Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Microbiology > Lab 28: Bacteria of the skin > Flashcards

Lab 28: Bacteria of the skin Flashcards

You may prefer our related Brainscape-certified flashcards:
Biology 101 flashcards
1
Q

what organ is the skin?

A

the largest organ of the body

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

what are the skin’s functions?

A

Physical barrier to pathogens
Senses environment
Regulates temperature
Restricts loss of fluids

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

what line of defense is the skin?

A

first line of defense

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

what are the 3 layers of the skin?

A
  1. Epidermis (most surface level)
  2. Dermis
  3. Hypdermis (deepest layer)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

describe the epidermis

A

-Outermost, avascular layer (no blood vessels).
-Made of 4-5 layers
-Stratum basale: deepest layer
-Stratum corneum: topmost layer

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

what does the stratum basale contain?

A

Bottom most/deepest layer:
-1 cell thick
-Made of basal cells, which are alive
-Cells undergo division, new cells pushed out towards the top layers

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

what does the stratum corneum contain?

A

Topmost/surface layer:
-10-35 cells thick
-Made of dead cells called keratinocytes
-Constantly flake off carrying away pathogens (flushing action)
-Basal cells differentiate into keratinocytes as they move up, they make keratin, waterproofing lipids, change shape from cuboidal to flat, lose organelles and die

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

what does the dermis layer contain?

A

-connective tissue layer
-contains nerves, glands, blood vessels, lymphatic vessels, adipocytes, and hair follicles
-has pressure, temperature, and pain receptors
-provides nourishment to the epidermis

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

what are three ways that the dermis helps to fight off pathogens?

A
  1. Sweat glands: produce salty sweat that inhibits microbes
  2. Sebaceous glands: produce sebum, an oily secretion that keeps hair and skin soft, flexible, and water-repellant.
  3. Normal microbiota: break down (aka metabolize) lipids into toxic fatty acids that inhibit microbes and are toxic to pathogens.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

what is the hypodermis?

A

-Subcutaneous tissue
-Contains adipose tissue and blood vessels

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

what are common skin microbiota/common skin bacteria:

A
  1. Propionibacterium (G +)
  2. Staphylococcus (G +)
    - Including S. epidermidis and S. aureus
  3. Corynebacteriaceae family (G +)
  4. Proteobacteria phylum (G -)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

what is Staphylococcus epidermis part of?

A

The normal microbiota

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

what type of clusters are found in Staphylococcus epidermis?

A

Gram positive cocci in clusters

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

can S. epidermidis cause infection? is it virulent?

A

It can cause infection if they enter a wound or are displaced - it is NOT very virulent.
However, it can cause severe infections only in immunocompromised.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

what is Staphylococcus aureus a part of?

A

Transient microbiota of the skin, and nasal passage

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

what type of clusters are S. aureus found in?

A

Gram positive cocci in clusters

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

how many people are asymptomatic carriers of S. aureus?

A

2-30% of people are asymptomatic carriers. You can be a carrier and still pass it on to other people

18
Q

can S. aureus cause severe infections?

A

Yes, it can cause severe infections like pneumonia, staphylococcal scalded skin syndrome, staphylococcal food intoxication, staphylococcal TSS, etc.

19
Q

how can we identify S. aureus in the lab?

A

Using the MSA medium: high salt (7.5%) NaCl allows the growth of halotolerant skin bacteria.

20
Q

how does S. aureus show up on the MSA plate?

A

S. aureus ferments mannitol and turns yellow on MSA plates; S. epidermidis stays pink.
If we see yellow colonies, we know we are a carrier of S. aureus.

21
Q

We have to confirm that S. aureus is actually present since we cannot only rely on the MSA test. What other tests can we use to determine if S. aureus is present?

A

It is:
Gram +
Catalase + (H2O2)
Coagulase +

22
Q

what happens when you have a coagulase + test?

A

-During normal clotting, signals from damaged tissues activate plasma protein prothrombin to form thrombin.
-Thrombin converts plasma protein fibrinogen into fibrin - which is an insoluble protein that forms a mesh that traps blood cells to form a clot.
-Coagulase activates thrombin causing S. aureus to coat itself with fibrin mesh - which helps it to hide/evade the immune system and attached to the cells to cause infection.

23
Q

what do we incubate for a coagulase test?

A

bacteria + rabbit plasma incubated at 37 degrees C for 4 hours

24
Q

how do you know if a coagulase test is + for S. aureus?

A

Coagulations

25
Q

if there is no coagulation, what do we conclude?

A

CoNS (coagulase-negative staphylococci)

26
Q

how does S. aureus hide from the immune system?

A

it covers itself with a fibrin mesh/clot formed by coagulase

27
Q

what kind of infection can S. aureus cause?

A

Hair follicle infections - S. aureus enters the skin through hair follicles to the dermis and causes inflammation, etc.

28
Q

what is folliculitis?

A

First stage of the infection:
Inflammation of hair follicles.
Small red bumps or pimples form, it is self-clearing.

29
Q

what is Fununcle (boil)?

A

Second stage of the infection:
Infection spreads to adjacent tissue.
Abscess formation (redness, swelling, pain).

30
Q

what is the carbuncle?

A

Third stage of the infection,
Infection spreads to a larger area.
Abscess + fever.
May require minor surgery to drain pus
Antibiotics given

31
Q

what is the prevention of hair follicle infections?

A

hand washing

32
Q

why is S. aureus so good at causing infections?

A

Because of its virulence factors

33
Q

what are the 6 virulence factors of S. aureus?

A
  1. Capsule
  2. Clumping factor
  3. Protein A
  4. Coagulase
  5. Enzymes
  6. Toxins
34
Q

what does the capsule do for the virulence factor?

A

prevents phagocytosis (basically prevents binding of sentinel cells)

35
Q

what does the clumping factor do for the virulence factor?

A

allows cells to crosslink and form a big clump that is hard to phagocytose; allows attachment of cells to damaged host cells and medical devices coated with fibrinogen

36
Q

what does Protein A do for S. aureus virulence factors?

A

prevents opsonization and ADCC

37
Q

what does coagulase do for S. aureus virulence factors?

A

S. aureus forms a clot of fibrin mesh around itself to help evade the immune system

38
Q

what do enzymes do for S. aureus virulence factors?

A

break down host proteins, lipids, etc.

39
Q

what do toxins do for S. aureus virulence factors?

A

kills host cells including leukocytes (WBCs)

40
Q

add results here

A

Microbiology (53 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions