Microbiology- Chapter 19 ( Infectious Diseases Affecting The Nervous System)

Front 1

What are the two parts of the nervous system.

Back 1

Divided into two parts:

Central Nervous System (CNS)
-Brain and spinal cord

Peripheral Nervous System (PNS)
-Nerves that transfer commands between the CNS and muscles and glands
-Sensory nerves- carry signals towards the CNS
-Motor nerves- carry signals away from the CNS
-Mixed nerves- carry signals both toward and away from the CNS

Front 2

The brain and spinal cord are covered with three membranes called the? Describe these membranes.

Back 2

meninges

-Dura matter – outermost membrane
-Arachnoid – middle membrane
-Pia meter innermost membrane
-Between arachnoid and pia mater there is a space that is filled with a fluid- cerebrospinal fluid in which bacteria can multiply

Front 3

True or false.

The CNS has normal biota.

Back 3

FALSE

-CNS is an axenic environment
-It has no normal microbiota
-Restricted permeability of blood vessels

Front 4

How do pathogens enter the nervous system?

Back 4

-Pathogens may access the CNS:
-Breaks in the bones and meninges
-Medical procedures
-Traveling through peripheral neurons to the CNS

Front 5

What is meningitis? What causes it?

Back 5

An inflammation of the meninges.

-An infection of the membranes – meningitis

-Can be caused by
-Bacteria
-Streptococcus pneumonia
-Haemophylus influenza
-Neisseria meningitides
-50 other species of bacteria
-Viruses
-Fungi
-Protozoa

-An infection of the brain – encephalitis

Front 6

What are the two ways bacteria can cause disease of the nervous system?

Back 6

Infect cells of the nervous system
-Meningitis
-Leprosy

Bacteria growing elsewhere release toxins that affect neurons
-Botulism
-Tetanus

Front 7

What are the sign and symptoms of bacterial meningitis?

Back 7

-Signs and Symptoms

-Sudden high fever and severe meningeal inflammation

-Inflamed cranial meninges; severe headache, vomiting

-Inflamed spinal meninges: stiff neck, altered muscle control

-Infection of the brain, or encephalitis, can result in behavioral changes, coma, and death

-Signs and symptoms may develop rapidly

Front 8

What is an infection of the brain called?

Back 8

encephalitis

Front 9

What is Heamophilus influenzae?

and..
-what does it cause?

Back 9

-Gr negative bacteria, normal throat microflora

-Causes meningitis in children (6 months to 4 years old)

-Of all bacterial meningitises H. influenza accounts for most often causes

-Existing vaccine

Front 10

What is Neisseria meningitidis?

Back 10

-Gram negative cocci (meningococcus)

-Normal microbiota in the nose and throat

-Begins as a throat infection

-Replicate in blood and eventually enter cerebrospinal fluid

-The cells are surrounded by thick capsules that protect them from phagocytosis

-Produces endotoxin that can cause death in few hours

-Vaccine available – not for all serotypes

-Treatment: Intravenous injection of antibiotic (Penicillin G) – as soon as possible

Front 11

Describe Streptococcus pneumoniae and what it causes.

Back 11

- Gram positive diplococcus

-Causes pneumococcal meningitis in children (1 month to 4 years old).

-It is a common flora of the mouth and throat. It also causes pneumonia and ear infections

-Mortality rate high (30% in children and 80% in the elderly)

-Vaccine available, recommended for infants under the age of 2

Front 12

Describe Listeriariosis

_ Cause
_ Effects
_ Treatment

Back 12

-Causative agent: Listeria monocytogenes (gr+ rods)

-Infects animals and humans

-Source of infection: ingestion of contaminated food (dairy products, meat..)

-Affects:
-Adults with compromised immune system

-Pregnant women especially susceptible

-Fetus infected through placenta
(abortions, and stillbirths)

-Newborns infected through the birth canal

-Grows in central nervous system of placenta

-Treatment: Penicillin G

Front 13

Describe fungal meningitis.

Important: What its caused by.

Back 13

-Fungi rarely infect the CNS
-Cryptococcosis – fungal meningitis
-Caused by the Cryptococcus neoformans- a yeast
-Found in soil and pigeon droppings
-Infection via inhalation
-Mycoses may spread from the lungs to the CNS via the blood
-Affects especially AIDS patients

Front 14

Describe Naegleria meningoencephalitis

Back 14

-Caused by Naegleria fowleri – amaeba.
-The victims are children who swim in ponds and streams
-The pathogen infects the nasal mucous membrane and then the brain
-The disease is fatal (100%).

Front 15

Describe Arboviral Encephalitis

Back 15

-Arboviruses are arthropod-borne viruses

-The virus is transmitted by mosquito to humans and horses

-Proliferation of the disease occurs during summer months

-Symptoms; Chills, fever, headache, and even death,

-Different forms of encephalitis: Western equine encephalitis, Eastern equine encephalitis, St. Luis encephalitis, California encephalitis, Japans B encephalitis

Front 16

describe West Nile Virus

Back 16

-A new arbovirus disease

-Infects birds and humans

-Symptoms:
-Body aches, headache, Polio-like paralysis, and fatal encephalitis (especially in elderly)

-Treatment: alleviate symptoms

-Prevention involves limiting contact with mosquitos
-Use netting and insect repellants
-Reduce mosquito numbers by eliminating stagnant water

Front 17

What are prions?

Back 17

-Prions are infectious proteins

Front 18

what do prions cause?

