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32 Cards in this Set

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Number of viable bacteria per mL calculation
Number on plate / mL on plate / Dilution sampled
Gram stain steps
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
Gram stain steps
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
What grows on MacConkey agar
Only gram negatives
(gram + can't tolerate the crystal violet)
What differential abilities does Macconkey agar have?
Lactose fermenters (gram neg) are pink;
Non lactose fermenting gram negs are clear
What does manitol salt agar select for and differentiate for?
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.
What does red/yellow TSI mean?
K/A

Means it is a non-lactose fermenter (that can ferment glucose)
What does yellow/yellow TSI mean?
A/A

Ferments lactose and/or sucrose
Red over red/red-orange TSI
No carb fermentation
Black
H2S pos
Kirby-bauer technique
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.
Lac + aerobe from stool?
E. Coli
Enterobacter
Citrobacter
Lac neg aerobe from stool?
Salmonella
Shigella
Proteus
Anaerobes at 35
NOT Clostridium

Bacteroides fragilis
What does acid fast staining stain?
Mycobacterium sp., due to unique cell wall

Mycobacterium stains red, all others stain blue
Kinds of hemolysis
1) alpha: partial zone, greenish
2) beta: complete hemolysis
3) gamma: no hemolysis
What grows on horse blood but not sheep blood? Why?
Haemophilus species.

Haemophilus need NAD, which is on horse but not sheep
What blood does haemophilus grow on? Why?
Horse, not Sheep

It needs NAD, and sheep doesnt have it.
when would you use catalase test on gram positive cocci
Always: this is the first differentiator
When would you use coagulase test on a gram positive cocci?
Only if catalase postive (not appropriate for catalase neg)
Describe satelliting
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.
What does caogulase test look like?
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
Oxidase test description
(differentiates among some gram negs:)

1) moisten filter paper with oxidase reagent
2) apply colony
3) if psotive, turns paper purpole in 10 seconds
Bile escuelin result
if positive, slant turns black
Optochin sensitivity
(P disc)

Pos if inhibition less than 15 mm
A disc test
(bacitracin)
Citrate slant results
Pos: growth on slant, green slant turns blue
DNAse test
Positive=pink zone around growth
Neg=dark blue plate
LDC test
Neg: broth is bright yellow
Pos: any purple or faded yellow purp
Why is s. auerus yellow on manitol salt?
S. aureus ferments mannitol, and drop in pH causes phenol red indicator in medium to turn yellow
What specimens do you use acid fast on?
1) sputum in early morning
2) gastric lavage
3) urine (mid stream in mornin)
4) tissue, CSF, other fluid
Anaerobe from stool that grows at 48C
Clostridium sp