Lab #14 Flashcards by Isabel Diaz

Q

Indole Production Test

Add Kovac’s reagent, gently shake, but keep reagent on top of broth

Pink ring indicates

a) Positive
b) Negative

A

a) Positive

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Q

Indole Production Test

Add Kovac’s reagent, gently shake, but keep reagent on top of broth

Yellow ring indicates

a) Positive
b) Negative

A

b) Negative

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Q

Indole Production Test

Pink ring in broth

A

= positive

= has Trp-ase

E. coli vs. other enteric bacteria
Proteus mirabilis vs. other Proteus spp.

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Q

Indole Production Test

Yellow ring in broth

A

= negative

= does not have Trp-ase

E. coli vs. other enteric bacteria
Proteus mirabilis vs. other Proteus spp.

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Q

Methyl Red Test

Add methyl red growth culture; gently shake

Red indicates

a) Positive
b) Negative

A

a) Positive

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Q

Methyl Red Test

Add methyl red growth culture; gently shake

Yellow indicates

a) Positive
b) Negative

A

b) Negative

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Q

Methyl Red Test

Red

A

= positive

= pH < 5

= presence of acids

= has FHase

Klebsiella spp./Enterobacter aerogenes (-) vs. E. coli (+)

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Q

Methyl Red Test

Yellow

A

= negative

= pH > 6

= no acids produces

= lacks FHase

Klebsiella spp./Enterobacter aerogenes (-) vs. E. coli (+)

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Q

Carbohydrate Fermentation Test

Medium

A

Bromocresol purple (BCP) “carbohydrate” broth

(BCP = color pH indicator)

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Q

Carbohydrate Fermentation Tests

purple → yellow

a) positive
b) negative

A

a) positive

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Q

Carbohydrate Fermentation Tests

still purple…

a) Positive
b) Negative

A

b) Negative

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Q

Carbohydrate Fermentation Tests

Inoculate BCP lactose broth

purple → yellow

A

= positive

= pH change (acidic)

= ferments lactose

All Enterobacteriaceae ferment lactose!

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Q

Carbohydrate Fermentation Tests

Inoculate BCP lactose broth

still purple…

A

= negative

= no pH change

= does not ferment lactose

All Enterobacteriaceae ferment lactose!

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Q

Motility Test

Growth away from stab =

a) motile
b) non-motile

A

a) motile

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Q

Motility Test

Growth at stab =

a) motile
b) non-motile

A

b) non-motile

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Q

Urease Test

Yellow =

a) Urease( - )
b) Urease( + )

A

a) Urease( - )

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Q

Urease Test

Pink =

a) Urease( - )
b) Urease( + )

A

b) Urease( + )

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Q

Control of Microbial Growth

_____ _____ are used for control of microbial growth

A

Chemical agents

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Q

Control of Microbial Growth

Antiseptics are mild enough to be used on skin and living tissue

True

False

Study These Flashcards

A

True

Q

Control of Microbial Growth

Examples of antiseptics are:

Study These Flashcards

A

iodine

hydrogen peroxide

alcohol

Q

Control of Microbial Growth

Disinfectants are toxic for living organisms

True

False

Study These Flashcards

A

True

Q

Control of Microbial Growth

Disinfectants are used on inanimate objects

True

False

Study These Flashcards

A

True

Q

Control of Microbial Growth

Examples of disinfectants

Study These Flashcards

A

chlorine bleach

phenol

formaldehyde

Q

Control of Microbial Growth

Bactericidal: completely _____ bacteria

Study These Flashcards

A

completely kills bacteria

**Control of Microbial Growth** **Bactericidal** substances

## Footnote antiseptics disinfectants

**Control of Microbial Growth** **Bactericidal** processes

autoclaving boiling

**Control of Microbial Growth** **Bacteriostatic:** temporarily _____ further growth of bacteria

**inhibit**

**Control of Microbial Growth** Bacteriostatic substances

**antibiotics** (inhibition of bacterial growth → immune cells kills the remaining cells)

**Control of Microbial Growth** **Bacteriostatic processes**

**refrigeration**

**Antibiotics** Definition of **antibiotic**

Natural antimicrobial agents produced by microbes (e.g. penicillin, from Penicillium notatum—a mold)

**Antibiotics** Antibiotics are safe enough to be ingested **True** or **False**

**True**

**Antibiotics** Antibiotics can be _______ or \_\_\_\_\_\_\_

bacteriostatic or bactericidal

**Antibiotics** **Bacteriostatic antibiotics** at a ____ enough concentration can be **bactericidal**

**high**

**Antibiotics** **Bactericidal antibiotics** at ____ enough concentration can be **bacteriostatic**

**low**

**Antibiotics** Achieve **antimicrobial effect** by one of the following mechanisms: 1. 2. 3. 4. 5.

1. Inhibiting cell wall synthesis 2. Inhibiting protein synthesis 3. Alteration of cell membranes 4. Inhibition of nucleic acid synthesis 5. Interfering with metabolic pathways

**Antibiotics** **Broad spectrum**: effective against a _____ variety of different bacteria \* Neomycin and tetracycline affect both Gm(+) and Gm(-) bacteria a) wide b) particular

**a) wide**

**Antibiotics** **Narrow spectrum**: effective against a _____ group of bacteria \* Rifamycin – tuberculosis-causing bacteria \* Bacitracin(found in Neosporin® )- Gm(+) bacteria only a) wide b) particular

**b) particular**

**Antibiotic Sensitivity Test** Why is it used? What does it help understand? Why do hospitals use them?

Used to estimate effectiveness of known antibiotics vs. certain bacteria Helps in understanding which antibiotic(s) will be most effective in combating bacterium in question Hospitals routinely perform ASTs to decide on the most effective treatment plans

**Kirby-Bauer Method** Also known as the _____ \_\_\_\_\_ _____ of antibiotic sensitivity testing

**disc diffusion method**

**Kirby-Bauer Method** \_\_\_\_\_ _____ soaked with a known amount of antibiotic at _____ \_\_\_\_\_

**Paper discs** **various concentrations**

**Kirby-Bauer Method** Disc on plate → antibiotic diffusion into agar

**diffusion into agar**

**Kirby-Bauer Method** Concentration of antibiotic _____ with distance from disc a) increases b) descreases

**b) decreases**

**Kirby-Bauer Method** Same microbe spread over entire plate If A, B, and C are the **_same antibiotic_** _at_ **_different concentrations_**, then in order of \_\_\_\_\_ a) concentration b) effectiveness

**a) concentration** B \> C \> A

**Kirby-Bauer Method** Same microbe spread over entire plate If A, B, and C are the _**different antibiotics** at the **same concentration**_, then in order of \_\_\_\_\_ a) concentration b) effectiveness

**b) effectiveness** B \> C \> A

**Kirby-Bauer Method** Effectiveness of antibiotic is measured in size of _____ \_\_ \_\_\_\_\_

**ZONE OF INHIBITION**

**Kirby-Bauer Method** Bacterial growth is _____ in the presence of the antibiotic a) inhibited b) allowed

**a) inhibited**

**Zone of Inhibition**