Labs 18-21 Flashcards by Apryl Lytle

What is the purpose of MSB

Encourage the growth of staph

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What is the selective ingredient in MSB (m-Staphylococcus Broth) and what does it select for & against?

10% NaCl selects for staph, halophiles; against nonhalophiles

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What is the selective ingredient of MSA and what does it select for & against

7.5% NaCl selects for gram+, staph, and halophiles;

against gram-, nonstaph, & nonhalophiles

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What is the purpose of MSA

Tests for mannitol fermentation, differentiates between staph species

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Explain results of MSA

\+= yellow (d/t acid changing phenol red to yellow)
-= red (did not ferment mannitol)

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What are the differential ingredients of MSA

Mannitol and phenol red

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what is the selective ingredient of SM110 and what does it select for and against

7.5% NaCl selects for gram+, staph, halophiles

Against gram-, nonstaph, & nonhalophiles

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Describe results of SM110

Staph aureus turns golden color; CNS turn white/opaque color

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What is CNS

Coagulase Negative Staph

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What is the purpose of blood agar

Hemolytic patterns used in staph/strep ID

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Results of blood agar

Beta= clear agar
Alpha= green agar
Gamma= no change

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What is the purpose of rabbit plasma

Coagulase test to differentiate staph aureus from CNS

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Results of rabbit plasma

\+= clot formed, solid/semisolid
-= no clot formed, liquid

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Purpose of MHA

Antibiotic sensitivity Kirby-Bauer test; Novobiocin differentiates staph saprophyticus

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Explain results of the Kirby-Bauer test

> 16 mm= S
(means it’s NOT S.saprophyticus)
< 16 mm= R
(Means it IS S. saprophyticus

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What does BHA select for? Purpose of BHA?

Selects for strep; encourages growth of strep/catalase test; differentiates staph vs strep

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Explain results of BHA catalase test

+ bubbles= Staph

- bubbles= Strep

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What is the purpose of the bile esculin slant

Differentiate Gamma hemolytic strep species

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Explain the results of bile esculin slant test

Color change/darkening= + results

- = no color change

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What is the selective ingredient of the salt tolerance broth

6.5% NaCl

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What is the differential ingredient of salt tolerance broth

Glucose & brom cresol purple

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What is brom cresol purple

PH indicator

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What is the purpose of the salt tolerance broth

Differentiate Gamma hemolytic strep species

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Explain the results of the salt tolerant broth

\+ = color change, yellow (acid changing BCP from purple to yellow); turbidity
- = no color change; no turbidity

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Bacitracin used on blood agar differentiated what type of strep species

Beta hemolytic strep species

Explain what A positive beta-hemolytic bacitracin result means

If the zone of inhibition is >10mm then it is positive for (strep pyogenes) group A beta hemolytic strep < 10mm (is negative) means non-group A Streptococcus

Explain what A positive alpha hemolytic optochin result means

>14 mm is positive for Streptococcus pneumoniae | < 14 mm (is negative) means Viridans Streptococcus

What test is used to differentiate staff from strep

Catalase; bubbles = staph; | no bubbles = strep

What test is used to differentiate species of staph

Coagulase test (rabbit plasma)

What test is used to differentiate species of strep

Hemolysis on blood agar

What test is performed on a beta hemolytic strep to differentiate it

Bacitracin test

What test is performed on an alpha hemolytic strep to differentiate it

Optochin test

What test is performed on a gamma hemolytic strep to differentiate it

Bile esculin

If a bile esculin test is positive what test is performed next

6.5% salt tolerance (Salt tolerance broth)

A salt tolerance broth test results & colors

``` += yellow; enterococcus spp - = purple; group D Streptococcus, non-enterococcus ```

Describe the color shape and arrangement of Staphylococcus

Purple, round, irregular clusters; gram + cocci

Describe the color shape and arrangement of Streptococcus

Purple, round, pairs or chains; | Gram + cocci

Staph grow in ____ salt concentrations and what type of oxygen environment

High salt concentration; most are facultative anaerobes

What species of staph is considered to be the most virulent

Staph aureus

What is the most notable virulence factor possessed by Staph aureus

Coagulase production; virtually all strains of staph aureus are coagulase positive

Staph aureus produces what toxin that causes beta hemolysis on blood agar

Alpha toxins produce beta hemolysis

Name of the 2 CNS's we used

S. epidermidis and S. saprophyticus

What 3 things do CNS's NOTproduce

Coagulase, DNase, or alpha toxin

What color will CNS's appear on BA or SM110

Opaque or white

If MSA turns yellow, it is presumed that you isolated ______

S. aureus or S. saprophyticus

What color will S. aureus colonies appear on SM110 agar

Yellow/orange/golden

S. aureus is proven to be coagulase ____ and the other 2 species are ALWAYS coagulase ______

Positive; negative

Coagulase test with rabbit plasma is only valid for ______

Gram + staph like bacteria (some gram - rods can cause false +)

Resistance to novobiocin can be used to presumptively identify _____

S. saprophyticus

The presence of alpha toxin is a definitive characteristic of _______

S. aureus

To be considered susceptible to novobiocin the zone of inhibition on MHA must be greater than

16 mm

Is uv light ionizing or nonionizing

nonionizing

The _____ the wavelength the more damaging it is to cells

Shorter

Uv radiation at _____ nm is the most germicidal

260 nm

When DNA absorbs uv light it causes the formation of _____

Pyrimidine dimers

Pyrimidine dimers form when

A covalent bond is formed between two adjacent T or C molecules in a DNA strand

Define antimicrobials

Compounds that kill or inhibit microorganisms

Define antibiotics

Antimicrobials produced by microorganisms that inhibit or kill other microorganisms

Name 2 common examples of antibiotics

Penicillin and streptomycin

Semi-synthetics

When antibiotics are chemically altered to make them more effective in their mode of action

Synthetics

Antimicrobials that are chemically synthesized; ex: sulfa drugs

example of antibiotics that target cell wall synthesis

Penicillin

example of antibiotics that target DNA and RNA synthesis

Cipro, rifampin

example of antibiotics that target protein synthesis

Tetracyclines, streptomycin

example of antibiotics that target vitamin synthesis

Sulfa drugs

Explain the affect of an outer membrane on the ability of an antibiotic

The outer membrane of gram - bacteria acts as a permeability barrier and can restrict the entry of antimicrobials into the cell

What test is used to determine the sensitivity or resistance of a bacterium to an antimicrobial

Kirby-Bauer method

What media is used for the Kirby-Bauer method

MHA (mueller-hinton agar)

What is measured to determine resistance or sensitivity

Zone of inhibition

Labs 18-21 Flashcards

(69 cards)