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Microbiology - Introduction > Microbial Diseases of the Nervous System > Flashcards

Microbial Diseases of the Nervous System Flashcards

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1
Q

List the 3 membranes on the meninges

A

Meninges:

  1. Outmost: dura mater
  2. Middle: Arachnoid mater
  3. Innermost: pia mater

Subarachnoid space: in b/w 2 and 3

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2
Q

What is in subarachnoid space? Why is it more vulnerable to bacterial infection?

A
  1. Subarachnoid space is filled with Cerebrospinal Fluid (CSF)
  2. B/c CSF has low levels of antibodies, and few phagocytic cells, bacteria can multiply in it with few checks
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3
Q

Meningitis and Encephalitis

A
  1. Meningitis: an inflammation of the meninges

2. Encephalitis: an inflammation of the brain itself

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4
Q

List the 3 bacterial species that cause more than 70% of the meningitis cases and 70% or the related deaths

Which one is Gram (-), which one is Gram (+), their virulence

A
  1. Haemophilus influenzae: Gram (-)
  2. Neisseria meningitidis: Gram (-)
  3. Streptococcus pneumoniae: Gram (+)

a. They all posses a capsule that protects them from phagocytosis.
b. Gram (+): release cell wall fragments (poptidoglycans and teichoic acids)
c. Gram (-): release endotoxins

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5
Q

Haemophilus influenzae:

  1. Gram property
  2. Diseases
  3. Pathogenicity
A
  1. Aerobic, Gram (-): common member of the normal throat microbiota
  2. Common cause of: meningitis, pneumonia, otitis media and epiglottitis
  3. Pathogenicity due to capsular antigens of type b.; mostly in children under 4 yr old
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6
Q

Neisseria meningitidis

  1. Gram property
  2. Diseases
  3. Pathogenicity
  4. Most distinguishing feature
  5. Residual damage after infection
A
  1. Aerobic, Gram (-): common member of the normal nose and throat microbiota (10% of the population)
  2. Meningococcal meningitis;
  3. Pathogenicity due to capsule (endotoxin)
  4. Most distinguishing feature: a rash that doesn’t fade when pressed.
  5. Deafness; Gram (-) sepsis
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7
Q

Treatment of the most common types of bacterial meningitis

A
  1. Broad-spec. third gen. Cephalosporins are usually used before identification of the pathogen is complete
  2. Once confirmed, antibiotic treatment may be changed
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8
Q

Diagnosis of bacterial meningitis

A
  1. Sampling of CSF

a. Latex agglutination test

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9
Q

Listeria monocytogenes

  1. Gram property
  2. Virulence
A
  1. Gram (+) rod

2. When ingested by phagocytic cells, it is not destroyed; it proliferantes w/i them, primarily in the liver.

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10
Q

Tetanus

  1. Etiology
  2. Toxin
  3. Signs and Symptoms
A
  1. Caused by Clostridium tetani: obligately anaerobic, endospore-forming, Gram (+) rod
  2. Neurotoxin: tetanospasmin – released upon death and lysis of the growing bacteria. It enters the CNS via peripheral nerves or blood.
    a. The toxin blocks the relaxation pathway, resulting in muscle spasms
    b. Muscles of the jaw are affected early in the disease – Lockjaw
  3. Lockjaw, Opisthotonos
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11
Q

Death resulting from Tetanus

A
  1. Due to spasms of the respiratory muscles
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12
Q

Vaccination for Tetanus

A
  1. Toxoid: an inactivated toxin that stimulates the formation of antibodies that neutralize the toxin produced by the bacteria
  2. Tdap
  3. Booster is required every 10 years
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13
Q

Tetanus Immune Globulin (TIG)

A
  1. Prepared from the antibody-containing serum of immunized humans to provide temporary immunity to patents who do not have immunity
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14
Q

Poliomyelitis

  1. Virus
  2. Signs and Symptoms
  3. Mode of transmission
A
  1. Poliovirus - less than 1% of the infected cause paralysis
    a. In infants: while still protected by maternal antibodies, usually asymptomatic poliomyelitis and can develop immunity
    b. Adolescence or early adulthood: paralytic form of the disease occurs more frequently
  2. Great majority of infections are asymptomatic or exhibit only mild symptoms: headache, sore throat, fever, and nausea.
  3. Mode of transmission: polioviruses are more stable than most other viruses and can remain infectious for relatively long periods in water and food. The primary mode of transmission is ingestion of water contaminated w/ feces containing the virus
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15
Q

How does poliovirus affect the CNS

A
  1. When the virus invades the tonsils and the lymph nodes of the neck and ileum, from the lymph nodes, the virus enters the blood, resulting in Viremia.
  2. Usually, Viremia is only transient. If the Viremia is persistent, the virus penetrates the capillary walls and enters the CNS
  3. Once in the CNA, the virus displays a high affinity for nerve cells, particularly motor nerve cells in the upper spinal cord.
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16
Q

Poliomyelitis

  1. Virus
  2. Signs and Symptoms
  3. Mode of transmission
A
  1. Poliovirus - less than 1% of the infected cause paralysis
    a. In infants: while still protected by maternal antibodies, usually asymptomatic poliomyelitis and can develop immunity
    b. Adolescence or early adulthood: paralytic form of the disease occurs more frequently
  2. Great majority of infections are asymptomatic or exhibit only mild symptoms: headache, sore throat, fever, and nausea.
  3. Mode of transmission: polioviruses are more stable than most other viruses and can remain infectious for relatively long periods in water and food. The primary mode of transmission is ingestion of water contaminated w/ feces containing the virus
17
Q

How does poliovirus cause paralysis

A

When the virus multiplies w/i the cytoplasm of the motor nerve cells, the cells dies, and paralysis results. Death can result from respiratory failure.

