Micro 2420 Lab Practical Exam 4

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Differential Medium

Back 1

Used to identify colonies of a particular type of microorganisms from other bacterial colonies growing on same plate

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Thioglycollate Broth (THIO)

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Contains thioglycollate, which reacts to oxygen, allowing cultivation of anaerobic microorganisms in lower part of the tube. Aerobic microbes grow on the surface of the tube and facultative anaerobic will grow throughout the entire tube.

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(THIO)

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anaerobic microorganisms in lower part of the tube. Aerobic microbes grow on the surface of the tube. facultative anaerobic will grow throughout the entire tube.

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Cooked Meat Broth (CM)

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This media allows you to differentialte bacteria that release exo-enzymes, which digest meat.

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Eosin Methylene Blue Agar (EMB)

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This media is selective and differential that contains lactose to aid and identify coliform bacteria,which are gram negative lactose fermenting rods. in addition, it contains eosin and methyl blue, which prevent the growth of gram positive bacteria. Green metallic sheen and a dark purple center are positive colonies.

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MacConkey Salt Agar(MAC)

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This media is selective and differential media for gram positive bacteria (staphylococcus aureus) The media contains high salt concetrations of alcohol mannitl. S. aureus tolerate high salt concentration and has the ability to fermanet mannitol into acid. Yellow colonies are positive for S. Aureus

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Tryptic Soy Agar (TSA)

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This media is used to select psychrotrophic microorganisms that are able to grow at 5 degree Celcius

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Gas Pak Apparatus

Candle Jar Apparatus

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Ancient way to test
Anaerobic Growth

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Physical way by which bacterial is killed?

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By Heat

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Thermal Death Time (TDT)

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Minimal Time Required to kill all microbes in liquid suseptibility by heat.

Front 11

UV Light

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Damages DNA of exposed cells

Front 12

Is used to identify colonies of a particular type of microorganisms from other bacterial colonies growing on the same plate?

Back 12

Differential Media

Front 13

Allows cultivating anaerobic, aerobic and facultative anaerobic microbes.

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Thiglycollate Broth (THIO)

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Thiss media allows you to differentiate bacteria that release exo-enzymes

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Cooked Meat Broth (CM)

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Growth on this media as green metallic sheen colonies or dark purple center colonies, which are positive for coliform bacteria such as E. coli.

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Eosin Methylene Blue Agar (EMB)

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This media contains bile salts and crystal violet, which prevent the growth of gram positive bacteria. Positive bacteria appear as red or pink colonies.

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MacConkey Agar (MAC)

Front 17

this media is a selective and differential media for gram positive bacteria such as staphylococcus aureus

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Mannitol Salt Agar(MAN)

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this media is used to select psychrotrophic microorganism abe to grow at 5C

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Tryptic Soy Agar (TSA)

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is a differential media used to identify gram positive coccus such as Streptococcus Pyogenes. Clear zone around the colonies are positive for Beta red cell hemolysis.

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Blood Agar(BA)

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is defined as the minimal time required to kill all microorganisms in liquid at a given temperature.

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Thermal Death Time (TDT)

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damages the chromosomal DNA of exposed cells leading to thymidine dimer formation.

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Ultraviolet Light (UV)

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What plate is used to culture your throat,nose?

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(BA) Blood Agar- throat
(MAN) Mannitol Salt Agar-Nose

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Oxygen Requirements:

THIO

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A=Aerobe
F=Facultative
AN=Anaerobe

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Oxygen Requirements:

CM

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Fuzzy edges on all meat =
+ digestion
Sharp edges on all meat =
- digestion

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Oxygen Requirements:

EMB

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Purple under colonies =
+coliforms (E.coli is metallic green on top)

No purple under colonies =
- Coliforms

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Oxygen Requirements:

MAC

Both EMB and MAC inhibit G+ microbes

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Pink or red under colonies =
+coliforms (E.coli turns plate bright pink)

No pink or red under colonies=
- coliforms

coliforms = G (-) lactose fermenting rods

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Oxygen Requirements:

BA

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Clear Zone (no RBC's) =
B (Beta Hemolysis)
Partial clearing, green tinge= A(alpha hemolysis)
No clearing = G(gamma Hemolysis)

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Oxygen Requirements:

TSA Slant = 5C

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Visible colony = +growth
No visible colony = -growth

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Oxygen Requirements:

NB tubes

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cloudy = +growth
clear = -growth

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UV Plates

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3/4 growth on UV side = +++
1/2 growth on UV side = ++
1/4 growth on UV side = +
No growth on UV side = -

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Observation of
"Differential Media"
THIO

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A= Fuzzy on top
F= Fuzzy through tube
AN= Fuzzy bottom like u shape

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Observation of
"Differential Media"
CM

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White growth on bottom = +
Crystals at bottom = -

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Observations
"Temerature Effects"
TSA - 5c

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growth in bubble = +
no growth in bubble = -
(teacher said effects of temp will always be +)

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Observations
"Temerature Effects"
NB

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Growth through out tube = +
no growth through out = -
(teacher said effects of temp will always be +)

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Obserevations
"Uv effects"

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Control/UV Petri dishes
unbroken streak UV sec= +++
partial streak ++ or +
no streak uv sec = -

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Antiseptics

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Used on living surfaces

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Disinfectants

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used on non living or inanimate objects/surfaces

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paper disk method

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The effectiveness of a chemical agent (antiseptic or disinfectant) against specific microorganisms is determined by this method.

