Ch 22: Microbial Diseases of the Nervous System

Helpfulness: 0
Set Details Share
created 2 weeks ago by enl_26
4 views
Subjects:
microbiology
show moreless
Page to share:
Embed this setcancel
COPY
code changes based on your size selection
Size:
X
Show:
1

Central nervous system (CNS)

brain and spinal cord

2

Peripheral nervous system (PNS)

nerves that branch from the CNS

3

Blood–brain barrier

a filtering mechanism of the capillaries that carry blood to the brain and spinal cord tissue, blocking the passage of certain substances.

4

Meningitis

inflammation of the meninges

5

Encephalitis

inflammation of the brain

Whole brain = Encephelon

6

Meningoencephalitis

inflammation of meninges and brain

7

Bacterial Meningitis

  • Initial symptoms of fever, headache, and a stiff neck. Followed by nausea and vomiting
  • May progress to convulsions and coma
  • Death from shock and inflammation
  • Due to endotoxin and cell wall release
  • Viral meningitis is more common and mild
8

Haemophilus influenza Meningitis

  • Gram-negative aerobic bacteria; normal throat microbiota
  • Prevented by the Hib vaccine
  • Accounts for 45% of bacterial meningitis cases; 6% mortality
9

Neisseria meningitidis Meningitis (Meningococcal Meningitis)

  • Gram-negative aerobic cocci with a capsule
  • Mortality of 9–12% with antibiotic therapy; 80% without
  • Outbreaks common in dorms and military barracks
10

Streptococcus pneumoniae Meningitis (Pneumococcal Meningitis)

  • Gram-positive encapsulated diplococcus
  • Also causes pneumonia and otitis media
  • Most common in children (1 month to 4 years)
  • Mortality: 30% in children, 80% in the elderly
  • Prevented by conjugated vaccine
11

Diagnosis and Treatment of the Most Common Types of Bacterial Meningitis

  • Sample CSF via a spinal tap or lumbar puncture
  • Latex agglutination tests
  • Chemotherapy initiated before diagnosis
12

Listeriosis

  • Listeria monocytogenes. Gram-negative aerobic rod
  • Usually foodborne and asymptomatic
  • Can invade the bloodstream, causing sepsis
  • Reproduces in phagocytes. Spread phagocyte-to-phagocyte•Infects pregnant women, crossing the placenta and leading to stillbirth
13

Tetanus

  • Clostridium tetani•Gram-positive, endospore-forming, obligate anaerobe
  • Tetanospasmin (TeNT) – exotoxin released from vegetative cells. Enters CNS. Blocks the relaxation pathway in muscles, causing muscle spasms
  • Death occurs from spasms of respiratory muscles. Lockjaw
  • Prevented by vaccination with tetanus toxoid (DTaP). Stimulates antibodies that neutralize the toxin. Booster required every 10 years
  • Mortality of 25–50%
  • Treatment with tetanus immune globulin (TIG) and Infected tissue removed via debridement
14

Botulism

  • clostridium botulinum: Gram-positive, endospore-forming, obligate anaerobe
  • Intoxication comes from ingesting the botulinal exotoxin (most potent toxin known)
  • Specific for the synaptic end of the nerve. Blocks release of the neurotransmitter acetylcholine, causing flaccid paralysis. Death usually comes from respiratory or cardiac failure
  • Treatment with respiratory assistance and antitoxins (BIG) and Prevented with proper canning and the use of nitrites in foods
15

Leprosy or Hensen's Disease

  • Mycobacterium leprae: Acid-fast rod
  • Grows in peripheral nerves and skin cells.
  • Survives macrophages and invades the myelin sheath
  • Transmission requires prolonged contact with an infected person or the inhalation of secretions
  • Diagnosed with a skin biopsy or skin smear
  • Treatment with antibiotics (Dapsone or Rifampin). Dapsone (inhibits folic acid synthesis similar to sulfonamides)•Rifampin (inhibits bacterial RNA-polymerase)
16

Leprosy

  • Tuberculoid (neural) form
  • Lepromatous (progressive) form
  • loss of sensation in skin areas
  • disfiguring nodules over the body; mucous membranes are affected
17

Poliomyelitis (caused by the poliovirus)

  • Transmitted by the ingestion of water containing feces containing the virus
  • Initial symptoms: sore throat and nausea.
  • Viremia may occur; enters the CNS, destruction of motor cells
  • Death from respiratory failure
  • Postpolio syndrome: muscle weakness occurring decades after infection
  • Salk vaccine (IPV): inactivated vaccine; injectable
  • Sabin vaccine (OVP): attenuated vaccine; oral; lifelong immunity
18

Rabies

  • Enveloped, ssRNA virus. Genus Lyssavirus; bullet shape
  • Usually transmitted by the saliva of an animal bite
  • Can also cross mucous membranes
  • Initial symptoms: muscle spasms of the mouth and pharynx; hydrophobia
  • The virus multiplies in the skeletal muscles and travels through PNS to the brain cells, causing encephalitis
  • Average incubation of 30 to 50 days
19

Rabies Test and vaccines

  • Diagnosed from bodily fluids with the direct fluorescent-antibody (DFA) test
  • Pre-exposure schedule: 3 doses killed virus
  • Post-exposure prophylaxis (PEP): 4 doses of killed virus plus immune globulin
  • Human diploid cell vaccine (HDCV) & Human rabies immune globulin (RIG)
20

Cryptococcus neoformans Meningitis (Cryptococcosis)

  • Soil fungus associated with pigeon and chicken droppings
  • Transmitted by the respiratory route
  • In the immunocompromised, it spreads through blood to the CNS
  • Mortality of up to 30%
  • Treatment: amphotericin B and flucytosine
21

African Trypanosomiasis

  • Trypanosoma brucei gambiense
  • Transmitted from animals to humans by tsetse fly
  • Few early symptoms, followed by fever, headache, and deterioration of the CNS
  • Parasite evades antibodies through antigenic variation
  • Treated with eflornithine: crosses the blood-brain barrier; blocks an enzyme necessary for the parasite
  • Prevention: elimination of tsetse fly vectors
22

Amebic Meningoencephalitis

  • Naegleria fowleri: Causes primary amebic meningoencephalitis (PAM). Protozoan infects the nasal mucosa from swimming water, penetrates the brain, and feeds on brain tissues, “100% fatal”
  • Acanthamoeba: Causes granulomatous amebic encephalitis (GAE). Granulomas form around the site of infection, forming multiple lesions around the brain
23

Nervous System Diseases Caused by Prions

  • Chronic wasting disease
  • Creutzfeldt-Jakob disease (CJD)
  • Kuru
  • Bovine spongiform encephalopathy (BSE)
  • Sheep scrapie