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Micro Lab Practical 4 > 28. Bacteria Of The Skin > Flashcards

28. Bacteria Of The Skin Flashcards

1
Q

What are the 3 layers of the skin?

A

1) epidermis
2) dermis
3) hypodermis

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2
Q

What are the characteristics of the epidermis?

A
  • most superficial layer
  • avascular (lacks blood vessels)
  • varies in composition in different parts of the body
    • 10-35 cells in thickness
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3
Q

What are the 2 layers of the epidermis explained in the lab?

A
  • stratum basale (deepest part of epidermis)
    • 1 cell thick
    • contain basal cells that are attached to the basement membrane
  • stratum Corneum (most superficial)
    • 10-35 cells thick
    • contain keratinocytes (inactive and lack organelles)
    • constantly slough from the skin
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4
Q

As basal cells are pushed away from the stratum basalem they undergo a differentiation process. What happens here?

A
  • synthesis of keratin and secretions of waterproofing lipids
  • cell membranes get thicker and organelles are broken down.
    • they also change shape going from cuiboidal to squamous
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5
Q

What are the characteristics of the dermis?

A
  • contains blood vessels, fibroblasts, collagen fibers, adipocytes, hair follicles, sweat glands
  • contains pressure, temperature, and pain receptors
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6
Q

What are the characteristics of the hypodermics/ subcutaneous layer?

A
  • deepest layer of the skin

- contains mostly adipose tissue (fat)

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7
Q

What are the 4 common groups of skin bacteria?

A

1) Propionibacterium genus (gram +)
2) Staphylococci (gram +)
3) Corynebacterium (gram +)
4) proteobacteria (gram -)

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8
Q

2 common skin bacteria (characteristics)

A

Staphylococcus epidermidis

- normal microbiota
- Gram + cocci, clustered growth
- not highly virulent
- severe S. Epi infections limted to immunocompromised persons

Staphylococcus aureus

- Gram + coccus
- colonizes the skin
- classified as a primary pathogen
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9
Q

All members of the Staaphylococcus genus is able to grow on what kind of media? What kind of medium can be used?

A
  • high salt media
    • MSA: contains height concentration of salt (7.5%)

-high salt media suppresses the growth of many organisms, but not S. Epi and S. Aureus

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10
Q

How is S. Epidermidis and S.Aureus differentiated using MSA?

A
  • MSA contains mannitol and a pH indicator
    • S. Aureus ferments mannitol to acidic products (lactic acid) > grows yellow colonies
    • S. Epidermidis does not ferment mannitol > grows pink or red colonies
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11
Q

S. Aureus cells secrete what kind of protein? What is its function

A
  • coagulase
    • activates prothrombin, turning it into thrombin
  • Thrombin allows S. Aureus cells growing inside people to coat themselves with fibrin mesh
    • contributes to the virulence of S. Aureus (avoids detection, attach, trigger inappropriate blood clots near sites of infection
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12
Q

Why are the cells of the stratum corneum not adequate hosts for viruses?

A
  • cells are dead

- not able to do protein synthesis or nucleic acid replication

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13
Q

Describe the mechanical and physiological antimicrobial defenses found on and in the skin

A

1) many layers; anchoring proteins
2) skin is thick

3) outer layers (stratum corneum)
- dead cells
- no viral replication
- keratin protein (hard to digest)

4)perspiration >salts > inhibit some microbes

5) sebum: fungistatic
- antimicrobial peptides

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14
Q

Where on and in the skin are the normal microflora found?

A
  • skin surface
  • hair follicle
  • sebaceous gland
  • sweat gland
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15
Q

Which integumentary system locations have high density of microflora?

A
  • intertriginous skin ( any skin that comes in contact with any other skin)
    • more moist
    • accumulation of dead skin cells

-scalp

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16
Q

Which integumentary system locations have low density of microflora?

A
  • dry skin
  • nails
  • outer ear
17
Q

How do normal microflora of skin help protect us against skin infections

A
  • acids decrease pH
    • suppresses pathogens
  • competitive exclusion
    • microbial antagonism
    • microflora consuming nutrients, so pathogen cannot consume them
    • secrete bacteriocins (short proteins/peptides> attack other bacteria)
18
Q

What is the % of people that have S. Aureus…
Nose
Throats

Healthcare workers

A

Nose and throat: 10% of people in the population

healthcare workers: 30%>

19
Q

Are all strains of S. Aureus equally pathogenic?

A
  • No
    • vary with respect to their ability to cause disease
    • some are weak and some have virulence factors
    • production of certain toxins
    • vary of resistance to antibiotics
20
Q

What is the function of the enzyme coagulase ?

How would you detect the presence of this enzyme in the lab?

A

-allows the bacteria to cause inappropriate blood clots

  • Coagulase test
    • you supply clotting factors; plasma that contains fibrinogen
    • Positive test:tube coagulates
21
Q

Which species test positive and negative for coagulase?

A

+: S. Aureus

-:S. Epidermidis, S. Saprophyticus. (CoNS)

22
Q

Describe what a furuncle is

A

-Staphylococcus infects hair follicle

23
Q

Describe a non bulbous impetigo

A

Infection of the skin frequently around the mouth and nose but can occur at any broken skin

-non bullous:crusty yellow fluid from pustules; may be caused by strep

24
Q

Describe bollous impetigo

A

-S. Aureus releases proteases (“exfoliating toxins”) that digest anchoring proteins in the epidermis;Bullous result

25
Q

Describe what a ecthyma is

A
  • deep impetigo, causing skin lesions

- may be caused by Streptococcus

26
Q

What is the general definition of pneumonia

A
  • when an organism infects the alveoli of the lungs
27
Q

Virulence factors of S. Aureus

A
  • exfoliating toxin
  • coagulase
  • leukocidin
    • toxin that kills WBC/neutrophils
  • Hyalauraonidase
    • digests ECM around epithelial cells
    • spreads inside the body
  • Protein A
    • Binds to Fc region of antibody
  • Staphylokinase
    • activates plasmin (control blood clotting)

-enterotoxin

-toxic shock syndrome toxin
-

28
Q

S. Aureus food intoxication

A
29
Q

Which properties of the Rely tampon contributed to the increase in the number of cases of toxic shock in the late 1970s?

A
  • it changed the environment of the vagina that it promoted the growth of S. Aureus
    • Rely were 20x more absorbent that they were able to keep them in for almost a day
    • carboxymethylcellulose promoted the growth of S. Aureus
30
Q

What are superantigens?

A
  • proteins/toxins
    • overstimulate immune system
      • cross link T cell receptors on CD4 T-cells to MHC2 protein
      • cytokine storm (too many cytokines) > toxic shock syndrome
31
Q

Name 3 superantigens. Which 2 cause toxic shock or similar syndromes?

A

Toxic shock syndrome toxins ‘TSST-1’ (S. Aureus) > toxic shock syndrome

Enterotoxin ( S. Aureus) > NVD cramps

Streptococcus pyogenes > Toxic shock syndrome

32
Q

What are antigens

A
  • molecules/structures that lymphocytes recognize as foreign

- stimulate the adaptive immune system

33
Q

What are the symptoms of toxic shock syndrome

A
  • decrease in blood pressure
  • pulmonary edema
  • DIC; microscopic blood clots throughout body uses up clotting factors (coagulopathy)

Micro Lab Practical 4 (7 decks)

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