Back 18

-They cause spongiform degeneration of the brain – transmissible spongiform encephalitis

-Abnormally folded prion proteins – transform the normal protein
-Unclear why the initial prion misfolds

-Prion disease include Sheep scrapie, mad cow disease, and variant Creutzfeldt-Jakob disease

Front 19

Describe Creuzfeldt- Jacob disease

Back 19

-Symptoms: altered behavior, dementia, memory loss, senility

-Not communicable disease

-Some transmission is possible:
-Transplants
-Contaminated surgical instruments
-Injection of growth hormones from infected pituitary glands

-Genetic mutation

Front 20

Describe sheep scrapies.

Back 20

-Symptoms; The infected animal scrapes itself against the wall. Loss of motor control- death

-*incase of* Mad cow disease- the animals must be destroyed

Front 21

What causes rabies and how does it enter the nervous system?

Back 21

-Caused by rabies virus (rhabdovirus)

-Acquired by the bite of an infected animal (also transmitted by aerosol)

-After infection the virus multiplies in skeletal muscles (up to few months)

-Then the virus enters the peripheral nerves through which it travels into central nervous system

Front 22

Describe Rabies.

Back 22

-Symptoms: spasm of muscles, hydrophobia, biting behavior, excitability, increased salivation, difficulties in swallowing. Damage to nervous system- death.

-Diagnosis: immunofluorescent detection of viral antigens in saliva or brain tissue (dead animal)

-Reservoir of infection: dog, cat, skunk, bat, fox, raccoon.

-Treatment: 5-6 injection of vaccine + rabies immune globulin

-Prevention: Vaccination of dogs and cats

Front 23

what causes Poliomyelitis (Polio)?

Back 23

-Caused by polyovirus

Front 24

Describe Poliomyelitis (Polio)

Back 24

-The infection is initiated with ingestion of the virus (contaminated water)

-Disease starts with the mild symptoms (fever, soar throat, nausea)

-Primary area of infection is throat and small intestine. Next, tonsils, lymph nodes, blood and central nervous system
-Virus multiples in the motor nerve cells
-Cell dies

-Severe symptoms: 1% of infected will suffer from paralysis

Front 25

What are the two types of vaccines available for polio?

Back 25

-Salk vaccine – used in Europe

-Sabin vaccine – more popular in the U.S.

Front 26

Describe the salk vaccine.

Back 26

For Polio
-Salk vaccine – used in Europe

-Viruses inactivated with formation
-Must be injected
-Booster required

Front 27

Describe the sabin vaccine.

Back 27

For polio

-Sabin vaccine – more popular in the U.S.
-Living attenuated viruses (virus is not killed)
-Disadvantage – may cause disease
-*Advantage* Lifelong immunity *and booster is not required*

Front 28

What causes tetanus?

Back 28

Caused by Clostridium tetani = anaeorobic, endospore forming gr+ rod

Front 29

How is tetanus contracted?

Back 29

-Contracted by infection of the wound with rusty nails. Clostridium is found in the soil contaminated with animal feces.

Front 30

What are the sign/symptons of tetanus and the incubation period?

Back 30

-Signs/Symptoms: Tightening of the jaw and neck muscles, followed by fever and muscle spasms

-Incubation period: Five days to fifteen weeks

Front 31

Describe how tetanus occurs.

Back 31

-Clostridium spores enter a host through a wound on the skin and then it replicates

-Produces tetanospasmin toxin blocks the release of neurotransmitters

-Toxin is:
-taken up into the nerve axon and transported to the central nervous system
-fixed to the inhibitory motor nerve endings- blocking the inhibitory impulses

-The bacterium produces a potent neutroxin that causes uncontrollable muscle contractions – muscle spasms

-Cause of death – spasm of respiratory muscles.

Front 32

What is the treatment and prevention of tetanus?

Back 32

-Treatment: Human tetanus immunoglobulin penicillin

-Prevention: Vaccination with tetanus toxoid (DTP)

Front 33

What causes botulism?

Back 33

Caused by Clostridium botulism

Front 34

What is the treatment for botulism?

Back 34

-Treatment; antitoxin therapy

Front 35

How do people get botulism?

Back 35

-Not transmitted from person to person
-Source of infection: home processed foods, vegetables, fruits, meat, fish
-Spores can survive at high temperature

Front 36

How does botulism affect the body?

Back 36

-Clostridium produces exotoxin (botulinum toxin) – the most poisonous naturally occurring substance- the lethal dose is 1ng/kg

-The toxin blocks the release of acetylcholine

-Therefore the muscle remains relaxed – flaccid paralisis

Front 37

Describe infant botulism.

Back 37

Infant Botulism

-Infants do not have established normal microflora – infant botulism

-Cases reported with honey
-should not be given to infants under 1 year of age

Front 38

What causes African trypanosomiasis – sleeping sickness and how is it transmitted?

Back 38

Protozoa

-Caused by Trypanosoma brucei gambiense.

-It is transmitted by the bite of tsetse fly

Front 39

Describe Sleeping Sickness

Back 39

-In early stage the protozoa is found in low numbers in the blood (2-4 years).

-In later stage the pathogen moves to central nervous system

-Symptoms; decrease in physical activity and mental acuity, coma, and death.

-Difficulty in developing vaccine – the parasite changes the protein coat

-Prevention: eliminating tsetse flies

Front 40

What is the treatment for Sleeping sickness?

Back 40

-Treatment:

-At early stage: suramin
-Late stage (brain infected) arsenic-based drug