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Pathogenic Microbiology > Lecture 9: Staphylococcal > Flashcards

Lecture 9: Staphylococcal Flashcards

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Biology 101 flashcards
1
Q

What are the 2 divisions of Staphylococcus?

A

Coagulase + are usually S. aureus and pathogenic

Coagulase - are organisms like S. epidermidis are less invasive

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2
Q

What are the General Characteristics of the Staphylococci?

A
  1. common inhabitant of the skin and mucous membranes
  2. Spherical cells arranged in irregular clusters
  3. Gram-positive
  4. Lack of spores and flagella
  5. extracellular pathogen
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3
Q

What are the characteristics of staphylococcus aureus?

A
  1. Grows in large round colonies-grape like
  2. Golden yellow colonies on blood agar plate
  3. Facultative anaerobe
  4. Withstands high salt, extremes in pH, and high temperatures
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4
Q

What are the 2 divisions of disease produced by staphylococcus aureus?

A
  1. Infections

2. Intoxication

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5
Q

What are the stages of the mechanism of pathogenesis of staphylococcal infection?

A
  1. bacteria gains access to damage skin, mucosa or tissue site
  2. colonized by adhering to cells or extracellular matrix
  3. evade the host defense mechanism and multiple
  4. causes damage
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6
Q

What are the bacteria portals in the local infection affecting skin and soft tissue of staphylococcal disease?

A
  • hair follicle

- break in the skin (needle-stick or a surgical wound)

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7
Q

What are the 4 types of system infection of staphylococcus?

A
  1. osteomyelitis
  2. bacteremia
  3. endocarditis
  4. pneumonia and empyema
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8
Q

What is osteomyelitis?

A

S. aureus invasion of the bone (through wound or bacteremia), inflammation of bone marrow and surrounding bone

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9
Q

What is bacteremia?

A

bacteria in the blood. Primary origin is bacteria from another infected site or medical devices

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10
Q

What is endocarditis?

A

attacks the lining of the heart (including its valves). Non-specific flu-like symptoms but conditions quickly worsens as the amount of blood pumped from the heart drops.
50% mortality rate.

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11
Q

What is the difference between pneumonia and empyema?

A

Pneumonia - inflammation of lungs, fluid fills within alveoli and bronchioles.
Empyema - collection of pus in the space between the lung and the inner surface of the chest wall.

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12
Q

What are the 3 types of intoxication of staphylococcus?

A
  1. food
  2. skin - staphylococcal scaled skin
  3. toxic shock syndrome
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13
Q

What is food intoxication?

A

ingestion of heat-stable enterotoxins (not the bacteria itself); gastrointestinal distress

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14
Q

What is scalded skin syndrome?

A

toxin induces bright red flush, blisters, then pealing of the epidermis

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15
Q

What is toxic shock syndrome?

A

toxemia leading to shock and organ failure

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16
Q

What are the symptoms of toxic shock syndrome (TSS)?

A 
8-12 h post infection
Fever
Susceptibility to Endotoxins
Hypotension
Diarrhea
Multiple Organ System Failure
Erythroderma (rash)
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17
Q

What is the structural component of protein A?

A

Type I membrane protein which binds immunoglobulin (IgG) molecules on their heavy chain within the Fc region to render them ineffective

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18
Q

What are some traits of Coagulase?

A

Can be bound to the outer surface of the bacteria or cell-free
Highly correlated with virulence - most (but not all) virulent strains are coagulase positive

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19
Q

What are the extracellular factors of s. aureus?

A
  1. Enzymes

2. toxins

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20
Q

What does Hyaluronidase do?

A
  1. Breaks down hyaluronic acid, major component of the matrix between cells (digests connective tissue)
  2. Enables bacteria to spread between cells throughout the body
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21
Q

What does Staphylokinase do?

A

Dissolves fibrin threads in blood clots, allowing S. aureus to free itself from clots
Helps bacterial spread to new locations

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22
Q

What are the functions of lipases S. aures?

A

They hydrolyze lipids
they may help the bacteria survive in sebaceous glands in the skin (enhances colonization)
may aid in development of skin infections and subcutaneous infections

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23
Q

What do hemolysis do?

A

Hemolysins (α, β, γ, δ) – lyse red blood cells

24
Q

What is delta toxin?

A

a very small peptide toxin produced by most strains of S. aureus and S. epidermidis that lyse red blood cells

25
Q

What do B-toxin do?

A

sphingomyelinase which damages membranes rich in this lipid

The majority of human isolates of S. aureus do not express ß-toxin

26
Q

What do Leukocidin do?

