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Microbiology > Identification of Gram Negative Bacilli > Flashcards

Identification of Gram Negative Bacilli Flashcards

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

A

Lysine –> cadaverine + CO2

25
Q

Ornithine decarboxylase

A

Ornithine –> putrescine

26
Q

Dihydrolase test

A

degrades arginine to ornithine

arginine –> citrulline –> ornithine –> putrescine

27
Q

Lysine Iron Agar (LIA) Slant

A

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
Q

Deamination of lysine (LIA)

A

reddish color

29
Q

Decarboxylation of lysine (LIA)

A

remains purple

30
Q

amino acids are metabolized by deaminases that remove amine groups
includes PAD test
for differentiation of Proteus, Morganella, and Providencia

A

Deaminase test

31
Q

deamination produces phenylpyruvic acid

add 10% ferric chloride (green is positive)

A

Phenylalanine deaminase (PAD) test

32
Q

Citrate utilization

A

tests for organisms that use citrate as a sole carbon source
results in alkaline pH (color changes to blue +)
inoculum must be light

33
Q

DNase

A

endonucleases that can break down phosphodiester bonds

streak to plate and add 1N HCl; clear halo is positive

34
Q

Gelatin liquefication

A

Gelatinase production causes a loss of gelling (media is no longer solid in the tube)

35
Q

Indole test

A

Tryptophanase produced by organisms breaks down tryptophan to indole
includes Ehrlich’s indole test and Kovac’s test

36
Q

Ehrlich’s indole test

A

add Ehrlich’s reagent (PDAB) - positive is red color

indole is extracted by xylene

37
Q

Kovac’s test

A

add Kovac’s reagent; red color is positive

38
Q

Malonate utilization test

A

tests whether malonate is the sole carbon source for an organism
turns from green to blue when positive (bromothymol blud)

39
Q

Motility test

A

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
Q

Reduction of Nitrate (NO3) to Nitrite (NO2)

A

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
Q

Oxidase test

A

determines presence of cytochrome oxidase (dimethyl-paraphenyl-dihydrochloride)
positive if purple

42
Q

Urease test

A

determines organisms ability to hydrolyze urea –> ammonia, water and CO2
bright pink is positive

43
Q

Combo tests

A 
LIA (lysine differentiates Shigella and Salmonella)
MIO agar (Motility-indole-ornithine agar - differentiates Serratia and Enterobacter)
SIM media (Sulfide-indole-motility medium)
44
Q

Manual Multitest Systems (all tests based on these principles)

A 
pH-based reactions
enzyme-based reactions
utilization of carbon sources
detection of bacterial growth
detection of volatile fatty acids
45
Q

Rapid Identification Systems

A

faster than conventional method
based on carbohydrate utilization or chromogenic substrates
change color quickly due to amplification of tests

46
Q

TSI Biochemical Reaction for:

Escherichia

A

A/A

indole +

47
Q

TSI Biochemical Reaction for: Proteus

A

A/A H2S+

urea +, deam +

48
Q

TSI Biochemical Reaction for:

Salmonella

A

K/A H2S+

mal-, ONPG-

49
Q

TSI Biochemical Reaction for:

Shigella

A

K/A

citrate -, non-motile

50
Q

TSI Biochemical Reaction for:

Pseudomonas

A

K/K

ox +, blue-green pigment, growth at 42 degrees C, growth in cetrimide

51
Q

TSI Biochemical Reaction for:

Enterobacter

A

A/A

ODC +, sugars

52
Q

TSI Biochemical Reaction for:

Arizona

A

A/A, H2S+

LDC +

53
Q

TSI Biochemical Reaction for:

Citrobacter

A

K/A or A/A, H2S+

LDC-

54
Q

TSI Biochemical Reaction for:

Providencia

A

K/A

deam +

55
Q

TSI Biochemical Reaction for:

Klebsiella

56
Q

TSI Biochemical Reaction for:

Edwardsiella

A

K/A, H2S+

indole +, LDC +

57
Q

TSI Biochemical Reaction for:

Serratia

A

A/A

sugars

58
Q

TSI Biochemical Reaction for:

Proteus

A

K/A

urea +, deam +

59
Q

TSI Biochemical Reaction for:

Yersinia

A

K/A

small colonies, urea +, deam -

Microbiology (26 decks)

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