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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
Supportive media aerobic cultures
Blood agar | Chocolate agar
26
Selective/differential media for gram-negative aerobic bacilli
MacConkey agar Xylose Lysine Desoxycholate (XLD) agar Hektoen Enteric Agar (HEA)
27
Selective/differential media for gram-positive aerobic organisms
Colistin Nalidixic Acid (CNA) agar | Phenylethyl Alcohol Agar (PEA)
28
Purpose of Blood Agar for aerobes
General growth of gram-positive and gram-negative aerobes
29
Why is the Blood Agar also considered as differential aside from being supportive?
Because organisms may demonstrate hemolytic patterns
30
Chocolate agar is used for
Isolation of fastidious organisms: - Haemophilus spp. - Neisseria spp. - Brucella spp. - Capnocytophaga spp.
31
Components of MacConkey agar
Lactose Crystal violet Bile salts
32
pH indicator in MacConkey agar
Neutral red
33
Purpose of lactose in MacConkey agar
- Provides fermentable sugar (Lactose positive vs negative) | - Lactose fermenting vs non-lactose fermenting organism
34
Purpose of crystal violet in MacConkey agar
Inhibits gram-positive bacteria
35
Purpose of bile salts in MacConkey agar
Inhibits gram-positive bacteria
36
MacConkey agar is selective for
Gram-negative organisms
37
Lactose positive bacteria (lactose fermenters)
``` Escherichia coli: dry, flat, dark pigment Enterobacter: mucoid Citrobacter: late fermenter Klebsiella: mucoid Serratia: late, red pigment (some) ``` EECKS
38
Lactose negative bacteria (non-lactose fermenters)
``` Proteus: swarming Providencia Pseudomonas Hafnia Edwardsiella Morganella Salmonella Shigella ``` P3HEMS2
39
Component of XLD; inhibits gram-positive organisms
Sodium deoxycholate
40
pH indicator of XLD
Phenol red
41
Carbohydrate components in XLD
Lactose Sucrose Xylose
42
Carbohydrates in XLD that provide fermentable sugar
Lactose | Sucrose
43
Enzyme detected by lysine in XLD agar
Lysine decarboxylase
44
Effect of Salmonella to lysine in XLD agar
Since Salmonella has lysine decarboxylase, the lysine in the agar is decarboxylated, shifting the pH indicator to red
45
Component of XLD; detects production of H2S
Sodium thiosulfate | Ferric ammonium citrate
46
Characteristics of E. coli in XLD
Yellow color; ferments carbohydrates; causes large pH drop
47
Characteristics of Shigella and Providencia in XLD
Colorless or red; no fermentation; no H2S
48
Characteristics of Salmonella in XLD
Red with black center; ferments xylose; produces low pH; then decarboxylates lysine; produces high pH; H2S production
49
Purpose of sodium deoxycholate in XLD
Inhibits gram-positive organisms
50
Organism(s) that ferments carbohydrates in XLD, causes large pH drop, yellow color
E. coli
51
Organism(s) that is/are colorless or red in XLD; no fermentation, no H2S production
Shigella | Providencia
52
Organism that produce red color with black center in XLD, ferments xylose, produces low pH, then decarboxylates lysine, produces high pH, H2S production
Salmonella
53
What is the X factor in the chocolate agar?
Hemin IsoVitaleX Enrichment (according to Elsevier reviewer)
54
What is the V factor in the chocolate agar?
Nicotinamide adenine dinucleotide (NAD) Hemoglobin (according to Elsevier reviewer)
55
Developer of Gram Stain
Hans Christian Gram (1884)

Elsevier Bacteriology (RVSP) (34 decks)

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