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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
What does the staphylococcal enzymes do Catalase
catalyses the conversion of toxic h202 to water and oxygen
26
What does the staphylococcal enzymes do - Hyaluronidase
- Breaks down hyaluronic acids in connective tissue | - Helps spread of bacteria through tissues
27
What do all staphylococci all produce
Catalase
28
what do 90% of Staphylococcal Enzymes
hyaluronidase
29
what does fibrinolysin (staphylokinase):
dissolves fibrin clots
30
Lipases:
To hydrolyse lipids and ensure survival in sebaceous areas
31
All s,aureus and 30% CNS produce ...
lipases
32
Nucluease DNase is what stable
thermostable
33
Penicillinase Beta-Lactamase production on
transmissible plasmids
34
Epidemiology
``` Ubiquitous Spread by: -shedding - Direct contact - Fomites ``` Major source of hospital acquired infection Lysozyme in tears etc forms natural barrier
35
Staphylococall scaled syndrome symptoms
redness and inflammation around the mouth covers entire body in 2 days Blisters contain clear fluid - No wbc or bacteria bu
36
Staphylococall scaled syndrome symptoms
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
Skin infections caused by staph aureus
Impetigo folliculitis (styes) Furuncles (Boils) Carbuncles Abscesses Wound infections - Skin colonising bacteria gain entry to wound Cellulitis and infection of ulcers
38
Toxic shock syndrome is associated with
local growth of S. aureus in wound or vagina and release of toxin into blood increased risk associated with retained tampons
39
Staphylococcal food poisoning Most commonly infected foods are contamination by,,, toxic is ,,, stable
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
Staphylococcal Food poisoning symptoms symptoms time treatment
Rapid onset 4 hours rapid course 24 hours Severe: - vomiting - Diarrhoea - Abdo pain - Nausea Treatment is relief of symptoms not antibiotics
41
Common causes of bacteraemia
up to one third have unknown focus of infection
42
Common focus of bacteraemia and endocarditis
Skin infections Post operative Catheter related
43
Bacteraemia and Endocarditis are causative agents in approx 15% of
septicaemias
44
Pneumoia is spread by
Either after aspiration of oral secretions, or form blood spread
45
Patients at risk of clinical syndromes
Cystic fibrosis Chronic obstructive disease Very young and very old
46
Osteomyelitis is caused by and spread by
caused either by haematogenous spread secondary infection after trauma Spread from surrounding area
47
What are the symptoms of Osteomyelitis and septic Arthritis
Symptoms of: Localised pain over involved bone Painful red joint, purulent aspirate. Usually large joints High fever
48
S,aureus is the primary cause of ... in you children
of septic arthritis in young children
49
Methicillin resistant S.aureus (MRSA) What gene controls altercation of penicllin binding protein:
Mec A gene
50
Whats the risks of Methicillin resistant S. aureus(MRSA)
Ranges from asymptomatic colonisation to life threatening septicaemia
51
Methicillin resistant S. aureus(MRSA) requires
varying treatment according to site Needs constant vigilance and control of infection measures
52
Coagulase Negative Staphylococci caused by
Cause of opportunistic infection in susceptible individuals
53
Coagulase Negative Staphylococci capsule enables
enables to adhere to intravenous lines Catheters
54
Coagulase Negative Staphylococci Cause infection in
prosthetic joints heart valves

Microbiology (13 decks)

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