Meningococcus | Medical Science Optional Notes for UPSC PDF Download

Diseases Caused by Meningococcus

• Neisseria meningitidis
• A gram-negative, aerobic diplococcus
• Non-sporing, non-motile, encapsulated
• Exhibits a kidney-shaped morphology with concave or semicircular ends that are flat and opposing.
• Upon acquiring the organism, susceptible individuals manifest disease symptoms within 1-10 days.

Spectrum of diseases caused by Meningococcus

Fever with Rash

A non-blanching rash (petechial or purpuric), which does not fade under pressure, is indicative of meningococcal septicemia, often assessed using the glass test. It's worth noting that most patients with a petechial or purpuric rash typically have a viral infection.

Common Causes of Petechial or Purpuric Rashes:

• Enteroviruses
• Influenza and various respiratory viruses
• Measles virus
• Epstein-Barr virus
• Cytomegalovirus
• Parvovirus
• Protein C or S deficiency (including post-varicella protein S deficiency)
• Platelet disorders (e.g., idiopathic thrombocytopenic purpura, drug effects, bone marrow infiltration)
• Conditions like Henoch-Schonlein purpura, connective tissue disorders, trauma (including non-accidental injuries in children)
• Bacterial sepsis from pneumococcal, streptococcal, staphylococcal, or gram-negative bacteria.

Meningitis (30-50%)

• Fever accompanied by a rash (petechial or purpuric)
• Vomiting
• Irritability
• Headache
• Stiffness in the neck
• Sensitivity to light (Photophobia)
• Reduced level of consciousness
• Seizures
• Focal neurological deficits

Infants and young children-fever, irritability and bulging fontanelle.

Signs of Meningism

Kernig Sign

• The Kernig sign can be evaluated through two approaches.
• In the first method, the extended leg is raised passively at the hip joint. Pain or discomfort triggers a reflex flexion of the knee.
• Alternatively, the Kernig sign can be examined by flexing the hip and knee to a 90° angle. Extending the leg from this position induces stretching of the nerve roots or meninges, potentially causing pain and muscle guarding against extension.

Brudzinski Sign

• When the neck is passively flexed, it triggers an automatic flexion of the hips as a reflex, offering relief from painful tension on the meninges.

Meningococcal Septicemia (20%)

• Exhibits a high mortality rate (25-40%)
• Rapid progression leading to death within hours
• Characterized by Purpura fulminans (large purpuric lesions)
• Shock
• Multiorgan failure

Pathogenesis

• The colonization of the nasopharynx involves a series of interactions between meningococcal adhesins (e.g., Opa proteins and pili) and their ligands on the epithelial mucosa.
• N. meningitidis produces an IgA1 protease, likely reducing disruption of colonization by mucosal IgA.
• The meningococcal capsule serves as a crucial virulence factor; acapsular strains rarely cause invasive disease. The capsule offers resistance to phagocytosis and may play a role in preventing desiccation during transmission between hosts.
• The majority of cases are attributed to only five serogroups (A, B, C, Y, and W135).
• The severity of meningococcal disease is linked to both the levels of endotoxin in the blood and the intensity of the inflammatory response.

Lab Diagnosis of Meningococcus

CSF Analysis in Meningitis

Repeats

• Explore the pathogenicity and laboratory diagnosis of meningococcal meningitis (2016).
• Provide a concise overview of the pathogenesis and laboratory diagnosis of meningococcal meningitis. Describe the complications and management of acute meningococcal meningitis (2011).