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Microbiology > Biochemical tests > Flashcards

Biochemical tests Flashcards

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Biology 101 flashcards
1
Q

What is the first test usually used to differentiate gram positive organisms

A

Catalase test –> positive in Micrococcaceae (Staph and Micrococci) and negative in streptococci

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2
Q

Furazolidone susceptibility

A

Used to distinguish susceptible Staph from non-susc Micrococci

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3
Q

What test is used to differentiate S. aureus from other Staph?

A

Coagulase test: coagulase has prothrombin like activity that converts fibrinogen to fibrin

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4
Q

When should the tube coagulase test be performed?

A

When insufficient colonies of Staph is present and the slide test is negative at 30 seconds.

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5
Q

Technique for tube coagulase tube test

A

The tube must be examined at 4 and 20 hours because some strains have fibrinolysin that will dissolve a formed clot and give a false negative if not checked at 4 hours. Others may have a delayed reaction and be negative at 4 hours.

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6
Q

What test is used to distinguish among coagulase negative Staph?

A

Novobiocin susceptibility
Susceptible: S. epidermidis
Resistant: S. saprophyticus

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7
Q

What method is used to differentiate between B-hemolytic streptococci?

A

(A disc) Bacitracin & TMP-SMX susceptibility
Group B strep (agalactiae): Resistant to both
Group A Strep (pyogenes): resistant to TMP-SXT but sensitive to bacitracin
Other B-hemolytic strep: susc to both

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8
Q

What test is used to separate group D enterococci from group D non-enterococci?

A

6.5% NaCl tolerance
Enterococcus spp: salt tolerant
Group D (S. bovis): not salt tolerant

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9
Q

What is the CAMP test?

A

used to identify group B strep by plating it next to staph aureus, B-hemolysin in the staph is enhanced due to the CAMP factor in the GBS
Most other hemolytic strep do not have CAMP factor

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10
Q

What test can replace the bacitracin and salt tolerance tests for identifying Group A and D strep?

A

PYR test

Aminopeptidase produced by these bacteria hydrolyzes PYR which yields a red color

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11
Q

What is the bile esculin test?

A

Used to identify enterococcus and Group D not enterococci (S. bovis), both can grow in bile and hydrolyze esculin–> Diffuse blackening of more than half the slant after streaking and incubating for 24 hrs

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12
Q

How is the optochin disk (P) used?

A

It selectively inhibits S. pneumo

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13
Q

What organism is bile soluble??

A

S. pneumo

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14
Q

What organisms are oxidase negative?

A

Enterobacteriaceae

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15
Q

What organisms are oxidase positive?

A

Vibronaceae, Aeromonas, Neisseria, Pseudomonas, Campylobacter and Pasteurella

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16
Q

What organism is indole + and lactose +?

A

E. coli

17
Q

What organisms reduce nitrate to nitrite?

A

Enterobacteriaceae

18
Q

What is the purpose of Hugh-Leifson OF medium?

A

oxidative-fermentative test is used to determine if gram-negative bacteria metabolize carbohydrates oxidatively, by fermentation, or are nonsacchrolytic and therefore have no ability to use the carbohydrate in the media.

19
Q

How do you interpret Hugh-Leifson OF medium?

A

Yellow= acid production
Yellow only in open tube=oxidative organism
Yellow in both tubes= fermenting organisms
green in both tubes/ blue in open tube=nonsaccharolytic organism

20
Q

What is the string test?

A

Diffferentiates V. cholera because the string becomes more tenacious with time as opposed to others vibrio that have an initial string which diminishes in 60 seconds

21
Q

What organism satellites around a streak of S aueus and why?

A

Haemophilus spp. because of the ability of S aureus to synthesize V factor and to release X factor by lysing blood.

22
Q

Which Haemophilus utilizes only V factor?

A

H parainfluenzae, H parahaemolyticus, H aphrophilus (P’s need the V’s)

23
Q

Which Haemophilus spp utilizes only X factor?

A

H. ducreyi (X-rated transmission)

24
Q

Which Haemophilus spp utilizes X & V factor?

A

H. influenza, H haemolyticus and H aegyptius

25
Q

Which Neisseria spp utilizes only glucose?

A

N. gonorrhae

26
Q

Which Neisseria spp utilizes glucose and maltose?

A

N meningitides

27
Q

Which Neisseria spp utilizes glucose, maltose and sucrose?

A

N sicca

28
Q

Which Neisseria spp utilizes glucose, maltose and lactose?

A

N lactamica

29
Q

Which organism is negative for all sugars on CHO utilization testing?

A

Moraxella catarrhalis

30
Q

What is the superoxol test used for?

A

For the rapid, presumptive diagnosis of N gonorrhea. Superoxol is 30% H202, not the usual 3% used for the catalase test

31
Q

Which gram- coccus produces DNAse?

A

Moraxella catarrhalis

Microbiology (5 decks)

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