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Infectious Diseases > ORGANISMS - STREPS > Flashcards

ORGANISMS - STREPS Flashcards

1
Q

What gram is a streptococcus?

A

GRAM POSITIVE

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2
Q

How are they arranged?

A

ARRANGED IN CHAINS, STAPHS IN CLUMPS

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3
Q

Are they catalase +ve or -ve?

A

NEGATIVE

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4
Q

Are they anaerobic or aerobic?

A

ANAEROBIC

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5
Q

Give the names of the 3 types of classification and describe the breakdown of blood agar for each type

A

ALPHA HAEMOLYSIS - viridans group, partial breakdown (green)
BETA HAEMOLYSIS - most common, complete breakdown
GAMMA HAEMOLYSIS - enterococci, no break down, no clear space.

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6
Q

Why cant haemolysis occur on chocolate agar?

A

Haemolysis is break down of blood, and in chocolate agar this has already occured. results would always look green.

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7
Q

Give examples of a typical case patient for Strep. pneumoniae infection

A

Elderly, cough, chest pains, purulent sputum, chill and developed fever, high temp

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8
Q

How to diagnose Strep. pneumoniae

A
  • Easy to spot in sputum smear
  • Quelling reaction - anticapsular antibodies cause capsule to swell, easily visible.
  • Dimpled colonies.
  • Optochin sensitive - only strep is sensitive to this
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9
Q

What are the most medically important Lancefield groups?

A

A,B and D

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10
Q

Why cant Strep. Pneumoniae and Strep. viridans be identified in Lancefield grouping?

A

This method is only for beta haemolytic streps and they are both alpha haemolytic

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11
Q

Give 2 examples of non-invasive Strep. pyogenes infections

A

ANY FROM pharyngitis (strep throat), impetigo, scarlet fever, cellulitis

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12
Q

Give 2 examples of invasive Strep. pyogenes infections

A

ANY FROM toxic shock type syndrome, necrotising fasciiitis, rheumatic fever, glomerulonephritis

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13
Q

Give symptoms of strep throat (pharyngitis)

A

Hot, flushed, sore throat, vommiting, high temp, red throat, greyish white exudate, enlarged lymph nodes

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14
Q

Complications and Symptoms of scarlet fever

A
  • Rash
  • Strawberry tongue
  • If organism produces SPE (erythrogenic) toxin = scarlet fever
  • Rash dissapears 1 week later then skin sloughs.
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15
Q

Complications and Symptoms of rheumatic fever

A
  • Life threatening: joints, fever, heart
  • Damage to rheumatic joints
  • Damage to heart valves (scarring)
  • Autoimmune response - anti strep antibodies react with heart antigens
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16
Q

Give examples of complications of acute rheumatic fever

A
  • Fatalities - heart failure
  • Scaring of valves
  • Prevention - penicillin treatment of pharyngitits
  • Number of cross reactive agents (auto immune disease)
17
Q

What is the mode of action of Strep. pyogenes?

A
  • ATTACHMENT
  • MULTIPLICATION
  • SPREAD (all by adhesions, important in throat, pharynx infections)
  • ADHESIONS such as lipotechioic acid (LTA) M proteins
18
Q

Explain the multiplication stage of Strep. pyogenes infection.

A
  • M-protein, bind fibrinogen, fibrin and degradation products.
  • blocks complement attachment
  • binds factor H - inhibits complement cascade.
  • resistant to phagocytosis
  • nearly 100 diff m-types
19
Q

Name the 3 ways Strep. pyogenes spreads

A

SKIN - localised
PHARYNX - far as ears or sinuses
WOUND - rapid spread, aided by virulence proteins

20
Q

Name 3 of Strep. pyogenes virulence factors

A

proteases, Dnase, streptokinase, hyaluronidase

21
Q

What are the actions of streptokinase?

A
  • Induces fibrinolysis. (degrades fibrin and other proteins, affects clotting).
  • This helps to spread as clotting localises infection
22
Q

What are the actions of hyaluronidase?

A
  • breaks down hyaluronic acid in connective tissue.
  • bactiera shut off capsule production
  • turn on hyaluronidase production at epithelial surface.
23
Q

Name 3 ways in which Strep. pyogenes causes damage

A

ANY 3 FROM - pyrogenic toxins, ABC, erythrogenic toxins, suppress antibody responses, stimulate cytokines (SEPTIC SHOCK) streptolysins.

24
Q

How would Strep. pyogenes be diagnosed in a lab situation?

A
  • culture of pus and blood

- bacitracin sensitive

25
Q

Where are group B polysach. capsules found? What bacteria would be found there?

A

Lower GI and female tracts.

Strep. agalactiae ( EXTRA - NEONATAL SPESIS PLUS MENINGITIS - 10-20% FATAL)

26
Q

If a neonate succumbs to neonatal sepsis from Strep. agalactiae, how many % of survivors will be brain damaged?

A

30-50

27
Q

What can Strep. agalactiae cause?

A

cellulitis, arthritis, meningitis

28
Q

Who is most at risk for contracting Strep. agalactiae?

A

IMMUNOCOMPROMISED - elderly, diabetics, alcoholics

29
Q

What is the diagnosis and treatment for Strep. agalactiae?

A
  • bacitracin resistant
  • grouping (strep group, latex agglutination)
  • treat with penicillin, much higher concentrations that group A treatment
30
Q

What group is Strep. milleri?

A

F

31
Q

Give a description of Strep. milleri

A
  • microaerophillic/anaerobic
  • tiny colonies
  • usually abscesses in soft tissue
  • smells like toffee/caramel on agar
32
Q

What Lancefield group is Enterococci

A

TRICK Q - D but classed in separate group based on genus along with Lancefield test

33
Q

Where is enterococci found?

A

The gut

34
Q

Is Enterococci bile resistant? How many nosocomial infections does it account for?

A

YES and 10%

Infectious Diseases (3 decks)

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