Introduction to Microbiology Techniques

Question 1

Known amounts of pure chemical substances, predictable and reproducible, ideal for all media

Answer 1

Defined media

Question 2

Nonselective, nutrient media, supports large number of organisms (ex. TSA, SBA)

Answer 2

Primary (nonselective) isolation media

Question 3

Contains inhibitors to retard some organisms (ex. MAC, HEK, XLD)

Answer 3

Selective isolation media

Question 4

Indicators allow recognition of certain biochemical reactions (ex. MAC; those that utilize lactose and those that don’t)

Answer 4

Differential media

Question 5

Promotes growth of some organisms, contains enrichments (ex. CHOC, often incubated in CO2 incubator for growth of fastidious organisms)

Answer 5

Enrichment media

Question 6

Allows survival of organisms for extended periods, limits sugars (or adds extra buffer to counteract acids in sugar fermentation) and avoids selective agents

Answer 6

Maintenance media

Question 7

Inhibits growth of unwanted organisms (usual flora), only used in selective media, mostly used in specimens w/ mixed normal flora, selectivity is also concentration dependent

Answer 7

Selective agents

Question 8

Selective agent dye that inhibits GP and fastidious GN

Answer 8

Brillian green

Question 9

Selective agent DYES that inhibit GP

Answer 9

Eosin, methylene blue, basic fuchsin

Question 10

Heavy meatl that inhibits GP and most GN

Answer 10

Bismuth

Question 11

Used for isolation of Salmonella (GN)

Answer 11

Bismuth sulfide agar

Question 12

Dyes, heavy metals, antimicrobials, and other chemicals are used as ____

Answer 12

Selective agents

Question 13

Chemical that inhibits GP, blue

Answer 13

Citrate

Question 14

Chemical that inhibits GP, bile salts

Answer 14

Sodium desoxycholate

Question 15

Chemicals that inhibit GN

Answer 15

Phenylethyl alcohol and azide

Question 16

High concentration of ____ is inhibitory to most organisms (except Staphylococcus)

Answer 16

NaCl

Question 17

This agar is used to isolate Staphylococcus

Answer 17

Mannitol Salt agar (MSA)

Question 18

Binds O2 in anaerobic medium

Answer 18

Reducing agents

Question 19

oxidation-reduction potential in anaerobic medium

Answer 19

Eh indicators

Question 20

Areas w/ flora usually require use of what kind of agar?

Answer 20

Selective and differential

Question 21

This media is often added on specimens from normally sterile areas

Answer 21

Enrichment media

Question 22

Used in most laboratories on ALL routine specimens, best medium for colonial morphology, only medium used for determination of hemolysis

Answer 22

Sheep Blood Agar (SBA)

Question 23

The most frequently used liquid medium for cultivation of organisms from original specimens (swabs, CSF, etc.), enriched will NOT support growth of many fastidious organisms, anaerobes will grow in lower levels in this b/c of less O2 tension

Answer 23

Thioglycollate broth

Question 24

Selective agar, antibiotics inhibit most GN organisms, appearane is similar to SBA

Answer 24

Colistin Nalidixic Acid (CNA) Agar

Question 25

Selective and differential agar, GP organisms INHIBITED (crystal violet and bile salts), used for isolating and differentiating GNRs

Answer 25

MacConkey Agar (MAC)

Question 26

Lactose positive colonies are ____

Answer 26

Dark pink

Question 27

Lactose negative colonies are ____

Answer 27

Very ligth pink

Question 28

Selective and differential agar, GP organisms INHIBITED, used for isolating and differentiating GNRs (lactose and other CHO's), used primarily for isolating pathogens in stool

Answer 28

Xylose, Lysine, Desoxycholate agar (XLD)

Question 29

Color of CHO positive on XLD plate

Answer 29

Yellow

Question 30

Color of CHO negative on XLD plate

Answer 30

Clear/red (color of original medium)

Question 31

Color of H2S-producing organism on XLD plate

Answer 31

Black

Question 32

Selective and differential agar, GP organisms inhibited by bile salts, used for isolating and differentiating GNR's (lactose and other CHOs), used primarily for isolating pathogens in stool

Answer 32

Hektoen Agar (HE or HEK)

Question 33

Color of CHO positive organisms on HE or HEK plate

Answer 33

Orange

Question 34

Color of CHO negative organisms on HE or HEK plate

Answer 34

Clear/green (color of original medium)

Question 35

Color of H2S-producing organisms on HE or HEK plate?