18
Q

Poliovirus vaccines:
1. Salk vaccine
2.

A
  1. Salk vaccine: inactivated polio vaccines (IPV); NOW E-IPV (Enhanced-IPV)replaces the original IPV in the US
    a. Viruses are inactivated by treatment w/ formalin
    b. Vaccine effectiveness rate is as high as 90%; antibody levels decline w/ time, and booster shots are needed every few years to maintain full immunity
  2. Sabin vaccine: contains 3 living, attenuated strains of the virus
    a. AKA. oral polio vaccine, or OPV.
    b. 1 in 750,000 first doses, 1 in 2.4 million on subsequent doses, one of the attenuated strains of the excreted virus may revert to virulence and transmit the disease.
  3. In 2000, the CDC decided that the advantages of the OPV no longer outweight the risks. So, only use IPV for the routine immunization of children.
19
Q

Poliovirus vaccines:

  1. Salk vaccine
  2. Sabin vaccine
A
  1. Salk vaccine: inactivated polio vaccines (IPV); NOW E-IPV (Enhanced-IPV)replaces the original IPV in the US
    a. Viruses are inactivated by treatment w/ formalin
    b. Vaccine effectiveness rate is as high as 90%; antibody levels decline w/ time, and booster shots are needed every few years to maintain full immunity
  2. Sabin vaccine: contains 3 living, attenuated strains of the virus
    a. AKA. oral polio vaccine, or OPV.
    b. 1 in 750,000 first doses, 1 in 2.4 million on subsequent doses, one of the attenuated strains of the excreted virus may revert to virulence and transmit the disease.
  3. In 2000, the CDC decided that the advantages of the OPV no longer outweight the risks. So, only use IPV for the routine immunization of children.
20
Q

Rabies

  1. Disease
  2. Incubation period
A
  1. Almost always results in fatal encephalitis
    a. Humans usually acquire the rabies virus from the bite of an infected animal. Rabies virus can also be present in aerosols.
  2. Incubation period: long enough to allow immunity to develop from postexposure vaccination. – usually 30-50 days
    a. The virus remains localized for periods ranging from days to months. Then it enters and travels, at the rate of 15-100 mm/day, along PNS to CNS, where it causes encephalitis.
21
Q

Rabies

  1. Sign and symptoms
  2. Diagnosis of rabies virus
  3. Treatments
A
  1. Spasms of mouth, and throat muscles followed by extensive brain and spinal cord damage and death.
  2. Immunofluorescence studies of saliva, serum; or cerebrospinal fluid // fluorescent-antibody test performed on brain tissue
  3. Treatments: postexposure treatment includes administration of human rabies immune globulin (RIG) along w/ multiple intramuscular injections of vaccine.
22
Q

Arboviral Encephalitis

  1. Signs and symptoms
  2. Etiology
A
  1. S&S: chills, headache, fever and eventually coma

2. Many types of viruses transmitted by mosquitoes, causing encephalitis (Arbovirus: short for arthropod-borne virus)

23
Q

Cryptococcosis

  1. Causative agent
  2. Reservoir of microorganism
  3. Signs and symptoms
  4. Diagnosis method
  5. Drugs
  6. Mortality rate
A
  1. Causative agent: Cryptococcus neoformans; an encapsulated yeastlike fungus
  2. Widely distributed in soil, esp. soil contaminated w/ pigeon droppings.
  3. Inhalation of C. neoformans (in dried infected pigeon or chicken droppings), causing infection of the lungs. Sometimes, it can spread through the bloodstream to the brain and meninges, esp. in immunosuppressed individuals. The disease is usually expressed as chronic meningitis
  4. Diagnosis: latex agglutination test to detect cryptococcal antigens in serum or cerebrospinal fluid
  5. Amphotericin B and Flucytosine in combination.
  6. Mortality rate: 30%
24
Q

African Trypanosomiasis

  1. Etiology
  2. Signs and symptoms
  3. Drugs
A
  1. aka. sleeping sickness. Caused by Trypanosoma brucei gambiense and Trypanosoma brucei rhodesiense, flagellates that are injected by the bite of a tsetse fly.
25
Q

Naegleria Meningoencephalitis

  1. Etiology
  2. Signs and symptoms
  3. Fatality rate
A
  1. Etiology: Naegleria fowleri, a protozoan that causes the neurological disease
  2. Initially infects the nasal mucosa andd later proliferates in the brain.
    a. The most common victims are children who swim in ponds or streams.
  3. The fatality rate is nearly 100%, diagnosis is typically made at autopsy.
26
Q

Streptococcus pneumonia Meningitis

  1. Causative agent
  2. Who are more susceptible to the disease?
A
  1. Caused by S. pneumonia; commonly found in the nasopharynx

2. Hospitalized patients and young children are most susceptible to S. pneumoniae meningitis.

27
Q

Treatment of the most common types of bacterial meningitis

A

Cephalosporins may be administered before identification of the pathogen

28
Q

Who are more susceptible to Listeriosis

A

Listeria monocytogenes causes meningitis in newborns, the immunosuppressed, pregnant women and cancer patients.

Microbiology - Introduction (33 decks)

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