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Nervous System Infections

Nervous System Infections. Chapter 20. Nervous system. Central nervous system (CNS) Brain Encephalitis Spinal cord Peripheral nervous system (PNS) Bundles of thin extensions from nerve cells called axons. Two basic cell types Neuroglia Provide support Neurons Carry nerve impulses

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Nervous System Infections

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  1. Nervous System Infections Chapter 20

  2. Nervous system • Central nervous system (CNS) • Brain • Encephalitis • Spinal cord • Peripheral nervous system (PNS) • Bundles of thin extensions from nerve cells called axons

  3. Two basic cell types • Neuroglia • Provide support • Neurons • Carry nerve impulses • Nucleus in the cell body • ganglion

  4. Defenses • Meninges • Meningitis • Cerebrospinal fluid (CSF) • Bone casing • Blood-brain barrier

  5. Structures of brain and spinal cord

  6. Normal flora • None • Viruses can exist in a dormant state in the nervous system • penetrate CNS by traveling up nerve bundles • Herpes simplex and rabies viruses

  7. Bacterial Meningitis • Pathogens and virulence factors • Streptococcus pneumoniae – leading cause in adults • Neisseria meningitidis – epidemic, fimbriae, capsule, and endotoxin • Haemophilus influenzae – leading cause prior to vaccine • Listeria monocytogenes –listeriosis infetuses, pregnant women, and immunocompromised individuals • Streptococcus agalactiae – causes most cases of newborn meningitis

  8. Neisseria Streptococcus

  9. Haemophilus Listeria

  10. Signs and symptoms • Acute high fever and severe meningeal inflammation • Inflamed cranial meninges – severe headache, vomiting, pain • Inflamed spinal meninges – stiff neck, altered muscle control • Encephalitis may cause behavioral changes, coma, and death • Petechiae may appear on skin

  11. Epidemiology • S. agalactiae acquired during birth • Listeria transmitted via contaminated food • S. pneumoniae, Neisseria & Haemophilusall transmitted via respiratory droplets • S. pneumoniae present in throat of 75% of humans without causing harm • Meningococcal meningitis is the only form that becomes epidemic

  12. Diagnosis • Based on symptoms and culturing of bacteria in CSF from spinal tap

  13. Prevention • Vaccines available for S. pneumoniae, H. influenzae, and N. meningitidis • Individuals at risk for listeriosis should avoid high-risk foods (milk, cheeses, undercooked meat) • Mass prophylaxis with ceftriaxone or rifampin helps control epidemics of meningococcal form • Treatment • ceftriaxone or penicillin

  14. Tetanus • “Lockjaw” • Causative agent • Clostridium tetani • Anaerobic • Gram positive • Bacillus • Spore former

  15. Signs & Symptoms • Tightening of jaw and neck muscles • difficulty swallowing • Restlessness and irritability • Increased contractions spreading to other muscles • Back spasms • Difficulty breathing and death • Prolonged contraction of diaphragm

  16. Bacteria contained to anaerobic tissue around wound • Tetanospasmin toxin moves to CNS and blocks inhibition of motor neurons causing paralysis • 50-90% mortality rate in untreated cases

  17. Epidemiology • C. tetani found in dirt and dust and GI tract of humans and other animals • Nearly half of infections result from puncture wounds including • Body piercing, tattooing, animal bites, IV drugs • Frequently fatal but rare in the developed world • 30 to 60 cases reported in US annually

  18. Prevention • Immunization with toxiod vaccine • DTaP • Treatment • Thoroughly clean wound • Remove all dead tissue and foreign material • Penicillin to kill multiplying bacteria • Will not destroy endospores • Antitoxin • Neutralizes only circulating toxin

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