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ESA1 > Infection and Microbiology > Flashcards

Infection and Microbiology Flashcards

1
Q

What types of tissues are mostly sterile? (Little interaction with microbes?)

A
  • Muscle tissue
  • Nervous tissue
  • Connective tissue
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2
Q

When looking at a slide of epithelial cells stained with H&E, why can we not see the bacteria/archaea that must be present?

A
  • They stain poorly with H&E
  • Tissue preparation (deliberately) removed many of them
  • Insufficient magnification
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3
Q

What is the most commonly used stain to detect and classify bacteria?

A

Gram stain

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4
Q

Which 2 diseases are caused by bacteria that cannot be stained using the Gram method?

A

1) Tuberculosis

2) Leprosy

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5
Q

What can be used instead of the Gram method to detect tuberculosis/leprosy-causing bacteria?

A

Acid-fast stains

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6
Q

Which 2 staining methods are used everyday to detect and classify bacteria?

A

1) Gram stain

2) Acid-fast stains

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7
Q

What charge is Crystal Violet?

A

Positively charged

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8
Q

Why does Crystal Violet bind to DNA during Gram staining?

A

Positively charged Crystal Violet binds to negatively charged DNA

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9
Q

Why is Iodine added during Gram staining?

A

Iodine forms large molecular complexes with the Crystal Violet (previously added), which cannot be removed from Gram-positive cell wall.

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10
Q

What are the four components to a Gram stain, in order?

A

1) Crystal violet
2) Iodine
3) Acetone/Methanol
4) Red counterstain ie Safranin

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11
Q

If a bacterium appears violet/purple after Gram staining, what does this mean and why?

A

The bacterium is Gram-positive, meaning it has a thick peptidoglycan-rich cell wall which has retained the crystal violet-iodine complexes

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12
Q

If a bacterium appears red/pink after Gram staining, what does this mean and why?

A

The bacterium is Gram-negative, meaning it has a thin cell wall containing little peptidoglycan, which allowed the alcohol to wash out the crystal violet-iodine complexes, and was then stained with the red counterstain.

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13
Q

Which type of bacteria have thick peptidoglycan-rich cell walls, and which staining method can you use to determine this?

A

Gram-positive, using the Gram staining method

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14
Q

Which type of bacteria have thin cell walls with little peptidoglycan, and which staining method can you use to determine this??

A

Gram-negative, using the Gram staining method.

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15
Q

What is the use of Gram staining?

A

It determines certain properties of bacteria cell walls (peptidoglycan amount), and allows classifcation

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16
Q

Name the 3 possible shapes of a bacterium:

A

1) Rods/bacilli
2) Cocci
3) Coccobaccili

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17
Q

What are the 2 types of internal structures within a bacteria?

A

1) Spores

2) Internal granules

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18
Q

What does the presence of a spore within a bacterium indicate?

A

The bacteria is able to enter a state of dormancy, which is highly resistant to treatment

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19
Q

What are the 3 possible external structures of a bacterium?

A

1) Pilli/fimbriae
2) Flagellae
3) Capsule

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20
Q

What type of bacteria do not contain peptidoglycan within their cell envelope?

A

Mycoplasmas

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21
Q

What is an acid-fast bacillus?

A

A type of bacillus that resists decolorizing by acid after accepting a stain.

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22
Q

Give 2 examples of acid-fast bacilli:

A

1) Mycobacterium tuberculosis

2) Mycobacterium leprae

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23
Q

Why should you not Gram stain an acid-fast bacterium?

A

Acid-fast bacteria resist decolourisation by acid/ethanol after staining, so would falsely appear Gram-positive.

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24
Q

Name 2 possible stains which allow acid-fast bacteria to be visualised:

A

1) Ziehl-Neelson

2) Auramine fluorescence

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25
Q

How does acid-fast bacilli treated with the Ziehl-Neelson stain appear during microscopy?

A

The acid-fast bacilli appear bright red, against a blue background

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26
Q

What does a positive acid-fast bacterial smear indicate?

A

Infective patient contains acid-fast bacteria, ie tuberculosis/leprosy

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27
Q

Name 3 ways to grow bacteria:

A

1) Broth turbidity
2) In colonies (agar)
3) Biofilms

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28
Q

What type of bacterial growth is most representative of real life?

A

Biofilms

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29
Q

Why does a bacterial broth become turbid?

A

Due to number of bacteria present

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30
Q

What are the 3 general requirements for bacterial growth?

A

1) Specific energy source
2) Specific environment
3) Specific building block molecules

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31
Q

Why do humans provide a perfect atmosphere for (majority of) bacterial growth?

A
  • Anaerobic atmosphere
  • Provides energy source
  • Contain most building block molecules necessary for life
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32
Q

Name 2 types of gram positive cocci bacteria:

A

1) Staphylococcus

2) Streptococcus

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33
Q

Name a type of gram positive bacilli bacteria:

A

Clostridium

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34
Q

What type of shape is a Staphylococcus bacterium?

A

Cocci

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35
Q

Is a Streptococcus bacterium gram positive or negative?