A

lyse neutrophils and macrophages

27
Q

What are the causes of community-acquired MRSA?

A 
skin/soft tissue infections (77%)
wound infections (10%)
urinary tract infections (3%)
bacteremia (3%)
lung infections (2%)
Other infections: necrotizing pneumonia, severe sepsis, necrotizing fasciitis,  endocarditis, etc.
28
Q

Where are the common outbreaks of community-MRSA?

A

Prisons
Child day-care centers
Sports teams
Military recruits

29
Q

Why has vaccine efforts been vain for s. aureus?

A

S. aureus expresses a large array of virulence factors such that a vaccine against any one may not prove effective.

30
Q

What is infection?

A

The disease is caused by the bacteria themselves

31
Q

What is intoxication?

A

The disease is caused by bacterial exotoxins, which are produced either in the infected host or performed in vitro

32
Q

what are some of the pre dispositions to infection?

A
  1. poor hygiene
  2. poor nutrition
  3. tissue injury
  4. preexisting primary infection
  5. diabetes
  6. immunodeficiency
33
Q

what are traits of cell associated polymers?

A
  1. cell wall polysaccharide
  2. teichoic acid (in peptidoglycan layer of gram positive)
  3. capsular polysaccharide
34
Q

how does Staph protect itself from phagocytosis?

A
  1. protein A
  2. bound coagulase
  3. capsule
35
Q

What does coagulase capsule do?

A
  1. inhibits chemotaxis of and endocytosis by leukocytes and aids in attachment
  2. Converts fibrinogen into insoluble fibrin which causes clotting
36
Q

What are the enzymes for virulence of staphylococcus?

A
  1. free coagulase
  2. catalase
  3. lipase
  4. hyaluronidase
  5. DNAase
  6. thermonuclease
  7. staphylokinase
  8. phosphatase
37
Q

What do DNase do?

A

marker for virulence, digests DNA

38
Q

What does penicillinase do?

A

inactivates penicillin

39
Q

What do enterotoxins do?

A
  1. they stimulate muscle contractions, nausea, and intense vomiting associated with food poisoning.
  2. when expressed systemically, can cause toxic shock syndrome
40
Q

How does alpha hemolysin work?

A
  1. binds to the membranes of susceptible cells in a monomeric form
  2. subunits then oligmerize to form heptameric rings with central pore through which cellular contents leak
  3. Platelets and monocytes are particularly sensitive to alpha toxin
41
Q

What do exfoliative toxins do?

A

separates the epidermis from the dermis

42
Q

What do Toxic shock syndrome toxin (TSST) do?

A

induces fever, vomiting, shock, systemic organ damage

43
Q

which toxins have superantigen activity?

A
  1. enterotoxins, they stimulate T cells non specifically without normal anitgenic recognition
  2. toxic shock syndrome toxin
44
Q

what are the 6 antigenic types of enterotoxin?

A

SE-A through SE-G

45
Q

what is special about enterotoxins B and C?

A

cause 50% of non menstrual cases of TSS

46
Q

what are the properties skin has to prevent S. aureus colonization?

A
  1. low temperature
  2. low pH
  3. skin commensals
  4. antimicrobial peptides
47
Q

what do keratinocytes do?

A

they produce keratin and express recognition receptors such as TLR2 and NOD2

48
Q

what does TLR2 do?

A

recognizes S.aureus lipopeptides and lipotechoic acid

49
Q

what does NOD2 do?

A

recognizes S. aureus peptidoglycan breakdown product muramyl-peptide

50
Q

what does TLR2 and NOD2 signaling lead to?

A

activation of NF-kB and other transcription factors that induce transcription of pro-inflammatory mediators

51
Q

what does S. aureus infection of skin result in?

A
  1. production of IL-1a, IL-1b, and IL-17
  2. induce keratinocyte production of anitmicrobial peptides
  3. granulopoiesis factors that promote neutrophil recruitment
52
Q

what is Mecin/PBP2a?

A

a penicillin binding protein that is intrinsically insensitive to methicillin and all beta lactams that have been developed

53
Q

What is Protein A?

A

an abundant surface protein that is able to interact with the Fc portion of immunoglobulin, suppressing the adaptive immune response by limiting B cell antibody production.

54
Q

What do Coagulases do?

A

Converts fibrinogen into insoluble fibrin which causes clotting

55
Q

What doe B-lactamase influence?

A

treatment options

56
Q

What species of Staphylococcus produces delta toxins?

A

S. epidermidis.

Pathogenic Microbiology (12 decks)

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