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Drugs used to treat disease are called chemotherapeutic agents, and scientific chemotherapetuic agents used to treat infections are called?

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Antimicrobial agents

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Antibiotics

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are metabolic products of one microorganism that kill or inhibit the growth of other microbes.

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Antibiotic sensitivity / susceptibility tests

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disc diffusion method-
Kirby-Bauer Method (uses filter paper discs)

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Kirby-bauer Method
"method used to test sensitivity of antibiotics"

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paper discs are impregnated w/ known quantities of antimibrobial agents.
A petri dish known as the Mueller Hinton Agar (MHA), is inoculated with the microbe to be tested.

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antibiotic disc surrounded by clear Halo is

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Zone of inhibiiton

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In Zone of inhibition low drug concentration(ie farther from the disc) the ZOI is what?

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Large

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If ZOI growth is inhibited only by a high drug concentration, the zone will be?

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Small

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ZOI is measured in?

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MM-millimeters from the edge of paper disc to the CLOSEST colongy of growth count in 10s

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based on measurement in ZOI-
S-sensitive
I-Intermediate
R-resistant

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S-highly susceptible
I-ok drug not the best
R- Resistant to that drug

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paper disk method can be used on what dish for antiseptics and disinfectants?

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NA - nutrient agar

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antibiotic ointments and other microbial agents with the paper disk method and the Kirby bauer test were performed on?

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Mueller Hinton Agar(MHA)
this will determine the effect of antibiotics on the microbes.

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0-11 is Resistant
12-14 Intermediate
15+ Sensitive

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Ruler in MM
1- 10mm
2- 20mm etc....

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food bacteria
Lactobacillus and some strains of streptococcus ferment sugars into lactic acid

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not harmful and found in acidophilus milk, butter, sour cream, yogurt and cheeses

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vinegar

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also a product of a bacterium, acetobacter.
produced by yeast, saccharomyces

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MSA

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Mitiss salivarius Agar

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TJA

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Tomato juice Agar

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THB

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Todd Hewitt Broth

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MSA, TJA and THB
are used for?

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To demonstrate the presence of lactic acid bacteria streptococcus and lactobacillus

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microfilm vinegar

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Acetobacter

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Cheese

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Lactobacillus

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Sour Milk

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lactobacillus bacteria

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Caries Susceptibility Test
(use snyder test agar add saliva bromcresol green turns yellow if +)incubate 48hrs@37degrees

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Dental caries-Cavities due to damage of tooth enamel
due to streptococcus mutans

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MSA plate observations
Blue colonies= +streptococcus
no blue= - streptococcus
(Blue plate)

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need to add 1 drop h202 to blue colonies
no bubbling- +strept(catalase -)
bubbling= -strept (catalase+)

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THB observations
cloudy, white growth= +strept
Clear, no white growth = -stre

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TJA observations
White colonies = +lactobacillus

no white colonies=
-lactobacillus

Front 63

pipetting-TD
Mouth top,Body has #'s and tip
TD=delivers @20 degrees

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TD or to deliver
means last drop of sample must be blown out of the pipette in order to measure correctly.

Front 64

Pipetting by mouth is prohibited. It must be done with a what?

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Propipette bulb

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In U.S.coliform bacteria, defined as gram- facultative anaerobic, nonspore-forming, rod shaped bacteria, ferment lactose with acid/gas formation w/in 48hrs at 37C are used as what?

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Indicators for how free our water is of contaminates.

Front 66

MPN stands for what?

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Most probable number
which represents the most probable number of coliforms/100ml of water sample. tube incubated for 48hrs

Front 67

the test is positive if acid and gas are produced then, approximate number of coliforms can be calculated using what?

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MPN table
ex 3 1 1 = 75 according to table

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To confirm that the gas producing organisms are coliforms, a sample from the test water is plated on what?

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EMB-
Eosin Methylene Blue Agar.
if the cultured bacteria produce colonies with a green metallic sheen and purple centers, the confirmed test is positive for coliforms.

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In order for milk to be classified as Grade A by USDA standards what must happen?

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Bacterial numbers must not exceed 20,000 bacteria/ml of milk and 10 coliforms/ml

Front 70

to count the colonies would be impossible so therefore what method is used?

Back 70

serial dilutions

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Visible colonies following 48 hr incubation and counted using what method

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Stadard plate count(SPC), multiplied with the dilution of the number of bacteria/ml present in original sample.

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DSL

SSL

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Double strength Lactose

Single strength lactose

Front 73

Water test:
yellow, gas = +
Pink or red = -
yellow no gas = -

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purple colonies on EMB = -

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Milk Test:
bacteria/ml = SPC x Dilution

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Optional Note:
EMB plates are red/maroon in color