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LIFE 3007 > Gram Positive Pathogens > Flashcards

Gram Positive Pathogens Flashcards

1
Q

What colour do gram positive pathogens stain with the gram test

A

Blue/Purple

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2
Q

Gram positive bacteria characteristics.

A
  1. Thick cell wall made of peptidoglycan
  2. No periplasm
  3. Lipoteichoic Acids (glycerophosphate/ribitolphosphate)
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3
Q

Give three examples of an aerobic cocci

A
  1. Staphylococcus
  2. Streptococcus
  3. Micrococcus
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4
Q

Are staphylococci catalase positive or negative?

A

Positive

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5
Q

Which staphylococci species is is coagulase positive?

A

Staphylococcus aureus

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6
Q

Where can you find S. aureus?

A

It is an opportunistic pathogen which is found mainly on
- Anterior nares, throat and groins
- skin and intestines
- formites

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7
Q

Risk factors for infection of s. aureus

A
  1. Presence of foreign body (splinter, catheter)
  2. A surgical procedure
  3. Being immunocompromised
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8
Q

S. aureus is the main cause of

A

Skin and soft tissue infections
e.g boils, carbuncles, toxic shock syndrome

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9
Q

Staphylococcus virulence factors

A
  1. Structural Components: capsule, teichoic acids
  2. Enzymes: Coagulases, nucleases, lipases
  3. Toxins and Hemolysins: alpha toxin, beta toxin, gamma toxin
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10
Q

Diagnostic tests for S. aureus

A
  1. Selective media: salt mannitol plates (red to yellow colour change)
  2. Biochemical tests: coagulase test
  3. PCR, MALDI-TOF mass spec
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11
Q

Where is s. epidermis found?

A

On the skin, in the gut and respiratory tract

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12
Q

Who are at high risk for s. epidermidis

A

IVDU
Individuals with joint replacements
neurosurgical devices

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13
Q

Why are s. epidermidis infections hard to treat?

A
  1. they produce a biofilm when implanted
  2. they are often resistant to anti-staphylococcal agents. e.g MRSE
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14
Q

What are the characteristics of the streptococcus species

A
  1. Facultative anaerobes
  2. Need CO2 for growth
  3. Non-motile
  4. Complex nutritional requirements
  5. Catalase negative
  6. Lactic acid fermenter
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15
Q

Streptococcus classification is done using three methods

A
  1. Haemolytic patterns: sheep blood agar plates
  2. Lancefield grouping
    3.Biochemical/physiological testing to distinguish species
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16
Q

Which type of haemolysis is alpha?

A

Incomplete haemolysis.

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17
Q

What type of haemolysis is a beta?

A

complete haemolysis

18
Q

What type of haemolysis is gamma haemolysis

A

No haemoylsis

19
Q

Which Lancefield group is Streptococcus pyogenes

A

Group A

20
Q

Which Lancefield group is Streptococcus agalactiae

A

Group B

21
Q

Which Lancefield group is Streptococcus pneumoniae?

A

Group O

22
Q

The diagnostic tests for streptococcus pyogenes

A
  1. PYR test
  2. Bacitracin
23
Q

What are the two types of infections GAS (group a streptococcus) can cause

A
  1. Suppurative (pus forming) eg: Scarlet fever, tonsilitis
  2. Non-suppurative e.g rheumatic fever, acute glomerulonephritis
24
Q

Which exotoxin is responsible for beta haemolysis?

A

streptolysin s

25
Q

What diseases are caused by in streptococcus aglactiae in new born children

A
  1. Meningitis
  2. Pnuemonia
  3. Sepsis

this is due to the absence of maternal protective antibodies and low complement levels as the newborns are reliant on their mother’s breast milk for antibodies

26
Q

What type of haemolysis do GBS bacteria exhibit?

A

Beta (complete haemolysis)

27
Q

Diagnostic test for S. agalatiae

A

Hippurate hydrolysis test
CAMP test

28
Q

What type of haemolysis does S. pnuemoniae exhibit?

A

Alpha (partial)

29
Q

Where does S. pnuemonia colonize

A

The mouth and pharynx (upper respiratory tract)

30
Q

What diseases are caused by S. pneumoniae?

A
  1. Pnuemonia
  2. Meningitis
  3. Otitis media
  4. Sepsis
31
Q

Diagnostic tests for S. pnuemoniae

A
  1. Insulin fermentation
  2. Lysed by bile salts
  3. Sensitive to optochin disk tests
32
Q

The pathogenic species of Bacillus?

A
  1. B. cereus
  2. B. anthracis
  3. B. thuringensis
  4. B. mycoides
33
Q

B. cereus causes what types of infection

A
  1. Food poisoning: Vomiting or diarrheal disease
  2. Ocular infection
  3. Systemic infections (sepsis, endocarditis)
34
Q

Which toxins cause eye destruction in B. cereus

A
  1. Necrotic toxin
  2. Cerolysin
  3. Phospholipase C
35
Q

What are the diagnostic tests for Listeria monocytogenes

A

CAMP Test (positive)
Blood agar plates (beta heamolysis)

36
Q

Sources of listeria monocytogenes

A

soft cheese
milk
undercooked meat
unwashed raw vegetables

37
Q

What neonatal diseases does listeria monocytogenes cause?

A

Early onset: spontaneous abortion
Late onset: meningitis or sepsis

38
Q

What diseases does listeria monocytogenes cause in adults?

A

Influenza like illness, listeriosis

39
Q

The two pathogenic species of Mycobacterium

A
  1. Mycobacterium tuberculosis
  2. Mycobacterium leprae:lepra
40
Q

Diagnostic test for mycobacterium

A

Acid fast stain

LIFE 3007 (6 decks)

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