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Elsevier Bacteriology (RVSP) > 1. Intro (I) > Flashcards

1. Intro (I) Flashcards

1
Q

Bacteria that are not stained through Gram Staining

A

Chlamydia
Legionella
Mycoplasma

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2
Q

Gram stain procedure

A

Crystal violet (1° stain)
Gram’s iodine (Mordant)
Acetone / alcohol (Decolorizer)
Safranin (Counterstain)

COAM

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3
Q

What is the difference between Gram+ and Gram- cell walls?

A

Cell walls of gram-negative cells have higher lipid content that gram-positive cells

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4
Q

Special consideration of Gram Stain of sputum specimen; if >25 epithelial cells/lpf

A

Saliva

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5
Q

Special consideration of Gram Stain of sputum specimen; few epithelial cells, many PMN cells

A

Specimen more likely to yield a pathogen

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6
Q

When can you say that a sputum specimen is actually saliva?

A

When there are >25 epithelial cells/lpf

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7
Q

When can you say that a sputum specimen may likely yield a pathogen?

A

When there are few epithelial cells and many PMN cells

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8
Q

Special consideration for urine specimen

A

1 cell per oil immersion field = approx. 1x10^5 CFU/mL

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9
Q

Enumerate the quantitation criteria for Gram Stain

A
  • no organisms seen
  • Few per slide = rare
  • 0 to 2 per field = few
  • 2 to 10 per field = moderate
  • more than 10 per field = many
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10
Q

Constituents of media

A 
Agar
Nutrients
Enrichments
Buffers
pH indicators
Inhibitors

BEANpI

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11
Q

Constituent of media; gelatinous seaweed extract

A

Agar

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12
Q

Percent of agar in plates

A

1-2% agar in plates

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13
Q

Nutrients in media can be _______ or _______

A 
Hydrolyzed proteins (animal or plant)
Carbohydrates/sugars
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14
Q

Enrichments used in media

A

Yeast extracts

Blood

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15
Q

Purpose of buffers in media

A

Provides a stable pH for growth

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16
Q

pH indicators used in media and their colors

A

Neutral red: red to colorless
Phenol red: yellow to red
Thymol blue: yellow to green/blue

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17
Q

Inhibitors in media

A 
Bile salts
Antibiotics
Dyes
Sodium chloride
Sodium citrate

BADSS

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18
Q

Examples of dyes used as inhibitors in media

A

Crystal violet
Eosin
Methylene blue

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19
Q

Example of bile salt used as inhibitor in media

A

Sodium deoxycholate

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20
Q

Agar that contains inhibitory agents to all organisms except one being sought

A

Selective agar

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21
Q

Example of selective agars

A

Colistine nalidixic acid agar (CNA)

MacConkey Agar

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22
Q

Agar that selects for certain organisms to the disadvantage of others

A

Selective agar

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23
Q

Agar that allows organism to be morphologically distinguished from other organisms with different characteristics

A

Differential agar

24
Q

Examples of differential agar

A

Sheep blood agar (SBA)

MacConkey agar

25
Q

Supportive media aerobic cultures

A

Blood agar

Chocolate agar

26
Q

Selective/differential media for gram-negative aerobic bacilli

A

MacConkey agar
Xylose Lysine Desoxycholate (XLD) agar
Hektoen Enteric Agar (HEA)

27
Q

Selective/differential media for gram-positive aerobic organisms

A

Colistin Nalidixic Acid (CNA) agar

Phenylethyl Alcohol Agar (PEA)

28
Q

Purpose of Blood Agar for aerobes

A

General growth of gram-positive and gram-negative aerobes

29
Q

Why is the Blood Agar also considered as differential aside from being supportive?

A

Because organisms may demonstrate hemolytic patterns

30
Q

Chocolate agar is used for

A

Isolation of fastidious organisms:

  • Haemophilus spp.
  • Neisseria spp.
  • Brucella spp.
  • Capnocytophaga spp.
31
Q

Components of MacConkey agar

A

Lactose
Crystal violet
Bile salts

32
Q

pH indicator in MacConkey agar

A

Neutral red

33
Q

Purpose of lactose in MacConkey agar

A
  • Provides fermentable sugar (Lactose positive vs negative)

- Lactose fermenting vs non-lactose fermenting organism

34
Q

Purpose of crystal violet in MacConkey agar

A

Inhibits gram-positive bacteria

35
Q

Purpose of bile salts in MacConkey agar

A

Inhibits gram-positive bacteria

36
Q

MacConkey agar is selective for

A

Gram-negative organisms

37
Q

Lactose positive bacteria (lactose fermenters)

A 
Escherichia coli: dry, flat, dark pigment
Enterobacter: mucoid
Citrobacter: late fermenter
Klebsiella: mucoid
Serratia: late, red pigment (some)

EECKS

38
Q

Lactose negative bacteria (non-lactose fermenters)

A 
Proteus: swarming
Providencia
Pseudomonas
Hafnia
Edwardsiella
Morganella
Salmonella
Shigella

P3HEMS2

39
Q

Component of XLD; inhibits gram-positive organisms

A

Sodium deoxycholate

40
Q

pH indicator of XLD

A

Phenol red

41
Q

Carbohydrate components in XLD

A

Lactose
Sucrose
Xylose

42
Q

Carbohydrates in XLD that provide fermentable sugar

A

Lactose

Sucrose

43
Q

Enzyme detected by lysine in XLD agar

A

Lysine decarboxylase

44
Q

Effect of Salmonella to lysine in XLD agar

A

Since Salmonella has lysine decarboxylase, the lysine in the agar is decarboxylated, shifting the pH indicator to red

45
Q

Component of XLD; detects production of H2S

A

Sodium thiosulfate

Ferric ammonium citrate

46
Q

Characteristics of E. coli in XLD

A

Yellow color; ferments carbohydrates; causes large pH drop

47
Q

Characteristics of Shigella and Providencia in XLD

A

Colorless or red; no fermentation; no H2S

48
Q

Characteristics of Salmonella in XLD

A

Red with black center; ferments xylose; produces low pH; then decarboxylates lysine; produces high pH; H2S production

49
Q

Purpose of sodium deoxycholate in XLD

A

Inhibits gram-positive organisms

50
Q

Organism(s) that ferments carbohydrates in XLD, causes large pH drop, yellow color

A

E. coli

51
Q

Organism(s) that is/are colorless or red in XLD; no fermentation, no H2S production

A

Shigella

Providencia

52
Q

Organism that produce red color with black center in XLD, ferments xylose, produces low pH, then decarboxylates lysine, produces high pH, H2S production

A

Salmonella

53
Q

What is the X factor in the chocolate agar?

A

Hemin

IsoVitaleX Enrichment (according to Elsevier reviewer)

54
Q

What is the V factor in the chocolate agar?

A

Nicotinamide adenine dinucleotide (NAD)

Hemoglobin (according to Elsevier reviewer)

55
Q

Developer of Gram Stain

A

Hans Christian Gram (1884)

Elsevier Bacteriology (RVSP) (34 decks)

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