Microbial Diseases of the Nervous System - In-Depth Notes

Routes of Entry:
- Fractures: Skull or backbone fractures can allow microbes to enter.
- Medical Procedures: Surgical procedures may introduce microbes.
- Peripheral Nerves: Infection can spread along peripheral nerves.
- Blood or Lymph: Microbes can travel through blood or lymphatic systems to reach the CNS.

Components:
- Central Nervous System (CNS): Brain and spinal cord.
- Peripheral Nervous System (PNS): Nerves outside the CNS.

Bacterial Meningitis:
- Inflammation of Meninges: This condition can be life-threatening.
- Symptoms: Fever, headache, stiff neck, nausea, vomiting, and may progress to convulsions and coma.
- Diagnosis: Can be confirmed via Gram stain or latex agglutination of cerebrospinal fluid (CSF).
- Treatment: Typically treated with cephalosporins.
- Leading Causes of Bacterial Meningitis:
- Haemophilus influenzae
- Streptococcus agalactiae
- Neisseria meningitidis
- Listeria monocytogenes
- Streptococcus pneumoniae

Causative Agent: Neisseria meningitidis.
Transmission: Via salivary droplets; can be rapidly fatal (shock and death within 24 hours).
Symptoms: Massive inflammatory response, cessation of nutrient flow to the brain.

Characteristics: Gram-positive diplococci; common in children (1 month to 4 years).
Mortality Rate: About 30% in children, rising to 80% in the elderly.
Prevention: Through vaccination.

Causative Agent: Listeria monocytogenes, a foodborne disease.
Transmission: Associated with foods like soft cheeses and unpasteurized milk.
Characteristics: Can infect CNS by crossing intestinal linings; capable of growth in refrigerated conditions.

Causative Agent: Clostridium tetani; Gram-positive, endospore-forming, obligate anaerobe.
Mechanism: Releases tetanospasmin, blocking muscle relaxation pathways.
Prevention: Vaccination with tetanus toxoid; treatment includes tetanus immune globulin.

Causative Agent: Clostridium botulinum; leads to flaccid paralysis from toxin ingestion.
Prevention Measures: Proper canning techniques and addition of nitrites in processed foods.
Symptoms: Include blurred/double vision, muscle weakness, and paralysis if untreated.

Causative Agent: Mycobacterium leprae, an acid-fast bacillus.
Forms of Disease:
- Tuberculoid Leprosy: Least severe, characterized by nerve damage and sensory loss.
- Lepromatous Leprosy: More severe, causes disfiguring nodules and widespread bacteria dissemination.

Viral Meningitis:
- More common than bacterial, milder symptoms, recovery usually occurs within a week.
- Associated with picornaviruses.
Viral Encephalitis:
- More serious than meningitis, may lead to death/disability.
- Types: Epidemic (often viral arboviruses transmitted by mosquitoes) and sporadic (often HSV-1).

Causative Agents: Polioviruses of the picornavirus family.
Mechanism of Infection: Enters orally (fecal-oral), crosses the blood-brain barrier, and destroys motor nerve cells.
Symptoms: Paralysis and muscle atrophy; post-polio syndrome may occur years later.
Prevention: Via vaccination (Salk and Sabin).

Causative Agent: Rhabdovirus; characterized by meningoencephalitis.
Transmission: Typically through bites; symptoms often mimic other diseases, making diagnosis difficult.
The development of rabies progresses through identifiable stages (incubation, prodromal, acute neurological phase, coma, and death).

Cryptococcal Meningoencephalitis: Caused by Filobasidiella neoformans; often affects immunocompromised individuals.
Naegleria fowleri: A protozoan infection that can enter through nasal mucosa and lead to severe outcomes.

Examples: Creutzfeldt-Jakob Disease, Kuru, Bovine Spongiform Encephalopathy; typically transmitted through ingestion or transplant.
Characteristics: Progressive degeneration of the nervous system, ultimately fatal.