A

Gram positive

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36
Q

Name a type of gram negative cocci bacterium:

A

Neisseria

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37
Q

Describe the shape of a Neisseria bacterium:

A

Cocci

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38
Q

Name 6 types of gram negative bacilli bacteria:

A

1) Escherichia
2) Salmonella
3) Helicobacter
4) Pseudomonas
5) Legionella
6) Bacteroides

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39
Q

Name 2 types of anaerobic bacteria:

A

1) Clostridium

2) Bacteroides

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40
Q

Describe the shape of a salmonella bacterium:

A

Bacilli

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41
Q

Is a Pseudomonas bacterium gram positive or negative?

A

Gram negative

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42
Q

Name a spore-forming bacterium:

Clue = it is also anaerobic

A

Clostridium

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43
Q

Define infection:

A

The establishment of an organism on or in a host associated with its multiplication and damage to, or dysfunction of the host specifically related to that organism or its products.

44
Q

In general, what causes infection?

A
  • Pathogenic microbes
  • Viruses
  • Prions
  • Bacteria
  • Archaea
  • Protozoa
  • Fungi
  • Helminths
45
Q

What are the extra bodies within cells which are sometimes produced during a viral infection?

A

Inclusion bodies which are inside the cytoplasm, where the viruses are replicating, and contain ribonuclear protein, ie Negri bodies of rabies virus

46
Q

What is used to view virus particles?

A

Electron microscopes

47
Q

What does ‘obligate intracellular parasite’ describe and mean?

A

Viruses, as they can only replicate within a host cell.

48
Q

Give the 3 main reasons why viruses are ‘obligate intracellular parasites’:

A

1) Viruses have no genes which encode proteins which function as the metabolic machinery for energy generation
2) Viruses have no genes that encode the proteins which function as the metabolic machinery for protein synthesis
3) Viruses may or may not contain the genes that encode enzymes involved in nucleic acid synthesis

49
Q

Can viruses contain both RNA and DNA?

A

No

50
Q

What is the evolutionary advantage of a virus with an RNA genome?

A

RNA is less stable than DNA, so mutates at a higher rate, allowing it to evolve rapidly through natural selection

51
Q

What kinds of small ions and polysaccharides do virus particles contain?

A

None

52
Q

Which out of enveloped and non-enveloped viruses contain lipids?

A

Enveloped viruses

53
Q

Do viruses contain lipids?

A

If they are enveloped they contain lipids, if they are naked viruses they do not contain lipids.

54
Q

What is the size of a virus particle (approximately)?

A

18-350nm

55
Q

What is the relationship between nm and mm?

A

1,000,000nm = 1mm

56
Q

Why are the growth curves of bacteria and viruses so different?

A

Bacteria divide exponentially, continuously, whereas viruses get into a cell, replicate, then large amount is released at one time (ie cell bursts)

57
Q

Why does segmented DNA/RNA sometimes give a virus an evolutionary advantage?

A

As re-assortment of the segments allows the virus to easily change and evolve through natural selection.

58
Q

Why are there 2 types of ssRNA?

A

Only one sense of RNA is the same sense as mRNA, so there are 2 types:

1) Positive sense = same sense as mRNA
2) Negative sense = complimentary sense to mRNA

59
Q

What are the 2 types of ssRNA?

A

1) Positive sense

2) Negative sense

60
Q

Which type of ssRNA is the same sense as mRNA?

A

Positive sense

61
Q

Which type of ssRNA is the complimentary sense to mRNA?

A

Negative sense

62
Q

Which type of ssRNA requires additional enzymes to those already present in a (host) cell, and why?

A

Negative sense ssRNA must be made into positive sense, so that the cell will accept it as mRNA, for transcription to occur

63
Q

What type of viruses must encode enzymes for their nucleic acids to be transcribed/translated by a host cell, and why?

A

Negative sense ssRNA, as cell cannot read this sense, must be converted to positive sense ssRNA
dsRNA, as cell cannot read this as mRNA, must be converted into positive sense ssRNA

64
Q

How are most viral infections specifically diagnosed?

A
  • genome directed nucleic acid amplification (PCR)

- specific immune response

65
Q

Some viruses convert their RNA into DNA for transcription and translation by the cell. What enzyme must they encode for this process to occur?

A

Reverse transcriptase

66
Q

Define nucleocapsid:

A

The capsid of a virus with the enclosed nucleic acid.

67
Q

How are the proteins produced put together to form virus particles?

A

They are programmed to self-assemble

68
Q

Define capsid:

A

The protein coat or shell of a virus particle, surrounding the nucleic acid or nucleoprotein core

69
Q

What is a capsid composed of?

A

Proteins which form individual subunits (capsomers), which self-assemble to form the capsid

70
Q

Define capsomere:

A

A subunit of the capsid, made of protein

71
Q

What are the 2 main functions of a capsid?

A

1) Protect the inner nucleic acid from the environment

2) Involved in attachment to host cells

72
Q

What part of a virus particle is involved in attachment to host cells?

A

The capsid

73
Q

What are the 2 basic capsid structural symmetries?

A

1) Icosahedral

2) Helical

74
Q

How may a virus leave the host cell without destroying it, and become an enveloped virus?

