Chapter 8: Colony Morphology Flashcards

1
Q

Primary plating:

A

inoculation of clinical specimen onto laboratory culture media

Media used: selective, differential, grow fastidious organisms

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2
Q

Plate reading:

A

Observe colony morphology and compare

  • usually 18-24 hours post culture
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3
Q

Blood agar:

A

morphology, grows most organism

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4
Q

Chocolate agar:

A

most organism and fastidious organisms

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5
Q

MacConkey Agar:

A

gram-negative, particular enterics

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6
Q

Lactose fermenters are:

A

pink

Escherichia coli/Citrobacter: dry pink colonies

Klebsiella/Enterobacter-like organisms: large mucoid pink colonies

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7
Q

Nonlactose fermenters are:

A

colorless

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8
Q

Colony characteristics:

A
  • Hemolysis
  • Size
  • Form or Margin
  • Elevation
  • Density
  • Color
  • Consistency
  • Pigment
  • Odor
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9
Q

Blood agar is most important in presumptive identification of

A

streptococci and enterococci

  • must use transillumination to determine
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10
Q

beta hemolysis:

A

complete clearing of blood cells around the colonies

Examples: Streptococcus pyogenes, Streptococcus
agalactiae, Listeria monocytogenes

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11
Q

alpha hemolysis:

A

partial clearing of blood that results in a green discoloration of the medium

Examples: Streptococcus pneumoniae, certain viridans strep

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12
Q

Non-hemolytic colonies are sometimes referred to as

A

gamma hemolytic

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13
Q

Colony Size:

A

Large, medium, small, or pinpoint

– Helps suggest what you might find on Gram stain
– Gram-positive is generally smaller than gram- negative
– Staphylococcus is generally larger than Streptococcus

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14
Q

Form or Margin:

A

Swarming: hazy blanket of growth on surface (ex. proteus spp.), shows movement of bacteria

Bacillus anthracis is filamentous; diphtheroid colonies have rough edges

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15
Q

Elevation:

A
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16
Q

Umbilicate example

A

S. pneumoniae (if no capsule)

17
Q

Umbonate example:

A

diphtheroids

18
Q

Density:

A

Transparent, translucent, opaque

– Most β-hemolytic strep translucent (except group B)

– Group B strep: semiopaque (bull’s-eye colony)

– Opaque includes most staph and gram-negative
rods

19
Q

Color:

A

White, gray, yellow, buff

– Coagulase negative staph are white.
– Enterococcus and most gram-negative rods are gray.
– Micrococcus and Neisseria are yellow or off-white.
– Diphtheroids are buff

20
Q

Consistency:

A

Determine by touching a colony with a loop

Brittle (splinters), creamy, dry, waxy, or sticky
(entire colony comes off the plate)

– S. aureus: creamy
– Neisseria: sticky
– Nocardia: brittle
– Streptococci: dry
– Diphtheroid: dry and waxy

21
Q

Pseudomonas aeruginosa pigment:

A

green or green metallic sheen

22
Q

Serratia marcescens pigment:

23
Q

Kluyvera pigment:

24
Q

Chromobacterium violaceum pigment:

25
Q

Prevotella melaninogenica pigment:

A

brown-black anaerobe

26
Q

Staphylococcus aureus odor:

27
Q

Pseudomonas aeruginosa odor:

A

fruity or grapelike

28
Q

Proteus mirabilis odor:

29
Q

Haemophilus spp. odor:

A

musty basement

30
Q

Nocardia spp. odor:

A

freshly plowed field

31
Q

Organisms in Liquid Media: Streamers

A

Vinelike growth(A) in media, puff-ball–like (B)

ex. Streptococci

Scum-like growth: yeast, pseudomonas

32
Q

Organisms in Liquid Media: Turbidity

A

– Overall cloudiness of liquid
– Gas bubbles present (arrow)
* Enterics

33
Q

Organisms in Liquid Media: Microaerophilic growth

A

some yeasts