micro lab 10-12 Flashcards by Ashley Jones

This bacterium is the #1 most common cause of

food poisoning in our country:

Salmonella

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This bacterium is #2–the second most common

cause of food poisoning in our country:

Campylobacter

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Which G- rod causes a kind of food poisoning

called gastroenteritis?

Salmonella

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Which G- rod causes a condition called

bacillary dysentery?

Shigella

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What ingredients make MacConkey agar selective?

crystal violet and bile salts

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What ingredients make MacConkey agar differential?

lactose and neutral red

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What is the pH indicator used in MacConkey agar?

neutral red

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MacConkey agar results:

growth and pink colonies

Conclusion?

-the bacterium must be G- because it grew

-the bacterium can break down lactose because

of the color change to pink

-the bacterium could be E. coli

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MacConkey agar results:

growth and clear colonies

-the bacterium must be G- because it grew

-the bacterium cannot break down lactose because

there was no color change to pink

-the bacterum could be Salmonella enteritidis

or Pseudomonas aeruginosa

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What is the pH indicator used in TSI agar?

phenol red

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In a TSI slant, how do you read these test results?

Glucose Lactose/Sucrose Gas H2S gas

Glucose: the bottom of the tube turns yellow if the bacteria

can break down glucose.

Lactose/Sucrose: the slant on top turns yellow if the

bacteria can break down lactose and sucrose.

Gas: bubbles and gas pockets are seen if the bacteria

produce a lot of hydrogen gas (H2) and carbon dioxide (CO2).

H2S gas: a black color forms if the bacteria produce

H2S gas.

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TSI slant results for E. coli:

Glucose

Lactose/Sucrose

Gas

H2S

E. coli:

Glucose: +

Lactose/Sucrose: +

Gas: +

H2S: -

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TSI slant results:

bottom of the tube: yellow

slant: yellow

bubbles/gas pockets: yes

black color: no

The G- rod is E. coli.

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TSI slant results for Salmonella enteritidis:

Glucose

Lactose/Sucrose

Gas

H2S

Salmonella enteritidis:

Glucose: +

Lactose/Sucrose: -

Gas: +

H2S: +

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TSI slant results:

bottom of the tube: yellow

slant: red

bubbles/gas pockets: yes

black color: yes

The G- rod is Salmonella enteritidis.

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TSI slant results: Pseudomonas aeruginosa

Glucose

Lactose/Sucrose

Gas

H2S

Pseudomonas aeruginosa:

Glucose: -

Lactose/Sucrose: -

Gas: -

H2S: -

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TSI slant results:

bottom of the tube: red

slant: red

bubbles/gas pockets: no

black color: no

The G- rod is Pseudomonas aeruginosa.

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Tuberculosis: cause

Mycobacterium tuberculosis

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Acid-fast results: from sputum

Bacteria stained red

The patient has tuberculosis.

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Acid-fast results: from sputum

bacteria stained blue

The patient has some type of pneumonia.

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HIV testing: Indirect ELISA

Tests the patient for HIV antibodies in

their serum (plasma).

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HIV testing: Western blot

Tests the patient for HIV epitopes in their blood.

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HIV testing: Oral test

A home kit that is an indirect test. It uses a

swab specimen from the patient’s gums to

test for HIV antibodies.

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HIV testing: Saliva test

A home kit that is an indirect test. It uses

a drop of saliva to test the patient for

HIV antibodies.

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Alpha hemolysis: definition

Incomplete hemolysis; some RBC in the area have been made to burst

Alpha hemolysis: appearance

It appears discolored/greenish on a blood agar plate where the bacteria are growing.

Alpha hemolysis: example

Streptococcus pneumoniae

Beta hemolysis: definition

Complete hemolysis: all RBCs in the area have been made to burst.

Beta hemolysis: appearance

It appears clear on a blood agar plate where the bacteria are growing.

Beta hemolysis: example

Streptococcus pyogenes

Nonhemolytic: definition

The bacteria do no hemolysis at all; no RBCs are made to burst.

Nonhemolytic: appearance

It still appears blood red on a blood agar plate where the bacteria are growing.

Nonhemolytic: example

Enterococcus

Gram stain: Streptococcus pneumoniae

G+ coccus in pairs

Gram stain: Streptococcus pyogenes

G+ coccus in chains

Gram stain: Enterococcus

G+ coccus in chains

Optochin test: clear zone

It is Streptococcus pneumoniae

Optochin test: no clear zone

It is not Streptococcus pneumoniae.

Streptococcus pneumoniae: clinical significance

pneumonia, meningitis, middle ear infections

Bacitracin test: clear zone

It is Streptococcus pyogenes

Bacitracin test: no clear zone

It is not Streptococcus pyogenes.

Streptococcus pyogenes: clinical significance

Strep throat, scarlet fever, Rheumatic fever

Bile esculin test: growth, black

It is Enterococcus.

Bile esculin test: no growth, no black

It is not Enterococcus.

Enterococcus: clinical significance

UTI, Bacterial endocarditis

Mannitol Salt agar: What ingredient(s) make it selective?

Salt (NaCl)

Mannitol Salt agar: What ingredient(s) make it differential?

Mannitol sugar, phenol red

Mannitol Salt agar results: -Growth, stays red

-It must be a Staphylococcus because it grew -It cannot break down mannitol sugar because it did not turn yellow. -It must be Staphylococcus epidermidis.

Mannitol Salt agar results: Growth, turned yellow

-Must be a Staphylococcus because it grew -It can break down mannitol sugar because it did turn yellow. -It could be Staphylococcus aureus or Staphylococcus saprophyticus

Gram stain: Staphylococcus epidermidis, Staphylococcus aureus, Staphylococcus saprophyticus

All species of Staphylococcus are a G+ coccus in clusters.

Staphylococcus epidermidis: Mannitol Salt agar results

-It grows because it is a Staphylococcus -It stays red because it cannot break down Mannitol sugar

Staphylococcus epidermidis: clinical significance

UTI and blood infections

Staphylococcus aureus: Mannitol Salt agar results

-It grows because it is a Staphylococcus -It turns yellow because it can break down mannitol sugar

Staphylococcus aureus: Coagulase

Staphylococcus aureus is the only Staph that produces the enzyme coagulase, which makes plasma clot.

Coagulase test results: plasma clotted

It is Staphylococcus aureus

Coagulase test results: plasma not clotted

It could be Staphylococcus epidermidis or Staphylococcus saprophyticus

Staphylococcus aureus: clinical significance

pimples, boils, skin abscess, food poisoning, pneumonia, blood infections

Staphylococcus saprophyticus: Mannitol Salt agar results

-It grows because it is a Staphylococcus. -It turns yellow because it can break down Mannitol sugar

Novobiocin test: clear zone

It could be Staphylococcus epidermidis or Staphylococcus aureus.

Novobiocin test: no clear zone

It must be Staphylococcus saprophyticus.

Staphylococcus saprophyticus: clinical significance

UTI in females