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Microbiology > Identification of Gram Negative Bacilli > Flashcards

Identification of Gram Negative Bacilli Flashcards

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1
Q
  • based on phenotypic characteristics
A

Biochemical testing

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2
Q

use of antibodies to detect expressed proteins on a bacterium

A

Serotyping

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3
Q

Carbohydrate utilization

A
  • lactose or glucose degradation

- traditional test for Gram-negative bacteria

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4
Q

lactose degradation

A
  • consists of glucose and galactose
  • requires two enzymes: beta-galactoside permease and beta-galactosidase
  • slow lactose fermenters lack permease
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5
Q

Oxidation

A

utilize carbohydrates aerobically; glycolysis pathway (glucose to pyruvate to CO2)

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6
Q

Fermentation

A

utilize carbohydrates anaerobically; glycolysis pathway (glucose to pyruvate to acid)

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7
Q

asaccharolytic

A

do not utilize carbohydrates

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8
Q

O/F Basal media

A

lower peptones; aerobic and anaerobic tubes

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9
Q

O/F Media (positive for fermentation)

A

yellow throughout in both tubes due to acid production from fermentation under anaerobic conditions

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10
Q

O/F Media (positive for oxidation)

A

aerobic tube (O2) is yellow at top indicating oxidative glucose utilization; anaerobic tube remains green

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11
Q

O/F Media (negative for glucose utilization)

A

no color change in either tube

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12
Q
  • contains glucose, lactose and sucrose
  • much more lactose and sucrose than glucose (10:1)
  • similar to KIA (no sucrose)
  • ferrous sulfate and sodium thiosulfate (detects H2S)
  • phenol red indicator
  • slant is aerobic, butt is anaerobic
A

Triple Sugar Iron Agar (TSI)

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13
Q

Interpreting TSI

A

read as slant/butt

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14
Q

No fermentation (TSI)

A

K/K

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15
Q

Glucose fermentation (TSI)

A

K/A

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16
Q

Glucose then sucrose or lactose fermentation (TSI)

A

A/A

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17
Q

Hydrogen sulfide (TSI)

A

black precipitate from acid and thiosulfate

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18
Q

Gas production (TSI)

A

causes bubbles or splitting in media

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19
Q

Ortho-Nitrophenyl-beta-D-Galactopyranoside (ONPG) test

A
  • tests for slow lactose fermenters
  • ONPG is transported easily into bacterial cells
  • hydrolyzes ONPG to galactose and O-nitrophenol (yellow)
  • non lactose fermenters are clear
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20
Q

Methyl Red and Voges-Proskaur (MRVP) Test

A

tests glucose metabolic method

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21
Q

Glucose metabolized by mixed acid pathway (MRVP)

A

methyl red positive

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22
Q

Glucose metabolized by butylene glycol pathway (MRVP)

A

Voges-Proskaur positive; produces butylene glycol and acetoin

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23
Q

Decarboxylase test

A
  • tests for presence of enzymes that can remove COOH

- specific for lysine, ornithine and arginine

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24
Q

Lysine decarboxylase

Study These Flashcards
A

Lysine –> cadaverine + CO2

25
Ornithine decarboxylase
Ornithine --> putrescine
26
Dihydrolase test
degrades arginine to ornithine | arginine --> citrulline --> ornithine --> putrescine
27
Lysine Iron Agar (LIA) Slant
contains lysine, glucose, ferric ammonium citrate, sodium thiosulfate pH indicator is bromcresol purple primary function of test is deamination or decarboxylation of lysine; can also detect H2S
28
Deamination of lysine (LIA)
reddish color
29
Decarboxylation of lysine (LIA)
remains purple
30
amino acids are metabolized by deaminases that remove amine groups includes PAD test for differentiation of Proteus, Morganella, and Providencia
Deaminase test
31
deamination produces phenylpyruvic acid | add 10% ferric chloride (green is positive)
Phenylalanine deaminase (PAD) test
32
Citrate utilization
tests for organisms that use citrate as a sole carbon source results in alkaline pH (color changes to blue +) inoculum must be light
33
DNase
endonucleases that can break down phosphodiester bonds | streak to plate and add 1N HCl; clear halo is positive
34
Gelatin liquefication
Gelatinase production causes a loss of gelling (media is no longer solid in the tube)
35
Indole test
Tryptophanase produced by organisms breaks down tryptophan to indole includes Ehrlich's indole test and Kovac's test
36
Ehrlich's indole test
add Ehrlich's reagent (PDAB) - positive is red color | indole is extracted by xylene
37
Kovac's test
add Kovac's reagent; red color is positive
38
Malonate utilization test
tests whether malonate is the sole carbon source for an organism turns from green to blue when positive (bromothymol blud)
39
Motility test
observes growth in semisolid media stab a single line and observe growth away from line Kleb, Yersinia and Shigella are non-motile at 37C
40
Reduction of Nitrate (NO3) to Nitrite (NO2)
add NNDN or N,N-dimethyl-1 napthylamine, look for red or gas production nitrate --> nitrite + sulfanilic acid + NNDN --> diazo red dye if red, add Zinc, if red color, nitrate was not reduced (test verification)
41
Oxidase test
determines presence of cytochrome oxidase (dimethyl-paraphenyl-dihydrochloride) positive if purple
42
Urease test
determines organisms ability to hydrolyze urea --> ammonia, water and CO2 bright pink is positive
43
Combo tests
``` LIA (lysine differentiates Shigella and Salmonella) MIO agar (Motility-indole-ornithine agar - differentiates Serratia and Enterobacter) SIM media (Sulfide-indole-motility medium) ```
44
Manual Multitest Systems (all tests based on these principles)
``` pH-based reactions enzyme-based reactions utilization of carbon sources detection of bacterial growth detection of volatile fatty acids ```
45
Rapid Identification Systems
faster than conventional method based on carbohydrate utilization or chromogenic substrates change color quickly due to amplification of tests
46
TSI Biochemical Reaction for: | Escherichia
A/A | indole +
47
TSI Biochemical Reaction for: Proteus
A/A H2S+ | urea +, deam +
48
TSI Biochemical Reaction for: | Salmonella
K/A H2S+ | mal-, ONPG-
49
TSI Biochemical Reaction for: | Shigella
K/A | citrate -, non-motile
50
TSI Biochemical Reaction for: | Pseudomonas
K/K | ox +, blue-green pigment, growth at 42 degrees C, growth in cetrimide
51
TSI Biochemical Reaction for: | Enterobacter
A/A | ODC +, sugars
52
TSI Biochemical Reaction for: | Arizona
A/A, H2S+ | LDC +
53
TSI Biochemical Reaction for: | Citrobacter
K/A or A/A, H2S+ | LDC-
54
TSI Biochemical Reaction for: | Providencia
K/A | deam +
55
TSI Biochemical Reaction for: | Klebsiella
A/A | ODC-
56
TSI Biochemical Reaction for: | Edwardsiella
K/A, H2S+ | indole +, LDC +
57
TSI Biochemical Reaction for: | Serratia
A/A | sugars
58
TSI Biochemical Reaction for: | Proteus
K/A | urea +, deam +
59
TSI Biochemical Reaction for: | Yersinia
K/A | small colonies, urea +, deam -

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