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H&D > Wk 1 Clinical Bacteriology > Flashcards

Wk 1 Clinical Bacteriology Flashcards

1
Q

What is darkfield microscopy used for?

A

When organism is difficult to see with bright field
Borrelia, Treponema, Mycoplasma

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2
Q

Gram stain examples

A
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3
Q

What color are acid fast negative and positive bacteria?

A

negative = blue
positive = red

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4
Q

What do mycobacterium species cell walls contain?

A

mycolic acids, fatty acids, and lipids
-they are acid-fast positive

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5
Q

What are non-acid fast bacteria counter stained with?

A

Methylene blue

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6
Q

What does hemolysis on blood agar look like?

A
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7
Q

What are 2 types of non-selective media?

A
  1. tryptic soy broth - widely used to isolate bacteria
  2. thioglycolate broth - can differentiate b/w species based on O2 requirements
    3-anaerobic bacteria (like Gram-positive spore formers)
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8
Q

3 types of selective and differential media

A
  1. CNA agar - selects for Gram-positive bacteria (Colistin and** N**alidixic acid inhibit Gram-negative bacteria) (Gram + Staphylococcus, Streptococcus)
  2. MacConkey agar - selects Gram-negative, lactose, bile salts inhibit Gram + bacteria (differentiates lactose fermenters (pink) vs non-lactose fermenters (not pink)
  3. Thayer-Martin media - chocolate agar supplemented w/ antibiotics (used to culture and isolate Neisseria sp), Vancomycin kills Gram-positives, Trimethroprim and Colistin kill most Gram-negative organisms except Neisseria) - think Neisseria sp. with this!!
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9
Q

Common clinically important anaerobes

A
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10
Q

What are 3 biochemical tests?

A
  1. Catalase test
  2. Coagulase test
  3. Oxidase test
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11
Q

Catalase test

A
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12
Q

Coagulase Test

A
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13
Q

Oxidase Test

A
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14
Q

Oxidative-Fermentation test

A
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15
Q

TSI

A

=triple sugar iron

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16
Q

Agglutination tests

A
17
Q

What are 5 serologic tests

A

Antigensoftheorganismintissues or body fluids
* Antibodiesinpatient’sserum
Tests:
1. Agglutination (rapid)
2. Enzyme immunoassay (ELISA)
3. immunofluorescence (IF)
4. Immunohistochemistry (IHC)
5. Western blot

18
Q

Review

A
19
Q

Most common staphylococcus

A

-are catalase positive
S. aureus
S. epidermidis
S. saprophyticus

20
Q

Staphylococcus aureus

A
  • Catalase positive
  • Coagulase positive
  • β-Hemolytic
21
Q

MRSA (Methicillin-Resistant S. aureus)

A
  • Highly antibiotic resistant=SUPER BUG
  • Resistant to the penicillinase-stable penicillins (methicillin, nafcillin, and oxacillin) and all beta-lactam drugs
  • Altered penicillin-binding protein PBP2A encoded by mecA
22
Q

Staphylococcus epidermidis

A
  • Non-hemolytic
  • Catalase positive
  • Coagulase negative
  • Novobiocin sensitive
  • Normal skin flora (epidermis=skin)
  • Contaminates blood cultures
  • Skin/wound infections
  • Biofilms on plastic devices: catheters, prostheses (hip implant, heart valve)
23
Q

Staphylococcus saprophyticus

A

*Gram-positive
Catalase positive
* Coagulase negative
* Novobiocin resistant

  • Normal flora of female genital tract
  • Urinary tract infection or Uncomplicated cystitis, second most common cause
  • Peritonitis
24
Q

Streptococcus and Enterococcus

A
  • S. pyogenes (Group A Strep)
  • S. agalactiae (Group B Strep)
  • S. pneumoniae (pneumococcus)
  • Viridans Streptococci group
  • Enterococcus species
25
Q

Streptococcus classification

A
26
Q

Streptococcus agalactiae (Group B Streptococcus)

A
  • Catalase negative
  • β-hemolytic
  • Narrow zone of hemolysis
  • Bacitracin resistant
  • Lancefield Group B
  • Polysaccharide capsule is a significant virulence factor
  • Colonizes genital and lower GI tracts of 10-40% of women; also found in oropharynx, upper GI
  • Pregnant women screened at 36-38 weeks for
    GBS
  • Intrapartum penicillin prophylaxis if positive
27
Q

Streptococcus pyogenes (Group A Streptococcus, GAS)

A
  • Group A Strep, human-restricted pathogen
  • β-hemolytic
  • Bacitracin sensitive
  • Differentiate from other β-hemolytic streptococci
  • Lancefield Group A
  • Virulence factors
    – Capsule
    – M protein: Antiphagocytic, inhibits complement
    – Enzymes for tissue invasion: Streptolysin, DNAses,
    Streptokinase (dissolves clots)
    – Superantigens
28
Q

S. pyogenes (Group A Streptococcus)

A
  • Pyogenic
  • Pharyngitis*
  • Impetigo (honey crusted lesions) * Cellulitis
  • Scarlet fever (strawberry tongue)
  • Bacteremia, toxic shock-like syndrome
  • Necrotizing fasciitis
29
Q

Streptococcus pneumoniae (pneumococcus)

A
  • Lancet-shaped diplococcus * No Lancefield group
  • α hemolytic (partial)
  • Optochin sensitive
  • Differentiate from α-hemolytic Viridans Streptococci
  • Bile soluble
  • Autolysin activated by bile
    • Meningitis, otitis media, pneumonia, sinusitis
      (MOPS)

H&D (23 decks)

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