • 3, 4 are non virulent cocci.

Biochemical reactions:

  • Ferment
  • glucose
  • (not maltose Neisseria meningitides ferment maltose)

Rapid carbohydrate utilisation test (RCUT):

  • This is a rapid, sensitive and specific test for detection of gonococci. 

Pathogenic factors
Outer-membrane protein: 

Pilli

Adherence    and Virulence 

Opacity associated protein (Protein II)

Adhesion

Porin (Protein I, III) –

Surface  protein

H.8 Lipoprotein –

Target for antibody based diagnostic testing

Transferrin and lactoferrin binding protein.

Binding

IgAl protease

Also produced by meningococci

 Lipooligosaccharide 

  • Endotoxin
  • Resemble human glycosphingolipid
  • Contributes to the local cytotoxic effects.

Host factors

  • Defeciency of terminal complement components.
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