Neisseria 1

• What type of bacteria is Neisseria?

  Gram negative bacteria
• What is the shape of Neisseria bacteria?

  Gram negative diplococci, resembling kidney beans
• What is a key biochemical characteristic of Neisseria?

  Oxidase positive
• What are the two important human pathogens of Neisseria?

  • Neisseria meningitidis (meningococci)
  • Neisseria gonorrhoeae (gonococci)
• What is a significant feature of Neisseria meningitidis?

  It is encapsulated and ferments glucose and maltose
• How do Neisseria gonorrhoeae and Neisseria meningitidis differ in terms of penicillin susceptibility?

  Most strains of Neisseria meningitidis are susceptible to penicillin, while most strains of Neisseria gonorrhoeae are resistant (PPNG)
• What are the virulence factors of Neisseria meningitidis?

  • Capsule: Polysaccharide, antiphagocytic
  • Lipooligosaccharide (LOS): Causes cytokine activation
  • IgA protease: Cleaves mucosal IgA
  • Pili: Adherence to mucosal wall
  • Outer membrane proteins (OMP): Attachment to epithelial cells
• What are the main infections caused by Neisseria meningitidis?

  Meningitis and meningococcal septicemia (meningococcemia)
• What percentage of the population are asymptomatic carriers of Neisseria meningitidis?

  1. 30% of the population
• When do epidemics of Neisseria meningitidis typically occur?

  Epidemics occur in late winter and early spring
• How is Neisseria meningitidis transmitted?

  By aerosol droplets through close contact
• What are common settings for Neisseria meningitidis epidemics?

  • Military camps
  • Dormitories
  • Schools and colleges
  • Pilgrims (Haj)
• What is the pathogenesis of Neisseria meningitidis?

  1. Attachment to non-ciliated columnar epithelial cells of the nasopharynx
  2. Invasion
  3. Dissemination and multiplication through the bloodstream (septicemia)
  4. Possible CNS invasion through hematogenous spread
• What are the pathological effects of meningitis caused by Neisseria meningitidis?

  • Marked attribution of polymorphs
  • Increased blood-brain barrier (BBB) permeability
• What are the pathological effects of septicemia caused by Neisseria meningitidis?

  • Septic shock
  • Endothelial damage and vasculitis
  • Thrombocytopenia
  • Disseminated intravascular coagulation (DIC)
  • Bilateral adrenal apoplexy and adrenal insufficiency (Waterhouse–Friderichsen syndrome)
• What are the host defenses against Neisseria meningitidis infections?

  • Upper respiratory mucosal barriers
  • Circulating protective IgG and IgM
  • Complement
• What are the clinical manifestations of meningitis caused by Neisseria meningitidis?

  • Symptoms: Fever, headache, neck stiffness, photophobia
  • Diverse symptoms in infants: Poor feeding, lethargy, irritability
• What are the signs of meningitis caused by Neisseria meningitidis?

  • Nuchal rigidity
  • Kernig’s sign
  • Brudzinski’s sign
  • Bulging anterior fontanelles in infants
  • Skin rash
• What are the complications of meningitis caused by Neisseria meningitidis?

  • Increased intracranial pressure: Headache, vomiting, blurred/double vision, papilledema
  • Motor/sensory deficits: e.g., hearing loss
  • Cerebral herniation
  • Hydrocephalus
  • Syndrome of inappropriate ADH secretion (SIADH)
• What are the clinical manifestations of meningococcemia caused by Neisseria meningitidis?

  • Nonspecific symptoms: Cough, headache, sore throat
  • Fever, chills, arthralgia, myalgia
• What are the signs of fulminant meningococcemia?

  • Skin petechial and purpuric lesions
  • Arthritis
  • Congestive heart failure
• What specimens are used for diagnosing Neisseria meningitidis infections?

  • Blood (for septicemia)
  • CSF (for meningitis via lumbar puncture)
  • Pharyngeal swabs (for carrier screening)
  • Skin samples from subcutaneous hemorrhages
• What are the characteristics of CSF in meningitis caused by Neisseria meningitidis?

  • Macroscopy: Turbid, xanthochromic
  • High protein levels
  • Low glucose levels
  • Predominance of neutrophils
• What is the staining characteristic of Neisseria meningitidis in diagnosis?

  Gram negative intracellular diplococci
• What culture medium is used for Neisseria meningitidis?

  Chocolate blood agar, which produces small smooth transparent colonies
• What biochemical reactions are characteristic of Neisseria meningitidis?

  Oxidase positive and utilizes glucose and maltose
• What tests are used for sero-grouping of Neisseria meningitidis?

  • Latex agglutination test
  • Molecular typing
  • Antimicrobial susceptibility tests
• What is the empirical treatment for Neisseria meningitidis infections?

  • 3rd generation cephalosporin (ceftriaxone)
  • Penicillin G
  • Prophylaxis: Rifampin or ciprofloxacin