Neisseria

• Gonococci and meningococci


  Closely related, with 70% DNA homology
• Neisseria


  • Aerobic
  • Gram-negative
  • Nonmotile
  • Oxidase positive
  • Diplococcs, Kidney bean shape
• Culture


  1. Blood agar

  2. Chocolate agar

  3. Selective agar media (eg, modified Thayer-Martin agar +vancomycin + colistin+ nystatin + trimethoprim)
• Neisseria meningitidis


  Causes meningitis and life-threatening sepsis (meningococcemia)
• Virulence factors of Neisseria meningitidis

  • Capsule (polysaccharide, antiphagocytic)
  • Endotoxin (LPS) (causes blood vessel destruction, sepsis, petechial rash, adrenal gland damage)
  • IgA1 protease (cleaves IgA)
  • Pili
  • Por A and Por B
• Neisseria meningitidis is the normal flora of the nasopharynx, 5% of the population are carriers
• Infants are at high risk from age 6 months to 2 years
• Meningococcal Disease


  • Spreads via respiratory secretions
  • Invade the bloodstream (bacteremia) from the nasopharynx, resulting in meningitis and/or deadly sepsis (meningococcemia)
• Invasive meningococcal clue


  Petechial rash
• Meningococcemia (sepsis)


  1. Spiking fevers

  2. Chills

  3. Arthralgia (joint pains)

  4. Muscle pains

  5. Petechial rash
• Fulminant meningococcemia (Waterhouse Friderichsen syndrome)


  • Septic shock
  • Bilateral hemorrhage into the adrenal glands
  • Abrupt onset of hypotension and tachycardia
  • Rapidly enlarging petechial skin lesions
  • Disseminated intravascular coagulation (DIC) and coma may develop
  • Death can occur rapidly (6-8 hours)
• Meningitis in infants


  1. Fever

  2. Vomiting

  3. Irritability

  4. Stiff neck

  5. Petechial skin rash
• Causes of meningitis in infants

  • Within first 3 months of age: Listeria monocytogenes, Escherichia coli and Group B Streptococcus
  • Later: Neisseria meningitidis and Haemophilus infiuenzae
• Neisseria gonorrhoeae


  • Antigenically heterogeneous
  • Pili (hypervariable amino acid sequences, adhere to host, prevent phagocytosis)
  • Outer membrane protein porins (PorA and PorB) (promote invasion into epithelial cells)
  • Opa proteins (promote adherence and invasion into epithelial cells)
  • IgA1 protease (splits and inactivates IgA)
• Gonococcal Disease in Men

  • Causes gonorrhea, a sexually transmitted disease (STD)
  • Urethritis, with yellow creamy pus and painful urination
  • Some men will remain asymptomatic
  • Complications: epididymitis, prostatitis, and urethral strictures
  • Men having sex with men (referred to as MSM) results in rectal gonococcal infection
• Gonococcal Disease in Women

  • Causes gonococcal urethritis, women is more likely to be asymptomatic with minimal urethral discharge
  • Infects columnar epithelium of the cervix: purulent exudate
  • Can progress to pelvic inflammatory disease (PID) (Endometritis, salpingitis, oophoritis)

  
• Complications of PID


  • Sterility
  • Ectopic pregnancy (both caused by scarring of the fallopian tubes)
  • Abscesses (in the fallopian tubes, ovaries, or peritoneum)
  • Peritonitis
  • Peri-hepatitis (Fitz-Hugh-Curtis syndrome)

  
• Gonococcal Disease in Both Men and Women

  • Gonococcal bacteremia (disseminated infection: pericarditis, endocarditis, and meningitis)
  • Septic arthritis (Gonococcal arthritis is the most common kind of septic arthritis in young, sexually active individuals)
• Gonococcal Disease in Infants


  • During delivery cause ophthalmia neonatorum (occurs on the first or second day of life and can damage the cornea, causing blindness)
  • Gonococcal conjunctivitis can occur in adults
• Antigenic diversity of Neisseria

  • Chromosomal mutation
  • Plasmid transfer
• Antigenic diversity makes immunity difficult, resistance to antibiotics, and serology tests unreliable
• Diagnosis of Neisseria


  1. Specimen: Pus from the urethra, cervix, rectum, conjunctiva,…etc or blood, cerebrospinal fluid, or petechial scrapings

  2. Doughnut-shaped diplococci can be seen within the white blood cells

  3. Gram stain and culture on Thayer-Martin VCN medium

  
• Doughnut-shaped diplococci