Microbiology Lab Final Exam, UTC -
Barbosa
What are fastidious organisms? - ✔️✔️any organism that has a complex nutritional
requirement, and will only grow when specific nutrients are included in its diet
How is the blood agar selective? - ✔️✔️The sheep's blood provided the growth factors
for fastidious pathogens
How is the blood agar differential? - ✔️✔️based on the bacteria's ability to cause
hemolysis of blood cells
How is the MSA test selective, and what type of bacteria growth does it NOT inhibit
(allows to grow)? - ✔️✔️It contains mannitol (sugar) which is used for fermentation
The high salt concentration inhibits the growth of most bacteria other than staphylococci
How is the MSA test differential? - ✔️✔️the phenol red is a pH indicator that changes
from red to yellow when the bacteria ferments the mannitol and produces an acid
On the MSA test, which bacteria shows growth AND produces a color change? -
✔️✔️Staphylococcus aureus
On the MSA test, which bacteria produces colonies but does NOT produce a color
change? - ✔️✔️Staphylococcus epidermis
What does MSA stand for? - ✔️✔️Mannitol Salt Agar
What does MAC stand for? - ✔️✔️MacConkey's Agar
What does EMB stand for? - ✔️✔️Eosin Methylene Blue Agar
How is the MAC test selective, and which type of bacteria does it inhibit growth? -
✔️✔️The crystal violet and bile salts inhibit the growth of gram-Positive organisms
The lactose in the agar allows for fermentation
How is the MAC test differential? - ✔️✔️The lactose allows for fermentation, whose
acid end-products act on bile salts, and neutral red is absorbed by the precipitated salts.
Non-fermenting bacteria give an alkaline reaction and are non colored/transparent.
, On the MAC test, which bacteria produced red/pink colonies? - ✔️✔️Escherichia coli
On the MAC test, which bacteria produced colorless colonies? - ✔️✔️Salmonella
enteritidis
How is the EMB test selective? - ✔️✔️The methylene blue acts as an inhibitor to gram-
Positive organisms.
Both lactose and saccharose are included to allow for fermentation.
How is the EMB test differential? - ✔️✔️INDICATOR for those that ferment lactose and
those that do not... eosin & methylene blue
Strong lactose fermentation = green metallic sheen
Weak lactose fermentation/ prefer saccharose = pinkish colonies, mucoid, larger
colonies
No fermentation = colorless
What is hemolysis? - ✔️✔️the destruction of erythrocytes (red blood cells)
What is beta hemolysis? - ✔️✔️The complete breakdown of red blood cells
recognized by a complete zone of clearing surrounding the colony
What is alpha hemolysis? - ✔️✔️Partial destruction of the red blood cells
produces a zone of partial clearing (greenish brown)
What is gamma hemolysis? - ✔️✔️No damage to red blood cells
no change in the medium
Which bacteria showed beta hemolysis? - ✔️✔️Streptococcus pyogenes
Which bacteria showed alpha hemolysis? - ✔️✔️Streptococcus pneumoniae
Which bacteria showed gamma hemolysis? - ✔️✔️Staphylococcus epidermis
Cidal - ✔️✔️a procedure which leads to the death of cells
ex: canning food
Barbosa
What are fastidious organisms? - ✔️✔️any organism that has a complex nutritional
requirement, and will only grow when specific nutrients are included in its diet
How is the blood agar selective? - ✔️✔️The sheep's blood provided the growth factors
for fastidious pathogens
How is the blood agar differential? - ✔️✔️based on the bacteria's ability to cause
hemolysis of blood cells
How is the MSA test selective, and what type of bacteria growth does it NOT inhibit
(allows to grow)? - ✔️✔️It contains mannitol (sugar) which is used for fermentation
The high salt concentration inhibits the growth of most bacteria other than staphylococci
How is the MSA test differential? - ✔️✔️the phenol red is a pH indicator that changes
from red to yellow when the bacteria ferments the mannitol and produces an acid
On the MSA test, which bacteria shows growth AND produces a color change? -
✔️✔️Staphylococcus aureus
On the MSA test, which bacteria produces colonies but does NOT produce a color
change? - ✔️✔️Staphylococcus epidermis
What does MSA stand for? - ✔️✔️Mannitol Salt Agar
What does MAC stand for? - ✔️✔️MacConkey's Agar
What does EMB stand for? - ✔️✔️Eosin Methylene Blue Agar
How is the MAC test selective, and which type of bacteria does it inhibit growth? -
✔️✔️The crystal violet and bile salts inhibit the growth of gram-Positive organisms
The lactose in the agar allows for fermentation
How is the MAC test differential? - ✔️✔️The lactose allows for fermentation, whose
acid end-products act on bile salts, and neutral red is absorbed by the precipitated salts.
Non-fermenting bacteria give an alkaline reaction and are non colored/transparent.
, On the MAC test, which bacteria produced red/pink colonies? - ✔️✔️Escherichia coli
On the MAC test, which bacteria produced colorless colonies? - ✔️✔️Salmonella
enteritidis
How is the EMB test selective? - ✔️✔️The methylene blue acts as an inhibitor to gram-
Positive organisms.
Both lactose and saccharose are included to allow for fermentation.
How is the EMB test differential? - ✔️✔️INDICATOR for those that ferment lactose and
those that do not... eosin & methylene blue
Strong lactose fermentation = green metallic sheen
Weak lactose fermentation/ prefer saccharose = pinkish colonies, mucoid, larger
colonies
No fermentation = colorless
What is hemolysis? - ✔️✔️the destruction of erythrocytes (red blood cells)
What is beta hemolysis? - ✔️✔️The complete breakdown of red blood cells
recognized by a complete zone of clearing surrounding the colony
What is alpha hemolysis? - ✔️✔️Partial destruction of the red blood cells
produces a zone of partial clearing (greenish brown)
What is gamma hemolysis? - ✔️✔️No damage to red blood cells
no change in the medium
Which bacteria showed beta hemolysis? - ✔️✔️Streptococcus pyogenes
Which bacteria showed alpha hemolysis? - ✔️✔️Streptococcus pneumoniae
Which bacteria showed gamma hemolysis? - ✔️✔️Staphylococcus epidermis
Cidal - ✔️✔️a procedure which leads to the death of cells
ex: canning food
