Micro Lab Practical

Front 1

Number of viable bacteria per mL calculation

Back 1

Number on plate / mL on plate / Dilution sampled

Front 2

Gram stain steps

Back 2

1) flame slide to warm
2) smear on loopul of broth
3) let air dry
4) pass slide 3-6 time thru flame to fix
5) flood with crystal violet for 60 sec
6) rinse with water for 2-3 sec
7) cover with Gram's iodine for 30-60 sec
8) rinse for 2-3 sec
9) add Gram's decolorizer dropwise for 3-5 sec tiill first flush of purple released
9.5) Rinse IMMEDIATELY
10) Counterstain wit safranin for 45 sec
11) rinse and blot

Front 3

Gram stain steps

Back 3

1) flame slide to warm
2) smear on loopul of broth
3) let air dry
4) pass slide 3-6 time thru flame to fix
5) flood with crystal violet for 60 sec
6) rinse with water for 2-3 sec
7) cover with Gram's iodine for 30-60 sec
8) rinse for 2-3 sec
9) add Gram's decolorizer dropwise for 3-5 sec tiill first flush of purple released
10) Counterstain wit safranin for 45 sec
11) rinse and blot

Front 4

What grows on MacConkey agar

Back 4

Only gram negatives
(gram + can't tolerate the crystal violet)

Front 5

What differential abilities does Macconkey agar have?

Back 5

Lactose fermenters (gram neg) are pink;
Non lactose fermenting gram negs are clear

Front 6

What does manitol salt agar select for and differentiate for?

Back 6

the salt inhibits all BUT Staphylococcus sp.

It differentiates among Mannitol fermenters: mannitol fermenters (including most s. aureus strains) turn phenol red indicator yellow when pH drops.

Front 7

What does red/yellow TSI mean?

Back 7

K/A

Means it is a non-lactose fermenter (that can ferment glucose)

Front 8

What does yellow/yellow TSI mean?

Back 8

A/A

Ferments lactose and/or sucrose

Front 9

Red over red/red-orange TSI

Back 9

No carb fermentation

Front 10

Black

Back 10

H2S pos

Front 11

Kirby-bauer technique

Back 11

1) streak lawn onto Mueller-Hinton agar plate
2) place disc on agar
3) measure diameter of zone of inhibition
4) if zone is greater in area then the intermediate diameter, it is sensitive. If less, it is resistant. Otherwise, intermediate.

Front 12

Lac + aerobe from stool?

Back 12

E. Coli
Enterobacter
Citrobacter

Front 13

Lac neg aerobe from stool?

Back 13

Salmonella
Shigella
Proteus

Front 14

Anaerobes at 35

Back 14

NOT Clostridium

Bacteroides fragilis

Front 15

What does acid fast staining stain?

Back 15

Mycobacterium sp., due to unique cell wall

Mycobacterium stains red, all others stain blue

Front 16

Kinds of hemolysis

Back 16

1) alpha: partial zone, greenish
2) beta: complete hemolysis
3) gamma: no hemolysis

Front 17

What grows on horse blood but not sheep blood? Why?

Back 17

Haemophilus species.

Haemophilus need NAD, which is on horse but not sheep

Front 18

What blood does haemophilus grow on? Why?

Back 18

Horse, not Sheep

It needs NAD, and sheep doesnt have it.

Front 19

when would you use catalase test on gram positive cocci

Back 19

Always: this is the first differentiator

Front 20

When would you use coagulase test on a gram positive cocci?

Back 20

Only if catalase postive (not appropriate for catalase neg)

Front 21

Describe satelliting

Back 21

Though Sheep blood doesnt have the NAD (Factor 5) that Haemophilus sp. needs, it can grow close to s. auerus on sheep blood, as s. auerus makes NAD.

Front 22

What does caogulase test look like?

Back 22

1) make suspension of colony in a drop of plasma
2) If positive, plasma is granular, no homogenous suspenion possible
3) if neg: plasma uniformly turbid/homogenous suspension

Front 23

Oxidase test description

Back 23

(differentiates among some gram negs:)

1) moisten filter paper with oxidase reagent
2) apply colony
3) if psotive, turns paper purpole in 10 seconds

Front 24

Bile escuelin result

Back 24

if positive, slant turns black

Front 25

Optochin sensitivity

Back 25

(P disc)

Pos if inhibition less than 15 mm

Front 26

A disc test

Back 26

(bacitracin)

Front 27

Citrate slant results

Back 27

Pos: growth on slant, green slant turns blue

Front 28

DNAse test

Back 28

Positive=pink zone around growth
Neg=dark blue plate

Front 29

LDC test

Back 29

Neg: broth is bright yellow
Pos: any purple or faded yellow purp

Front 30

Why is s. auerus yellow on manitol salt?

Back 30

S. aureus ferments mannitol, and drop in pH causes phenol red indicator in medium to turn yellow

Front 31

What specimens do you use acid fast on?

Back 31

1) sputum in early morning
2) gastric lavage
3) urine (mid stream in mornin)
4) tissue, CSF, other fluid

Front 32

Anaerobe from stool that grows at 48C

Back 32

Clostridium sp