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MSE-2019 Medical Microbiology > Lecture 4 Oxygen and Drugs > Flashcards

Lecture 4 Oxygen and Drugs Flashcards

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Biology 101 flashcards USMLE® Step 1 flashcards
1
Q

What does obligate aerobe mean?

A

Oxygen is essential

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2
Q

What is the molecular formula for normal atmospheric oxygen?

A

O2

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3
Q

Why are highly reactive forms of oxygen toxic?

A

They are oxidising (is able to steal electrons from other compounds)

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4
Q

What would happen if I gave oxygen to an obligate anaerobe?

A

It would die lmao

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5
Q

What does an oxidising agent do?

A

Steals electrons from other compounds.
Causes the electron depleted compound to steal electrons from another compound.
So on and so forth
Creating a chain of vigorous oxidation

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6
Q

ToD: Oxidation dmg is reversible

A

False.
Oxidation dmg is irreversible to cells.

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7
Q

What compounds are oxidised causing irreversible dmg?

A

Proteins
Lipids

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8
Q

How many forms of oxygen are there?

A

Four

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9
Q

What does Singlet Oxygen look?

A

O2

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10
Q

What happens to the electrons found within Singlet Oxygen?

A

Aerobic metabolism causes the electrons to be boosted to a higher energy state

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11
Q

What cells use Singlet Oxygen?

A

Phagocytic cells use singlet oxygen to oxidise pathogen

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12
Q

How reactive is Singlet Oxygen?

A

Very reactive oxidising agent

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13
Q

What is the molecular formula for Superoxide Radical?

A

O2-

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14
Q

How are Superoxide Radicals formed?

A

O2- forms during the incomplete reduction of O2 during electron transport in aerobes
&
the metabolism by anaerobes in the presence of oxygen

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15
Q

ToD: Only Anaerobes create Superoxide Radicals

A

False.
Both aerobes and anaerobes can create superoxide radicals

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16
Q

What do aerobic organisms create to detoxify themselves of superoxide radicals?

A

Superoxide dismutase

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17
Q

What do anaerobic organisms create to detoxify themselves of superoxide radicals?

A

Nothing

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18
Q

What is created when you combine two superoxide radicals and two protons?

A

Hydrogen peroxide (H2O2) + Oxygen

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19
Q

What is the molecular formula for Peroxide Anion?

A

O2 2-

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20
Q

What do aerobes have to detoxify themselves of peroxide anion?

A

Catalase or Peroxidase

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21
Q

How are peroxide anions created?

A

They are produced as a biproduct of reactions catalysed by superoxide dismutase

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22
Q

What can you use peroxide anions to make?

A

Hydrogen peroxide

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23
Q

What can hydrogen peroxide be used for?

A

It’s an antimicrobial agent

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24
Q

If there are more metal ions in the body, which form of oxygen is created more?

A

Superoxide radical

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25
Q

Out of the 4 forms of oxygen, which is the most reactive?

A

Hydroxyl radical

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26
Q

What is the molecular form of hydroxyl radical?

A

OH

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27
Q

How are hydroxyl radicals formed?

A

From ionising radiation and from the incomplete reduction of hydrogen peroxide

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28
Q

What enzymes get rid of the hydroxyl radicals?

A

Catalase and peroxidase

29
Q

ToD: Aerobes produce catalase and peroxidase to get rid of hydroxyl radicals?

A

True. The build up of hydroxyl radicals can damage proteins, lipids and DNA.

30
Q

What vitamins are considered antioxidants?

A

Vitamin C
Vitamin E

31
Q

What makes vitamins antioxidants?

A

Able to provide electrons that can reduce the toxic forms of oxygen

32
Q

What are facultative anaerobes?

A

Can live in various oxygen concentrations

33
Q

What are the two processes that help facultative anaerobes survive?

A

Fermentation
Anaerobic respiration (least efficient due to lack of oxygen)

34
Q

What bacteria is an example of a facultative anaerobe?

A

E.coli

35
Q

What bacteria is an example of aerotolerant anaerobes?

A

Lactobacilli

36
Q

What kind of metabolism does aerotolerant anaerobes use?

A

Anaerobic metabolism

37
Q

At what percentage of atmospheric oxygen are microaerophiles damaged by?

