Neisseria gonorrhoeae- Antigenic/Virulence Factors, Resistance, Epidemiology

 Antigenic/Virulence Factors

 

•  Pili - Are hair like structures extending from the surface - made up of pilin proteins -                     -Pilin proteins are antigenically different in almost all strains- A single strain can produce several antigenically distinct pili. Piliated gonococci are usually virulent, whereas non-piliated strains are avirulent 

• Lipooligosaccharide – Outer membrane contains LOS-lipooligosaccharide (endotoxin) – responsible for toxicity 

• Outer membrane Proteins – many different proteins 

• Protein I (por) – Forms pore on surface. Each strain expresses one type of protein I. It helps in serotyping of gonococci. Two variants of protein I – IA & IB. Any one strain carries either IA or IB but not both. 24 serovars of type IA & 32 serovars of type IB. 
• Protein II (opa) – Opacity associated outer membrane protein (OPA). Help in attachment to host cell. Strains with OPA protein form opaque colonies.  
• Protein III – is associated with protein I in the formation of pores on the cell surface &  plays a role in the exchange of molecules across the outer membrane.

• IgA1 protease - The main host defenses against gonococci are antibodies (IgA and IgG), complement, and neutrophils. • IgA protease degrades and inactivates IgA which plays a major role in mucosal defense. 

•  Transferrin (Iron binding proteins) specifically bind and internalize iron from host‐derived proteins, including transferrin, lactoferrin

•  Plasmids-Gonococci contains several cryptic plasmids –  transmissible plasmids contain genes that code for beta lactamase which causes resistance to penicillin. 

Resistance

• Very delicate organism - Readily killed by drying, heat & antiseptic 
• Strict parasite & dies in 1 – 2 hours in exudate outside the body. 
• In culture, the coccus dies in 3 – 4 days but survives in slant culture at 35⁰C if kept under sterile paraffin oil. 
• Cultures – preserved for years if frozen quickly & stored at – ^- 70⁰C.

Epidemiology

• ·   Exclusively a human disease- no natural infection in animals. Experimental infection in chimpanzees (urethral inoculation)  and mice (intracerebral inoculation)
• ·         Humans-only source of infection
• ·         Asymptomatic carriage in women- major factor in spreading of infection
• ·         Fomites do not transmit the disease
• ·         The only non-venereal infection is Ophthalmia neonatorum/conjunctivitis of the newborn.- once very common, now controlled by the practice of administering 1% silver nitrate solution into the eyes of all newborns

 Mode of transmission

1.      Sexual transmission: Acquired during unprotected sex with infected partner.

2.      Neonates acquire Neisseria gonorrhoeae from mother during passage through the birth canal.  In newborn infants, Neisseria gonorrhoeae causes Ophthalmia neonatorum (purulent conjunctivitis).

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