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Microbiology > staphylococci > Flashcards

staphylococci Flashcards

1
Q

Gram positive Cocci has what shape

A

spherical

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2
Q

Gram positive Cocci have an absence of

A

endospores

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3
Q

Catalase positive genera

A

staphylococcus

micrococcus

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4
Q

Catalase negative genera

A

streptococcus

enterococcus

Anaerobic gram positive cocci

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5
Q

properties of staphylococcus

A

nonmotile (cant move itself)

Facultatively anaerobic (can switch to not using oxygen)

halotolerant = living in conditions of high salinity

Temperature range 18-40*c

simple media

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6
Q

where is staphylococcus found

A

skin and mucous membranes

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7
Q

What is the most virulent staphylococcus

A

s. aureus
- only species to produce enzyme coagulase
- can survive well in the enviroment and is easily spread from person to person

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8
Q

what is staphyloccus golden

A

produces carotenoid pigments

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9
Q

staph aureus: Virulence factors

A

Structural components

toxins

enzymes

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10
Q

Staph aureus: structural components

A

capsule
- loose fitting slime layer

Seen occasionally in vitro

inhibits:

  • Chemotaxis
  • phagocytosis

facilitates adherence

peptidoglycan layer

Teichoic acids aid attachment to host via fibronectin receptors

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11
Q

Staph aureus: Structural components:

Protein A ….

A

Coats surface

binds Fc receptors of IgG1,2 and 4

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12
Q

Staph aureus: Structural components:

extracellular protein A…

A

Binds antibodies

forms immune complexes

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13
Q

Staph aureus: Structural components:

Bound coagulase - clumping factors

A

Binds fibrinogen and converts to fibrin

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14
Q

Staph aureus: Structural components:

Cytoplasmic membrane:

A

Transport and anchorage

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15
Q

Staphylococcal toxins

A

Cytolytic
- membrane damaging toxins

Alpha, beta, delta, gamma and leukocidin

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16
Q

what cells are staphylococcal toxic too

A

leukocytes

erythrocytes

macrophages

platelets

fibroblasts

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17
Q

Staphylococcal exfoliative toxins

A

names = exfoliatin, epidermolytic toxin

causes = scales skin syndrome

characterised by exfoliative dermatitis

two distinct forms, A and B , either can produce disease

seen mostly in young children

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18
Q

toxic shock syndrome toxin ! (TSSTS1)

A
  • Fever
  • Hypotension
  • Rash
  • Followed by desquamation
  • Multi organ system involvement
  • Toxin secreted during growth
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19
Q

how many serologically distinct exotoxins

A

5

named from A to E

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20
Q

Staphylococcal Enterotoxins are resistant too

A

hydrolysis by gastric and jejunal enzymes.

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21
Q

Staphylococcal Enterotoxins has a percentage of strains that produce what

A

30-50% produce enterotoxin

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22
Q

Enterotoxin A mostly associated with

A

… disease

23
Q

Staphylococcal Enterotoxins are strong induces of

A

cytokine response

24
Q

Staphylococcal Enterotoxins has two forms what are these forms and their explanation

A

Bound directly converts fibrinogen to fibrin and causes visible clumping

cell free coagulase react s with a globulin plasma factor = staphylothrombin

this catalyses the conversion of fibrinogen to fibrin

25
Q

What does the staphylococcal enzymes do

Catalase

A

catalyses the conversion of toxic h202 to water and oxygen

26
Q

What does the staphylococcal enzymes do

  • Hyaluronidase
A
  • Breaks down hyaluronic acids in connective tissue

- Helps spread of bacteria through tissues

27
Q

What do all staphylococci all produce

A

Catalase

28
Q

what do 90% of Staphylococcal Enzymes

A

hyaluronidase

29
Q

what does fibrinolysin (staphylokinase):

A

dissolves fibrin clots

30
Q

Lipases:

A

To hydrolyse lipids and ensure survival in sebaceous areas

31
Q

All s,aureus and 30% CNS produce …

A

lipases

32
Q

Nucluease DNase is what stable

A

thermostable

33
Q

Penicillinase Beta-Lactamase production on

A

transmissible plasmids

34
Q

Epidemiology

A 
Ubiquitous 
Spread by:
-shedding
- Direct  contact 
- Fomites

Major source of hospital acquired infection

Lysozyme in tears etc forms natural barrier

35
Q

Staphylococall scaled syndrome symptoms

A

redness and inflammation around the mouth covers entire body in 2 days

Blisters contain clear fluid
- No wbc or bacteria

bu

36
Q

Staphylococall scaled syndrome symptoms

A

redness and inflammation around the mouth covers entire body in 2 days

Blisters contain clear fluid
- No wbc or bacteria

Bullous impetigo, localised from of sss

37
Q

Skin infections caused by staph aureus

A

Impetigo

folliculitis (styes)

Furuncles (Boils)

Carbuncles

Abscesses

Wound infections
- Skin colonising bacteria gain entry to wound

Cellulitis and infection of ulcers

38
Q

Toxic shock syndrome is associated with

A

local growth of S. aureus in wound or vagina and release of toxin into blood

increased risk associated with retained tampons

39
Q

Staphylococcal food poisoning

Most commonly infected foods are

contamination by,,,

toxic is ,,, stable

A

Intoxication rather than infection

Most commonly infected foods are:

  • processed meats
  • salted pork
  • Custard filled pastries
  • Potato Salad
  • Ice cream

Contamination by human bacteria

Toxin is heat stable

40
Q

Staphylococcal Food poisoning symptoms

symptoms

time

treatment

A

Rapid onset 4 hours

rapid course 24 hours

Severe:

  • vomiting
  • Diarrhoea
  • Abdo pain
  • Nausea

Treatment is relief of symptoms not antibiotics

41
Q

Common causes of bacteraemia

A

up to one third have unknown focus of infection

42
Q

Common focus of bacteraemia and endocarditis

A

Skin infections

Post operative

Catheter related

43
Q

Bacteraemia and Endocarditis are causative agents in approx 15% of

A

septicaemias

44
Q

Pneumoia is spread by

A

Either after aspiration of oral secretions, or form blood spread

45
Q

Patients at risk of clinical syndromes

A

Cystic fibrosis

Chronic obstructive disease

Very young and very old

46
Q

Osteomyelitis is caused by and spread by

A

caused either by haematogenous spread

secondary infection after trauma

Spread from surrounding area

47
Q

What are the symptoms of Osteomyelitis and septic Arthritis

A

Symptoms of:

Localised pain over involved bone

Painful red joint, purulent aspirate. Usually large joints

High fever

48
Q

S,aureus is the primary cause of … in you children

A

of septic arthritis in young children

49
Q

Methicillin resistant S.aureus (MRSA)

What gene controls altercation of penicllin binding protein:

A

Mec A gene

50
Q

Whats the risks of Methicillin resistant S. aureus(MRSA)

A

Ranges from asymptomatic colonisation to life threatening septicaemia

51
Q

Methicillin resistant S. aureus(MRSA) requires

A

varying treatment according to site

Needs constant vigilance and control of infection measures

52
Q

Coagulase Negative Staphylococci caused by

A

Cause of opportunistic infection in susceptible individuals

53
Q

Coagulase Negative Staphylococci capsule enables

A

enables to adhere to intravenous lines Catheters

54
Q

Coagulase Negative Staphylococci Cause infection in

A

prosthetic joints

heart valves

Microbiology (13 decks)

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