Answer 35

Black

Question 36

Selective and differential agar, inhibits GP organisms, often used for E. coli identification (green sheen)

Answer 36

Eosin Methylene blue (EMB)

Question 37

Enrichment media, no selective agents, supports growth of most organisms and many fastidious organisms, particularly Haemophilus and Neisseria used for spinal fluid

Answer 37

Chocolate agar

Question 38

Selective enrichment agar, chocolate agar w/ antimicrobials, primarily used on genital or rectal specimens for isolation of Neisseria gonorrhoeae or Neisseria meningitidis while inhibiting usual flora

Answer 38

Martin-Lewis, Thayer Martin media

Question 39

Used to disinfect non-metallic surfaces, effective against HIV and HBV(

Answer 39

Sodium hypochlorite (bleach)

Question 40

Autoclave temp, PSI, and time

Answer 40

121C, 15 PSI, 15-20 minutes (not for large volumes)

Question 41

List 3 aerobes

Answer 41

Obligate aerobe, microaerophile, facultative anaerobe

Question 42

List 3 anaerobes

Answer 42

Aerotolerant anaerobes, moderate obligate anaerobes, strict obligate anaerobes

Question 43

Incubation ccondition for ambient air or non-CO2 incubator

Answer 43

21% O2, 0.03% CO2 (room air); aerobic

Question 44

Incubation conditions for CO2 incubator

Answer 44

15% O2, 5-10% CO2 (room air w/ extra CO2 pumped in); aerobic

Question 45

Incubation conditions for microaerophilic incubator

Answer 45

5% O2, 10% CO2; aerobic

Question 46

Incubation conditions for anaerobic incubator

Answer 46

0% O2, 5-10% CO2

Question 47

Where do we put biochemicals, differential media, and antimicrobial susceptibility tests?

Answer 47

Ambient air incubators

Question 48

Where do we put primary plates and fastidious organisms?

Answer 48

CO2 incubators (capnophilic)

Question 49

These provide initial clue to cause of infecction, may dictate therapy decisions, evaluate quality of specimen, tells us if we need additional media, determines if we should QC for culture results

Answer 49

Direct smears

Question 50

Primary stain in Gram stain (add Na Biocarbonate)

Answer 50

Crystal violet

Question 51

Mordant in Gram stain, complexes w/ crystal violet inside cell and makes it difficult to wash out

Answer 51

Iodine

Question 52

Decolorizer in Gram stain

Answer 52

Acetone/Alcohol

Question 53

Counterstin in Gram stain

Answer 53

Safranin

Question 54

Have increased peptidoglycan in cell wall which retains crystal violet and will stain dark blue-purple

Answer 54

Gram positive

Question 55

Have incrased lipid content, dissolved w/ acid/alcohol allowing crystal violet to flow out of cell, stains pink-red

Answer 55

Gram negative

Question 56

Stain useful for high lipis in cell wall where acidified alcohol is used, stains mycobacteria includingM, tuberculosis and related bacteria, Ziehl-Neelsen and Kinyoun Methods, stain red = positive, blue = negative

Answer 56

Acid fast (AF)

Question 57

Stains nucleic acid, fluorescent dye, bacteria stain yellow, used most often in blood smears

Answer 57

Acridine orange

Question 58

These methods can be spot tests, chromogenic or fluorogenic substrates by enzymes, slide agglutinations or ELISA, nucleic and methods, or automated systems

Answer 58

Rapid methods

Question 59

What does MALDI-TOF stand for?

Answer 59

Matrix Assisted Laser Desportion--Time of Flight