A
  • Produce proteins which self-insert into the membrane of the host cell
  • These recognise the virus particle, and allow it to bud through the membrane
75
Q

What is a bacteriophage?

A

A virus which parasitizes a bacterium by infecting it and reproducing inside it.

76
Q

What type of viruses are involved in the transfer of antibiotic resistance?

A

Bacteriophages

77
Q

What is required for a virus to successfully enter a host cell?

A

There must be correct receptor-ligand interaction:

  • correct receptor must be expressed by cell
  • correct ligand must be expressed by virus (on capsid of naked viruses, or envelope of enveloped viruses)
78
Q

What does HIV stand for?

A

Human Immunodeficiency Virus

79
Q

Why is it an important advantage for the virus to be enveloped in the host cell membrane?

A

The host cell membrane may contain host proteins which can be recognised by the hosts’ immune system, and ignored.

80
Q

What is required for a virus to successfully infect and replicate in a host cell?

A
  • Correct receptor-ligand interaction

- Cell must contain correct cellular machinery

81
Q

What is the host range of a virus?

A

The spectrum of host cells that the virus can successfully infect and replicate in

82
Q

What does it mean when a viral infection is ‘productive’?

A

The virus can successfully replicate inside the host cell.

83
Q

What does the host range of a virus depend on?

A
  • Correct receptor-ligand interaction between the virus and host cell
  • Cell must have correct cellular machinery to allow replication of virus genome
84
Q

What is the most commonly used classification scheme for viruses, and what is it based on?

A

Baltimore scheme, which compares the viral genome to the mRNA used for translation of the viral genome

85
Q

What type of classification of viruses is used in medical virology?

A
  • Nucleic acid

- Envelope

86
Q

What type of viruses are more susceptible to disinfectants?

A

Enveloped viruses

87
Q

Why are enveloped viruses more susceptible to disinfectants, than non-enveloped viruses?

A

The envelope of a virus is made up of lipids, which are easily dissolved via disinfectants, leaving nucleic core vulnerable.

88
Q

Define cytopathic effect:

A

Visible effects on the host cell caused by viral replication

89
Q

What are the 5 main cytopathic effects:

A

1) Death of the cell
2) Inclusion bodies
3) Syncytia formation
4) Chromosomal damage
5) Inhibition of host cell protein/RNA/DNA synthesis

90
Q

Why may viral infection cause the inhibition of the host cell protein/RNA/DNA synthesis?

A

Virus may divert the host cell function, to concentrate on producing more viral particles

91
Q

What type of viruses can cause cancer directly?

A

Retroviruses - positive sense ssRNA virus

92
Q

How can retroviruses directly cause cancer in a host?

A
  • Integrates all/part of genome into host cell DNA

- Bring in or turn on oncogenes, causing cell to proliferate uncontrollably

93
Q

Why is it extremely hard to treat cancer caused by viruses?

A

The cancer is caused by the integration of the viral genome into the host cell DNA, so drugs which suppress viral replication will have no effect

94
Q

Some viruses have the correct ligand for interaction with many receptors expressed by one cell. How does this benefit the virus?

A

If one receptor develops a mutation, there are still many other possible ways for the virus to gain entry to the cell

95
Q

How can a virus with a small amount of genes encode a large amount of proteins?

A

Multiple reading frames and alternative splicing

96
Q

Why do immunocompromised patients show different symptoms (to previously healthy patients) during viral infection?

A

Most of the symptoms of viral infection is produced by the immune system, triggered by the virus.

97
Q

When dealing with deadly viral infections, why do the responsibilities of a doctor change?

A

As if the correct processes are not followed, it could cause an epidemic. The doctors responsibility is not just for the individual patient, but the whole community.

98
Q

How does Ebola affect the host immune system?

A
  • Reduces the effective immune response

- Enhances the unproductive response (inflammation)

99
Q

Define incubation period:

A

The period between exposure to an infection and the appearance of the first symptoms

100
Q

Why are a lot of viral infections asymptomatic?

A

It allows more virus particles to be made which can then be transmitted to new hosts.

101
Q

Define latent infection:

A

An asymptomatic infection capable of producing symptoms under particular circumstances or if activated

102
Q

How are new virus particles released from the host cell?

A
  • Cell lysis

- Budding of enveloped viruses

103
Q

What are the 4 words used to describe the duration of an infection?

A

1) Acute
2) Subacute
3) Chronic
4) Latent

104
Q

Give 3 possible routes of environmental transfer of an infection:

A

1) Respiratory
2) Faecal-oral contamination
3) Transcutaneous (inoculation)

105
Q

What is the main difference between viral and bacterial infections, in terms of spreading through the host?

A

Viruses can spread via multiple pathways, ie through nerves to nervous system, via blood to organs etc. Bacteria are more localised.

106
Q

What is cell-mediated immunity?

A

An immune response which does not use antibodies, but instead activates phagocytes, antigen-specific cytotoxic T-lymphocytes, and the release of various cytokines in response to an antigen

107
Q

What type of immunity primarily stops viral infection?

A

Cell-mediated immunity

ESA1 (22 decks)

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