A

21%

38
Q

What bacteria is an example of an microaerophile?

A

Helicobacter pylori- ulcer causing pathogen in the stomach

39
Q

What percent of IDU hospital admissions are due to infections?

A

40%

40
Q

What are the three different types of injection?

A

Intravenous
Intra-muscular
Subcutaneous

41
Q

What can cause local abscess formation?

A

Minor bacterial infections

42
Q

What can cause severe illness if it contaminates injected material or paraphernalia?

A

Clostridial spores

43
Q

Of IDU hospital admission, what percentage results in death?

A

20%

44
Q

Where can you find Clostridia?

A

Widely distributed in soil and gut

45
Q

ToD: Clostridia is gram positive?

A

True

46
Q

What are the characteristics of Clostridia?

A

Gram Positive
Anaerobic
Spore-forming rods
Resistant to environmental conditions
Can exist as exo-spores
May release powerful exotoxins

47
Q

What is required for clostridia spores to germinate?

A

When introduced to an oxygen-reduced environment

48
Q

What can injecting substances into the muscle tissue do?

A

Increases the risk of infection via clostridium spores

49
Q

What can be observed on the soft tissue if someone is infected by clostridium spores?

A

Abscess
Cellulitis
Fasciitis
Myositis

50
Q

What are severe localised symptoms if someone is infected by clostridium spores?

A

Extensive swelling
Pain
Oedema
Erythema with blackening/blistering at centre
Extensive necrosis
Necrotising fasciitis

51
Q

Hypothetically if you took drugs and the veins on your arms were too dmged to take more drugs what would you do?

A

Other areas of the body are free real state
e.g Groin area, behind the knees, neck

52
Q

Where can you find C.novyi Type A?

A

Widely distributed in soil

53
Q

What can be seen on the blood agar if C.novyi Type A is being grown?

A

After 24H: Small, flat, rough or rhizoidal, translucent haemolytic colonies with a spreading edge
After 48-72H: Colonies often coalesce to give fine spreading growth

54
Q

Why shouldn’t colonies of C.novyi Type A be exposed to air?

A

Toxic because the colonies haven’t begun sporulation

55
Q

4 Characteristics of C.novyi Type A

A

Unreactive in commercial anaerobe identification kits (API Anaerobe)
Gram-variable
Rod shaped
Some sub-terminal spores

56
Q

Where can you find C.perfringens?

A

Post-mortem contaminant
Basically dead bodies and necrophiles

57
Q

What are the characteristics of C.perfringens?

A

Gram-variable
Rod shaped
No spores

58
Q

What should you see if C.perfringens is growing on blood agar?

A

24H: Large discrete colonies. Flat and rough-edged or smooth and domed.
Non-haemolytic or with a narrow zone of complete haemolysis inside a larger zone of partial haemolysis

59
Q

What are the characteristics of C.septicum?

A

Grows rapidly
Haemolytic
Gram variable
Rods
Numerous sub-terminal spores

60
Q

Where can you most commonly find C.septicum?

A

Can be found from blood cultures of patients with malignancies of the colon

61
Q

What diseases can C.botulinum cause?

A

Food-borne illnesses
Cases of wound botulism

62
Q

What are the characteristics of C.botulinum?

A

Haemolysis is variable
Gram variable bacilli
Profuse sub-terminal and free spores

63
Q

What is observable on the blood agar if C.botulinum is being grown?

A

Proteolytic types A, B and F will initially produce discrete rhizoidal colonies that spread and coalesce

64
Q

What is observable on the blood agar if C.tetani is being grown?

A

May produce fine swarming growth

65
Q

What can be seen on the Gram stain of C.tetani?

A

When left overnight, you will be able see over-decolourised long bacilli without spores

66
Q

What three antibiotics can be given to treat C.histolyticum

A

Penicillin
Metronidazole
Clindamycin

67
Q

What is the treatment for patients presenting with compartment syndrome?

A

Urgent decompression
Excision of surrounding oedematous tissues

68
Q

What are the three early surgical interventions for C.histolyticum?

A

Exploration
Drainage
Extensive debridement

MSE-2019 Medical Microbiology (6 decks)

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