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Biology 9700 > Infectious Diseases > Flashcards

Infectious Diseases Flashcards

1
Q

What is a disease?

A

Illness or disorder of the body or mind that leads to poor health.

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2
Q

What is an infectious disease?

A

A disease caused by an organism called a pathogen.

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3
Q

What is a pathogen?

A

A disease-causing organism

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4
Q

Why are infectious disease also called communicable diseases?

A

They can be passed from infected person to uninfected person.

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5
Q

What is disease transmission?

A

The transfer of a pathogen from an infected person to an uninfected person.

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6
Q

What are disease carriers?

A

Individuals that have a pathogen but are symptomless but still have the potential to spread the pathogen.

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7
Q

What is a transmission cycle?

A

The passage of a pathogen from one host to another and it is repeated as the pathogen infects a new host.

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8
Q

Give examples of control methods to break transmission cycles.

A
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9
Q

What is disease eradication?

A

The complete breakage of a transmission cycle of a pathogen so that there are no more cases of the disease anywhere in the world.

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10
Q

What are endemic diseases?

A

Diseases that always exist in a population

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11
Q

What pathogen causes cholera?

A

Vibrio Cholerae

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12
Q

Causes of cholera?

A
  1. Poor sanitation
  2. An infected person with the pathogen handling food or utensils without washing their hands
  3. Contaminated food or water supplies
  4. Use of raw human sewage to irrigate vegetables in areas where clean adequate water is unavailable
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13
Q

What is the site of action of Vibrio Cholerae and what results if it gets there?

A

The site of action is the small intestine. It has to pass through the stomach and the bacteria may be killed by the acidic conditions in the stomach. If it survives then it makes it to the small intestine where it then releases a toxin called choleragen which disrupts the function of the epithelial lining in the small intestine, causing salts and water to move out of the blood into the small intestine to then be released in the form of watery faeces which contains the pathogens.

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14
Q

How is cholera treated?
State the importance of this.

A
  1. If the person can drink then it is given in the form of an oral rehydration therapy which contains glucose and water. Glucose is important as it is absorbed by the blood and is linked to the uptake of sodium and potassium. Water is good as the fluid intake is supposed to be equal to the fluid loss to maintain the osmotic balance of the blood and the tissue fluids.
  2. If the person cannot drink then oral rehydration therapy is given intravenously.
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15
Q

How can cholera be prevented?

A
  1. Vaccination for cholera in areas where it is endemic
  2. Provision of clean piped water which is chlorinated to kill bacteria
  3. Provision of adequate sewage treatment infrastructure
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16
Q

Why is it difficult to control and prevent cholera?

A
  1. The inability of governments to fund the provision of sewage treatment infrastructure, proper drainage infrastructure and good piping systems in fast growing cities as they are also looking to fund other important projects in the city’s growth
  2. Use of raw human sewage to irrigate crops in areas where water is unavailable
  3. Human crises which cause displacement of individuals and result in destroyed sanitation facilities
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17
Q

What are the four species of Plasmodium that cause malaria?

A
  1. Plasmodium falciparum
  2. Plasmodium malariae
  3. Plasmodium ovale
  4. Plasmodium vivax
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18
Q

What is the disease vector for malaria?

A

The female anopheles mosquito

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19
Q

How may malaria be transmitted?

A
  1. Female anopheles mosquito biting an uninfected person after coming from biting an infected person.
  2. Blood transfusion
  3. Injecting using unsterilised needles
  4. The pathogen may pass through the placenta
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20
Q

What happens when a female anopheles mosquito bites an infected person and when it then bites an uninfected person?

A

It bites humans to get protein in their human blood meal for the development of their eggs. Plasmodium’s gametes are present in their blood meal and these fuse and develop to form infective stages in the gut of the mosquito. These then move to the mosquito’s salivary glands. When the mosquito bites an uninfected person it releases an anticoagulant so that blood flows into the mosquito well. The infective stages pass into the person. The parasites enter the red blood cells where they multiply.

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21
Q

Why is transmission more intense in places where mosquitoes have a longer lifespan?

A

The pathogen is given more time to complete its development in the mosquito.

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22
Q

What is used to treat for malaria?

A

Antimalarial drugs such as quinine and chloroquine

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23
Q

What are prophylactics?

A

Preventative drugs

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24
Q

Which two prophylactics are used for malaria?

A

Chloroquine
Proguanil

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25
Q

What does chloroquine do?

A

It is a prophylactic for malaria that inhibits protein synthesis and prevents the spread of the parasite in the body.

26
Q

What does proguanil do?

A

Inhibits the sexual reproduction of plasmodium

27
Q

What is the best available treatment for malaria?

A

Artemisinin-based combination therapy (ACT) where drugs derived from Artimisia annua are used in combination with other drugs like mefloquine to treat infections.

28
Q

How do we control malaria?

A
  1. Improving diagnosis of disease
  2. Improving supply of effective drugs
  3. ACT
29
Q

How do we reduce malaria?

A
  1. Prophylactics
  2. Reducing chances of being bitten
  3. Reducing the number of female anopheles mosquito
30
Q

How can we reduce the number of mosquito?

A
  1. Putting oil on water bodies so that mosquito larvae cannot breathe
  2. Draining marshes and wetlands
  3. Clearing vegetation
  4. Spraying living areas with insecticides
31
Q

Give some biological control methods of malaria.

A
  1. Permanent water bodies that contain mosquito-eating fish
  2. Spraying a preparation which kills mosquito larvae but is not toxic to other forms of life
32
Q

How do you prevent getting bitten?

A

Mosquito nets
Repellent

33
Q

What kind of test for malaria is faster?

