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

7. 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

8. 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 in fetuses, pregnant women, and immunocompromised individuals – Streptococcus agalactiae – causes most cases of newborn meningitis Bacterial Meningitis

9. Streptococcus Neisseria

10. Haemophilus Listeria

11. 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

12. Epidemiology S. agalactiae acquired during birth Listeria transmitted via contaminated food S. pneumoniae, Neisseria & Haemophilus all 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

13. Diagnosis – Based on symptoms and culturing of bacteria in CSF from spinal tap

14. 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

15. Tetanus “Lockjaw” Causative agent – Clostridium tetani Anaerobic Gram positive Bacillus Spore former

16. 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

17. 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

18. 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

19. 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