Microbiology practical 3

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Dr. Raymond Mesa Community College

Aspergillus niger. Macroscope

What is this?

Aspergillus niger. Microscope

What is this?

Penicillium. Macroscope

What is this?

Penicillium. Microscope

What is this?

Rhizopus. Macroscope

What is this?

Rhizopus. Microscope

What is this?

Saccharomyces cerevisiae (yeast) macroscope

What is this?

Saccharomyces cerevisiae (yeast) Microscope

What is this?

It grows on yeast or mold depending on the enviornment.

Explain why Coccidiodes immitis is considered to be a dimorphic fungus?

Vegetative hyphae: It grows down or into agar
Areal hyphae: Grows above surface of agar

Explain the difference between vegetative hyphae and arial hyphae

Asexual spores produced at the end of arial hyphae in a sac like structure

Describe a sporangiospore

Formed on hyphae, can be one celled or multi-celled.

Describe a condiospore

Viruses that infect bacteria

Define bacteriophage

Virus' that burst open their bacterial host once the appropriate amount of viruses have been made then killing its host, the bacteria

Define lytic

On a streak plate where bacteria used to be there will be "empty" spots, this is where the virus landed, infected, and lysed the bacteria

Define plaque

To get a countable plaque number of around 30

Explain the the purpose of making dilutions of the T4 virus'

44 x 10^-8 x 10^-1 =
10^9
44 X 10= 4.4x10^10 PFU/ml
plaque dilution sample
count factor amount

Calculate the titer of phage in the original sample given the number of plaques and the dilution of the plate.
44 x 10-8 x 10-1 =
plaque __ dilution sample __ count factor amount=

Organisms that grow only inside another living host

Define obligate intra-cellular parasite

Bacteria: Regular agar broth media
Bacteriophage: Host cell, no media

How does the media used for bacterial growth differ from media used for bacteriophage growth?

Catalase reagent: hydrogen peroxide, it bubbles/no bubble
Coagulase: Rabbit plasma, it clumps or doesn't clump

Explain the principle state and reagent/media used in the catalase and coagulase test

Using the coagulas test, Staphylococcus aureus is positive. Staphylococcus epidermidis is negative. The "S" in Staphylococcus needs to me capitalized and the "e" in epidermidis and the "a" in aureus needs to be lower case. The whole thing should be underlined. You need to know the correct spelling for both.

Requires pen and paper Differentiate the 2 species of Staphylococcus by the coagulate test and who's positive and negative. When writing answer, what rules need to be followed?

(+)

Is Staphylococcus (+) or (-) using the catalase test?

(-)

Is Streptococcus (+) or (-) using the catalase test?

Staphylococcus aureus is yellow meaning it's (+) for mannitol fermentation
Staphylococcus epidermidis (-) is pink or red

Differentiate the 2 species of Staphylococcus by the reaction on the Mannitol salt agar?

It is selective because organisms that grow best in high salt concentrations grow here. It is differential for different species of Staphylococcus.

Explain how Mannitol salt agar is both a selective and differential media.

Micrococcus roseus is rose colored.
Micrococcus luteus is yellow colored.

Determine the species of Micrococcus by the pigmentation test.

Micrococcus roseus is (+)
Micrococcus luteus is (-)

Determine the species of Micrococcus by the nitrate test.

Gram (+) cocci in clusters

Are Staphylococcus and Micrococcus gram (+) or gram (-)? Are they in singles, pairs, chains, or clusters?

On the skin and mucus membrane

Where are Staphylococcus and Micrococcus normally found on the body?

Something that carries a pathogen but exhibits no symptoms

Define carrier

A pathogen resistant to penicillin derivatives such as methicillin and oxacillin

Define MRSA

A hospital acquired infection

Define nosocomial

When an opportunistic host presents its self

When do Staphylococcus epidermidis and Micrococcus cause disease?

Alpha. Greenish brown halos around isolated colonies

What type of hemolysis of an organism is growing on this blood agar?

Beta. You can see through the plate

What type of hemolysis of an organism is growing on this blood agar?

Gamma. White bacteria growing on red plate

What type of hemolysis of an organism is growing on this blood agar?

You "stab" to see hemolysis better

Explain why you use the streak stab method for blood agar inoculations

In a candle jar because its a Microaerophile

State the atmosphere used to grow streptococcus

Larger, raised, opaque, frequently pigmented

Describe the colony appearance of Staphylococcus

Translucent to semi opaque

Describe the colony appearance of Streptococcus

Catalyze

Which enzyme helps differentiate staphylococci from streptococci

It's based on the C polysaccharide extracted from the cell walls

How did Lancefield devide the beta-hemolyic streptococci into groups?

Streptococci pyogenes

What is the species name of Lancefield Group A streptococci?

Streptococci agalactiae

What is the species name of Lancefield Group B streptococci?

GI tract

Where are Enterococcus normally found in the human body?

Vancomycin resistant enterocccus

Define VRE

Alpha hemolytic streptococci other than Streptococci pneumonia

Define viridans streptococci

Strep throat

Group A Strep causes what disease?

Neonatal septicemia (An infant blood infection)

Group B Strep causes what disease?

Urinary tract infection

Enterococcus causes what disease?

Community-acquired pneumonia

Streptococcus pneumoniae causes what disease?

Dental cavities

viridans streptococci causes what disease?

CNA grows grows only gram (+) organisms and MacConkey only grows gram (-) organisms

Explain how CNA and MacConkey agar aid in the identification of bacteria in a mixed unknown

Lactose

What ingredient in the MacConkey agar will differentiate the organisms growing in the agar?

Crystal violet and bile salts

How does the CNA medium prevent the growth of gram (-) rods?

Blood

What ingredient in the CNA media allows differentiation of the organisms growing in the agar?

Streptococcus are microaerophilic

Why is CNA media incubated in a candle jar?

It's a neutral media that all bacteria will grow on

Why is T. soy agar used to grow "stock cultures"?

Staphylococcus aureus

Unknown: Coagulase test, clumps

Staphylococcus epidermidis

Unknown: Coagulase test, no clumps

Staphylococcus aureus positive

Unknown: Mannitol salt agar, negative or positive test result?

Staphylococcus epidermidis negative

Unknown: Mannitol salt agar (quadrant 1 and 2) Positive or negative test result?

Micrococcus roseus

Unknown: Pigment Production (colony color)

Micrococcus luteus

Unknown: Pigment Production (colony color)

Micrococcus roseus positive

Nitrate reduction- turns red with alpha-napththylamine and sulfuric acid. Is this a positive or negative tests result?

Micrococcus luteus negative

Nitrate reduction- Turns red after zinc
Is this a positive or negative tests result?

Alpha Streptococcus mitis and Streptococcus pneumoniae

Unknown hemolysis to detemine bacteria

Streptococcus mitis

Unknown optochin sensitivity test.

Streptococcus pneumoniae

Unknown optochin sensitivity test.

Beta Streptococcus pyogenes and Group C Streptococcus.

Unknown hemolysis test to determine bacteria

Group C Streptococcus

Unknown bacitracin sensitivity test

Streptococcus pyogenes

Unknown bacitracin sensitivity test.

Enterococcus faecalis

Unknown bile esculin test (tube on the right)

Micrococcus luteus positive

Nitrate reduction- No red color after zinc
Is this a positive or negative tests result?

Gram (+)

Does CNA grows gram (+) or Gram (-) ?

Gram (-)

Does MacConkey grow gram (+) or Gram (-) ?

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