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Y2 MicroB > 15. Staph & Strep > Flashcards

15. Staph & Strep Flashcards

1
Q

Name 2 genuses of gram +ve cocci:

A
  1. Staphylococci
    - gram -ve anaerobic bacteria
  2. Streptococci
    - gram +ve aerobic bacteria
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2
Q

How do you identify gram +ve cocci under the microscope?

A
  1. Stained purple/dark blue
    => gram +ve
  2. Round shaped
    => cocci
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3
Q

How do you identify Staph. Aureus under the microscope?

A

When u see gram +ve cocci in CLUSTERS

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4
Q

How does Streptococci look like under the microscope?

A
  1. Gram +ve cocci in long chains, e.g. beta haemolytic strep
  2. Gram +ve cocci in pairs, e.g. strep pneumoniae
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5
Q

How are bacteria categorised based on their ability to induce haemolysis on blood agar?

A
  1. Alpha-haemolytic
    - partial breakdown of RBC
    - greenish appearance on blood agar
  2. Beta-haemolytic
    - complete breakdown of RBC
    - blood agar plate looks transparent cuz RBCs are broken
  3. Gamma-haemolytic/non-haemolytic
    - no breakdown of RBC, blood agar remains red
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6
Q

What is Group A strep?

A

Strep pyogenes
1. β-haemolytic streptococci
2. Aka flesh eating bug, necrotising

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7
Q

What is Group B Strep?

A

Strep. Agalactiae

  1. β-haemolytic strep
  2. Problem in pregnant women, carried in vagina
    - vertical transmission to baby => baby gets meningitis or sepsis => death
    - management: give antibiotics to mother b4 to kill bacteria b4 birth of child
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8
Q

What kind of Strep is Strep pneumoniae?

A
  • α-haemolytic strep
  • partial breakdown of RBC
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9
Q

What does Strep viridans/Viridans Streptococci refer to?

A
  • large group of commensal streptococcal gram +ve bacteria
  • α-haemolytic, ‘viridans’ means green, refers to green discolouration produced on blood agar plate

Note! Strep viridans is not a species!!

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10
Q

What does Impetigo refer to?

A

Impetigo: soft tissue infection of peri-oral region

Usually occurs:
1. In children
2. Appears as honey crusted lesions ard oral cavity

Caused by: Staph Aureus (β-haemolytic)

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11
Q

Staphylococcus Aureus is _-haemolytic.

A

β-haemolytic

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12
Q

What is Intertrigo?

A

Intertrigo: common inflammatory skin condition that is caused by skin-to-skin friction (rubbing)/overlapping skin that is intensified by heat and moisture

Common causes: Staph aureus + secondary candida infection

  • common as baby rash or in the obese/diabetics/pxs w weakened immunity system due to underlying medical disease
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13
Q

What is Lymphagitis & what is it caused by?

A

Lymphangitis: inflammation of lymphatic channels due to infectious or non-infectious causes

  • can be caused by Grp A strep (β-haemolytic strep)
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14
Q

List the conditions/infections commonly caused by Grp A strep.

A
  1. Necrotising fasciitis (type 2)
  2. Erysipelas
  3. Lymphangitis
  4. Gas gangrene (myonecrosis)
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15
Q

What is Necrotising Fasciitis?

A

TLDR: flesh eating bug, caused by Grp A strep

Hallmark symptom:
- when area is touched, elicitis severe severe pain even tho it seems like nothing serious on the surface

Why so?
- necrosis starts in the fascia, which is quite deep and cannot be seen at first
- by the time it develops toward epidermis n black necrotic material can be seen => too late
- seen 1 or 2 times a yr (quite rare), dangerous cuz medical professionals may dismiss condition at first if they r not alert

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16
Q

Name some conditions commonly caused by Staph Aureus?

A
  1. Osteomyelitis
  2. Septic arthritis
  3. Cellulitis
  4. Intertrigo
17
Q

What is Osteomyelitis commonly caused by? How is it managed?

A

Staph Aureus.
Prescribed weeks to months of IV antibiotics => must be hospitalised or sent home w an IV access

18
Q

What is Septic Arthritis and what is it commonly caused by?

A

Septic Arthritis: infection of joint, either monoarticular or polyarticular

Typical pathogen: Staph Aureus

Symptoms: painful, red, hot joint, swelling, fever

19
Q

What is Endocarditis and what is it’s common cause?

A

Endocarditis: infection of heart valves/ life-threatening inflammation of the inner lining of the heart’s chambers and linings
=> observe bacterial deposit at heart valves

Commonly due to: α-haemolytic strep (partial breakdown of RBC)
- could be due to staph aureus too

Tx: requires weeks of antibiotics OR even replacement of heart valves

20
Q

What is MRSA?

A

MRSA: Methicillin resistant staph aureus.

21
Q

How should MRSA be treated?

A

DO NOT GIVE: cloxicillin
- cloxicillin is the usual to go antibiotic for standard staph aureus

HOWEVER,
- MRSA is resistant to most beta-lactam antibiotics including cloxicillin
- will help the MRSA colonise => eventually kills px

INSTEAD,
- can give vancomycin (esp when in severe cases/dying) & minocycline & tetracycline otherwise
- downside: vancomycin only administrable via IV

Y2 MicroB (25 decks)

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