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MicrobiLOLogy > Staphylo'cocc'us and Strepto'cocc'us > Flashcards

Staphylo'cocc'us and Strepto'cocc'us Flashcards

1
Q 
Staph and Strep share some common characteristics:
Gram + or -?
Aerobic or anaerobic?
Spore-forming? 
Motile? 
What kind of infections do they cause? 
Where are they commensals on the body?
A 
Gram positive
Facultative Anaerobes
Non spore-forming
Non motile
Cause supparative, pyogenic infections
Commensals of mucous membranes and skin
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2
Q

How would you describe the texture of their magical pus?

A

Staph- thick and CREAMY

Strep- thin and serous

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3
Q

Describe staph/strep colonies

A

Staph- Opaque, creamy colonies

Strep- Translucent, greyish colonies

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4
Q

Which of staph/strep will produce catalase?

A

STAPH WOOO!

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5
Q

Which of staph/strep will grow on both MacConkey and Nutrient agar?

A

Staph, he survives well in the environment and is resistant to bile salts- STAPHIA MAFIA
Strep is sensitive to bile salts and won’t grow on Nutrient agar- Strep is a pussy.

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6
Q

Which of staph/strep form grape-like colonies, clusters due to incomplete divisions?

A

Staph- he is cool and mafia so he keeps his friends close
Strep form long chains. Awkward strep chains. His main strategy for life is to avoid phagocytosis because he does not like personal contact.

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7
Q

Give 3 strategies of extracellular pathogens

A

Counteract complement
Counteract phagocytes
Acquire nutrients

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8
Q

Name 4 staphylococci of veterinary importance

A

S. aureus
S. pseudintermedius
S. hyicus
S. epidermidis

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9
Q

Which of the 4 staphylococci of veterinary importance is this?
Golden colonies
Lactose Fermenter
Alpha and Beta toxins- haemolysis

A

S. aureus

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10
Q

Which 4 tests would you carry out to differentiate pathogenic from non pathogenic Staphylococci ?
Which two species are positive for all 4 tests?

A

Coagulase
Catalase
DNAase
Haemolysis
S.aureus and S. pseudintermedius are positive for everything (sluts)
Non- pathogenic strains are only positive for catalase

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11
Q

Does Alpha toxin cause complete or incomplete haemolysis?

A

Complete

Beta causes incomplete

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12
Q

To differentiate between pathogenic strains of Staph, use biochemistry, API Staph. What does API stand for?

A

Analytical Profile Index

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13
Q

Describe the Coagulase Test

A

Fibrinogen (soluble) + coagulase –> fibrin clot (insoluble)

Clot formation= POSITIVE

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14
Q

Describe the DNAase Test

A

DNA is impregnated into the medium, it shows as a white precipitate. If DNAase is present in the sample, the medium will turn clear around the colonies

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15
Q

Neutrophil extracellular traps (NETs)

A

Neutrophils explode upon prolonged contact with bacteria, in order to externalise their contents and engulf the surrounding bacteria. Pathogenic staphs (and streps) make DNAase to stop this from harming them- they can escape NETs

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16
Q

Staph Virulence Factors (6)

A 
Adherence
Anti-chemotaxis
Anti-opsonic & anti-phagocytic
Iron-uptake systems
Degradative enzymes
Toxins
17
Q

Staphylococcal resistance to phagocytosis, what mechanism is used?

A
  1. Binding of the Fc portion of antibody to Protein A
  2. Staphylococcal complement inhibitor (SCIN) inhibits all complement (C’) ativation pathways
  3. Capsule production- the capsule activates and binds complement, but it is not opsonised or phagocytosed
  4. Fibrinogen binding protein- surface bound fibrinogen. Inhibits opsonisation
  5. Haemolysins and leukocidin- Inhibit or lyse phagocytes
18
Q

ET COME HOOOOME! What does ET stand for?

A 
Exfoliative toxin 
S.aureus – at least 4 ET
Protease – cleaves desmoglein 1 in desmosomes
Separation of the upper epidermis 
S.hyicus 
At least 5 ET
S.pseudintermedius
A ET-like toxin has been described
19
Q

Antigens stimulate < 0.01% of T cells

How much do SuperAntigens stimulate?

A

Stimulate 2-20 % of T cells, leads to
Massive release of pro-inflammatory cytokines then shock
S.aureus and Streptococcus pyogenes produce many SA

20
Q

Streptococci- two types of haemolysis Alpha and Beta- appearance?

A

Alpha- If zone is darker than the media/ green. This leaves the RBCs intact but causes the Hb to change colour. More pronounced on heated blood agar plates.

Beta- clear, yellow zone around the colonies of the bacterium, due to the action of haemolysins that lyse the RBCs, liberating the Hb which can then diffuse away from the area.
Complete- clear
Incomplete- opaque and fuzzy

21
Q

How do you type Strep?

A

Lancefield typing – place streptococci in (Lancefield) groups –A, B, C etc
Based on differences in carbohydrate antigen in cell wall.
Use antisera against different antigens to type

22
Q

Pathogenicity Factors of Pyogenic B-haemolytic streptococci

A 
Adherence to epithelium
Anti-chemotaxis
Systemic Toxicity- super antigens
Anti-opsonic and anti-phagocytic factors
Degradative Enzymes
23
Q

What are the 3 most common causes of Bovine Mastitis?

A

S. uberis 28%
Staphylococcus aureus 25%
E. coli 25%

24
Q

S. uberis, S. agalactiae, S. dysgalactiae- Three streps that cause mastitis. Which are environmental and which is contagious?

A

S. agalactiae is contagious, the others are environmental.

25
Q

On Edward’s Media, what is the appearance of:
S. uberis,
S. agalactiae,
S. dysgalactiae

A

S. uberis- brown, Beta-haemolytic
S. agalactiae- white translucent colonies, Alpha-haemolysis
S. dysgalactiae- green/grey colonies, incomplete Beta-haemolysis

26
Q

S. zooepidemicus and S. equi affect which species?

A

Horse

27
Q

S. zooepidemicus:

A

Nasopharyngeal commensal
Opportunistic e.g. 2° respiratory infections; wound; metritis; etc.
Infects various host species: cattle, sheep, dogs, etc.
Can cause zoonotic infections

28
Q

S. equi

A 
Pharyngitis
Lymphadenitis
Fever, swollen lymph nodes, discharge - STRANGLES
Host Specific
Septicaemia (fatal) - BASTARD STRANGLES
Highly contagious:
Quarantine & antibiotic treatment
29
Q

Virulence Factors of S.equi (4)

A

Two fibronectin binding proteins- Adhesion

Two M-like proteins- SeM, SzPSe
Anti-phagocytic, anti-opsonic.
SzPSe present in S.zooepidemicus
SeM more important

Hyaluronic acid capsule
Anti-phagocytic
Non-immunogenic

Toxins
Streptolysin S (SLS)-like toxin, anti-phagocytic 
Four Super Ags - ? Systemic effects, interfere with immune response
30
Q

Enterococci

A 
Commensals in gut of humans and animals 
Resistant to Bile Salts
Grow on MacConkey agar
Opportunist pathogens in all species
Bacteraemias in immunosuppressed animals and people
Often very resistant to antibiotics

MicrobiLOLogy (3 decks)

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