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Introduction to Microbiology > Interpretation of the results from metabolic assays (Lab) > Flashcards

Interpretation of the results from metabolic assays (Lab) Flashcards

1
Q

What does it mean when halos form around the colonies in a starch hydrolysis test?

A

Amylase is produced and the organism is hydrolyzing starch

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2
Q

What does it mean when no halos form around the colonies in a starch hydrolysis test?

A

No amylase is present. No starch hydrolysis

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3
Q

What does it mean when the tube is blue in an oxidative-fermentation test?

A

The organism can’t use glucose and is using the peptone instead, which produces alkaline ammonia

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4
Q

What does it mean when the aerobic tube is yellow, but the anaerobic tube is green in an oxidative-fermentation test?

A

The organism does glucose oxidation only in the presence of O2

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5
Q

What does it mean when the both the aerobic and anaerobic tubes are yellow in an oxidative-fermentation test?

A

The organism does glucose fermentation with or without O2

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6
Q

What does it mean when the tube is yellow in a carbohydrate fermentation test?

A

The organism is fermenting the carbohydrate and producing acid

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7
Q

What does it mean when the tube is red in a carbohydrate fermentation test?

A

The organism is not fermenting the carbohydrate and is using the peptone instead, producing alkaline ammonia

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8
Q

What does it mean when the tube is red on the top and yellow in a carbohydrate fermentation test?

A

The organism was fermenting the carbohydrate, produced a bunch of acid, and used it up, then starting using the peptone in aerobic conditions and created ammonia, which changed the phenol red back to red

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9
Q

What does it mean when the tube is red in a methyl red test?

A

The organism is not producing acid, so it does not do mixed acid fermentation

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10
Q

What does it mean when the tube is yellow in a methyl red test?

A

The organism is doing mixed acid fermentation and is producing large amounts of acid

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11
Q

What does it mean when the tube is red in a Voges-Proskauer test?

A

The organism is doing butanediol fermentation and is producing acetoin

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12
Q

What does it mean when the tube is yellow in a Voges-Proskauer test?

A

The organism is not producing acetoin

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13
Q

What does it mean when the agar is green in a citrate test?

A

The organism can’t use citrate for fermentation, so doesn’t have citrate lyase and can’t grow

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14
Q

What does it mean when the agar is blue in a citrate test?

A

The organism has citrate lyase and can grow using citrate for fermentation

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15
Q

What does it mean when the bacterial smear is stringy in a KOH test?

A

Gram-negative. The membrane got destroyed and the DNA got released

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16
Q

What does it mean when the bacterial smear doesn’t do anything in a KOH test?

A

Gram-positive. The PG layer protected the membrane so the DNA stays in the cell

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17
Q

What does it mean when the test strip turns blue in an oxidase test?

A

Cytochrome C is present and ADMA oxalate got oxidized and turned blue

18
Q

What does it mean when the test strip stays colourless in an oxidase test?

A

Cytochrome C is absent

19
Q

What does it mean when the tube is yellow in an ONPG test?

A

Beta-galactosidase is present and lactose is being broken down

20
Q

What does it mean when the tube is colourless in an ONPG test?

A

No beta-galactosidase and no lactose breakdown

21
Q

What does it mean when the tube is red in an indole test?

A

Tryptophanase is present and indole is being produced

22
Q

What does it mean when the tube is yellow in an indole test?

A

No tryptophanase and no indole

23
Q

What does it mean when colonies are yellow on MacConkey agar?

A

They’re enteric and gram-negative, but don’t do lactose fermentation

24
Q

What does it mean when colonies are pink on MacConkey agar?

A

Enteric and gram-negative and do lactose fermentation (acid caused the dye to be absorbed)

25
Q

What does it mean when colonies are pink with pink haloes on MacConkey agar?

A

Enteric, gram-negative, and strong lactose fermenters that caused the bile salts to precipitate around the colonies

26
Q

What does it mean when the organism doesn’t grow on MacConkey agar?

A

Is gram-positive and can’t tolerate the crystal violet, or is non-enteric

27
Q

What does it mean when colonies are metallic green on EMB agar?

A

Gram-negative and do mixed acid fermentation, which caused the eosin to turn black

28
Q

What does it mean when colonies are fish-eye on EMB agar?

A

Gram-negative and do some sort of fermentation that isn’t mixed acid, so they produce less acid and less eosin turns black

29
Q

What does it mean when colonies are light pink on EMB agar?

A

Gram-negative and don’t do lactose fermentation, but do absorb the eosin

30
Q

What does it mean when the organism doesn’t grow on EMB agar?

A

Gram-positive

31
Q

What does it mean when bubbles are produced in a catalase test?

A

Catalase is present and the organism is part of the Micrococcaceae

32
Q

What does it mean when no bubbles are produced in a catalase test?

A

Catalase is absent and the organism is a Streptococcaceae

33
Q

What does it mean when gas is produced in a nitrate reduction test?

A

Positive for nitrate reduction. The organism is producing NO, N2O, or N2 from reducing nitrate

34
Q

What does it mean when the tube turns red after adding sulfanillic acid and alpha-naphthylamine in a nitrate reduction test?

A

Positive for nitrate reduction. The organism is reducing nitrate to nitrite

35
Q

What does it mean when the tube turns red after adding the zinc in a nitrate reduction test?

A

Negative for nitrate reduction. Nitrate is still present in the tube so the organism isn’t using it

36
Q

What does it mean when the tube turns yellow after adding the zinc in a nitrate reduction test?

A

Positive for nitrate reduction. Nitrate is being reduced to some other byproduct that isn’t detected

37
Q

What does it mean when the agar is discoloured green or brown around the colonies on blood agar?

A

Alpha-hemolysis. The organism produces hemolysins that reduce Hb but don’t lyse red blood cells

38
Q

What does it mean when the agar is cleared around the colonies on blood agar?

A

Beta-hemolysis. The organism produces hemolysins that completely lyse red blood cells

39
Q

What does it mean when the agar isn’t cleared or discoloured around the colonies on blood agar?

A

Gamma-hemolysis. The organism doesn’t produce hemolysins

40
Q

What does it mean when colonies are yellow on mannitol salt agar?

A

The organism can tolerate high salt and ferments mannitol

41
Q

What does it mean when colonies are pink on mannitol salt agar?

A

The organism can tolerate high salts but can’t ferment mannitol

42
Q

What does it mean when the organism doesn’t grow on mannitol salt agar?

A

It can’t tolerate high salt

Introduction to Microbiology (18 decks)

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