A

Simple dip stick tests

34
Q

What virus causes HIV/AIDS

A

Human immunodeficiency virus

35
Q

What kind of virus is HIV? What does this mean?

A

A retrovirus. Its genetic material is RNA and not DNA

36
Q

What is the effect of the virus on the immune system?
How does this occur?

A

The virus attacks the body’s T-helper lymphocytes which control the immune system’s response to infection. As they become lower in number, the immune system loses defence and becomes weaker, making the individual prone to opportunistic infections.
The viral RNA is injected into the T-helper lymphocytes and with the help of reverse transcriptase the RNA is converted to DNA and is incorporated into the DNA of the host. It then begins to express viral proteins.

37
Q

What are opportunistic infections?

A

An infection caused by pathogens that take advantage of a host with a weakened immune system.

38
Q

How is HIV transmitted?

A
  1. Sharing of needles among injecting drug users
  2. Blood donation
  3. Unprotected sexual intercourse
  4. Through the placenta
  5. At birth when there is mixing of blood
  6. Through breast milk
39
Q

What are the adverse effects of HIV/AIDS on the economy?

A
  1. Usually affects the economically active group
  2. Strains government funds in buying expensive drugs
40
Q

What drug is used to treat HIV/AIDS? What does it do?

A

Zidovudine. It binds to the viral enzyme reverse transcriptase and blocks its action, stopping the replication of the viral genetic material and results in an increase in the body’s lymphocytes

41
Q

Why is HIV difficult to control?

A

It has a long latent stage so that means some individuals may be HIV+ but not know it because they are symptomless

42
Q

Why is it difficult for the body to recognise the virus or for the development of a vaccine?

A

The virus’ surface proteins are always changing

43
Q

How to prevent HIV?

A
  1. Screening blood donations
  2. Contraception
  3. Educating on the disease
  4. Encouraging drug users to give up their habit
  5. HIV+ mothers are given antiretroviral drugs
44
Q

How to control HIV?

A
  1. Contract tracing
  2. Needle exchange schemes
  3. Antiretroviral drugs
  4. Widespread testing of the population
45
Q

What two pathogens cause TB?

A
  1. Myobacterium tuberculosis
  2. Myobacterium bovis
46
Q

How is TB spread?

A
  1. Coughing publicly
47
Q

Increase in TB is because of?

A
  1. Drug resistant strains
  2. HIV/AIDS pandemic
  3. Poor housing and homelessness
48
Q

How is TB treated?

A

Infected person is isolated in their most infectious stage. They are given many drugs in combination to kill the bacteria and reduce chance of resistance. They may also be put under DOTS to ensure they take their medication and complete their course.

49
Q

What drugs are usually used?

A

Isoniazid
Rifampicin

50
Q

What causes drug resistance?

A

Mutation in the bacterial DNA

51
Q

What are the consequences of antibiotic resistance?

A
  1. We exert greater selection pressure on bacteria to evolve resistance the more we use them
  2. There is an increased chance of severity and death because this is usually associated with long hospital stays
  3. Where there is frequent use of antibiotics there is a quick spread of the resistance among bacteria
  4. Bacteria living where there is widespread use of antibiotics may acquire resistance to many of the different antibiotics, resulting in multiple resistance.
52
Q

What antibiotic is used for MRSA?

A

Vancomycin

53
Q

How can we reduce the impact of antibiotic resistance?

A
  1. Antibiotics should be carefully chosen so that only the most effective one can be used for the infection
  2. A bacterium resistant to a particular antibiotic is not resistant to the same antibiotic with a different chemical structure
  3. Encourage patients to complete their courses of antibiotic treatment
  4. Make sure that patients do not keep unused antibiotics to be used later or used by someone else
  5. Avoiding the use of wide spectrum antibiotics and using the antibiotic for the specific infection
  6. Reducing the number of countries in which antibiotics are sold without prescription.
  7. Avoiding the use of antibiotics on farms to prevent, rather than cure, infections
54
Q

How are the genes for antibiotic resistance transferred?

A

Through conjugation where a tube forms between the two bacteria and there is transfer of the plasmids or part of the DNA to the recipient bacterium.

55
Q

What gene has bacteria resistant to penicillin acquired?

A

The gene that codes for the enzyme B-lactamase which breaks down the structure of penicillin

56
Q

How does penicillin work?

A

Penicillin inhibits the action of the enzyme responsible for the formation of cross-links between peptidoglycan chains in the cell wall. The cell wall secretes autolysins which punch holes in the cell wall, allowing it to stretch enough for these cross-links to form. Since penicillin is inhibiting the enzyme that forms these cross-links, more holes are punched into the cell wall until a point where osmotic balance is unstable the bacterial cell eventually bursts.

57
Q

What is antibiotic resistance?

A

The ability of bacteria to grow in the presence of an anitbiotic that would usually slow its growth or kill it.

58
Q

What resistance mechanisms may bacteria have to antiobiotics?

A

-Some may have proteins that are able to pump out the antibiotics if they enter the cytoplasm
-Some antibiotics may be unable to bind to the sites on the cell membrane
-Some have proteins that in the membrane that can deactivate antibiotics so they have no effect
-Some have a gene that codes for the enzyme that catalyses the breakdown of the antibiotic.

59
Q

Why don’t antibiotics affect viruses?

A

-Viruses don’t have their own metabolism but use that of their host cell
-Have a protein coat rather than a murein cell wall
-Have very few organells so there a few sites for antibiotics to work on
-Viruses live inside host cells, far out of the reach from antibiotics

60
Q

What do we call antibiotic resistance passed on from one generation to the next?

A

Vertical gene transmission

61
Q

What do we call antibiotic resistance passed from one bacteria to another of the same or different species via conjugation?

A

Horizontal gene transmission

Biology 9700 (4 decks)

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