NURS 5338 PRACTICE EXAM TIPS QUESTIONS AND
ANSWERS GRADED A+
✔✔What colors would you expect to see on an EMB plate containing E. coli? - ✔✔The
EMB plate itself is red in color while in the presence of E coli, the growing colonies will
take on a distinctive metallic green sheen.
✔✔While observing an unknown sample of limited amounts, a researcher must
determine the
following observations: (1) the presence of any motility and (2) its Gram status using the
same
sample—the liquid sample cannot be divided. Which would you determine first and
why? - ✔✔You must determine motility before determining the Gram status. Motility
requires a wet
mount, while Gram staining requires heat fixing the sample. If one were to begin with
the
Gram stain the heat fixation process would kill the organism, making any observations
regarding motility impossible. The correct approach would be to place the liquid culture
on a
glass slide and determine its motility status. Next, the same liquid culture can be heat
fixed
and Gram stained
✔✔What is the name of the process of spreading a bacterial culture onto a petri dish? -
✔✔Plating. Plating microbes can be done using a sterile loop, a sterile swab, or a
sterilized wire loop. Each device is simply a means of spreading the bacteria, most
commonly in a simple back-and-forth motion, across the plate.
✔✔What is the primary advantage of plating a bacterial culture as opposed to having it
grow in solution? - ✔✔The primary advantage of plating a bacterial sample onto agar is
that cells are held in place. Unlike in a nutrient broth where bacterial cells can multiply
but are free to move around in solution, bacteria plated onto agar are fixed in such a
way as to support the formation and visualization of colonies.
✔✔A researcher is studying a strain of E. coli currently growing on a MacConkey plate.
However, the researcher can't remember if E. coli is Gram-Positive or Gram-Negative.
Would a Gram stain be necessary to confirm? Why or why not? - ✔✔No. A Gram stain
would
not be necessary, as only Gram- Negative microbes will grow on MacConkey agar.
Thus, E.
coli is a Gram-Negative microbe
✔✔What is the purpose of the quadrant streak approach? - ✔✔The purpose of this
method is to generate an individual colony so that a single (pure) bacterial sample can
be picked from the plate.
,✔✔A facultative anaerobe is a microorganism capable of growth under what conditions?
- ✔✔A facultative anaerobe is capable of growth under aerobic (with oxygen) and
anaerobic
(without oxygen) conditions.
✔✔In a three-phase dilution gradient, which phase most likely contains individual
colonies: phase 1 (P1) or phase 3 (P3)? - ✔✔Individual colonies are most likely going to
appear within the phase 3 streaks. You begin with P1 (highest concentration), dilute
during P2 and then further dilute the sample in P3. However, it is possible to see
individual colonies in P2 if only a small portion of P1 was carried over into P2.
✔✔True or False: Differential media is best suited for distinguishing between two similar
species of bacteria. - ✔✔True
Growth media does not contain restrictive factors, while selective media is best used to
encourage the growth of one microbe while simultaneously discouraging the growth of
the other. Since two similar species of microbes are being studied they must be
differentiated under similar but just slightly different conditions (differential media).
✔✔True or False: Chocolate (cocoa) is not a component of Chocolate agar plates. -
✔✔True, The name is derived simply based on the color that actually comes from the
presence of 'cooked' (lysed) red blood cells in the media.
✔✔In an attempt to detect the presence of the pathogenic strain of E. coli O157:H7, a
researcher spread a culture onto a MacConkey agar with failed results. What type of
agar should they (correctly) try next? Why? - ✔✔The microbe should be plated on
SMAC
(Sorbitol-MacConkey agar) as it is specifically formulated to detect O157:H7.
Pathogenic E.
coli (O157:H7) cannot ferment sorbitol while non-pathogenic E. coli can ferment both
soribitol and lactose. Therefore, colonies that ferment (acidic conditions; non-
pathogenic)
can be differentiated from non-fermenters (neutral to basic conditions; pathogenic).
✔✔What is the Gram status (positive or negative) of microbes growing on Eosin
Methylene Blue (EMB) agar plates? - ✔✔Gram-Negative. EMB plates specifically
restrict the growth of Gram-Positive bacteria.
✔✔Mannitol salt agar will turn what color in the presence of the pathogenic strain
Staphylococcus aureus? - ✔✔Yellow. Pathogenic Staph aureus will turn the agar from
red to
yellow.
, ✔✔Which non-selective yet differential agar plate should be used if a Streptococcus
sample is suspected? - ✔✔A BAP (blood agar plate) would be the quickest way to
identify and classify a potential streptococcus microbe based on its hemolytic
properties.
✔✔True or False. The Lancefield groups are used to subdivide antigenic groups of
alpha-hemolytic
Streptococcus - ✔✔False. The Lancefield groupings are used to subdivide beta-
hemolytic Strep.
✔✔In order to visual individual colonies of bacteria would you culture your sample in a
liquid media or on a solid (agar) media? Why? - ✔✔Solid (agar) media. The primary
advantage is that cells are held into place. When grown in a nutrient broth, bacterial
cells can multiply but are free to move around in solution. When grown on agar within a
petri dish the fixed in such as way as to form colonies.
✔✔True or False? The visualization of colonies on a petri dish represents bacterial cells
that have often multiplied a million times over. - ✔✔True. To form a bacterial colony the
initial
cell must have multiplied many times over, often greater than a million, in order for the
naked eye to resolve it
✔✔What disease can result if a patient with streptococcal pharyngitis goes untreated? -
✔✔Rheumatic fever occurs in approximately 3% of untreated cases of streptococcal
pharyngitis, presenting approximately 2-3 weeks post-infection.
✔✔True or False. The purpose of a quadrant streak is to expand a bacterial population.
- ✔✔False, The purpose of the quadrant streak is to generate individual colonies such
that a single (pure) bacterial sample can be isolated.
✔✔True or False. When performing a dilution streak a new (or sterilized) loop must be
used for each phase. - ✔✔True. Failure to do so would prevent the establishment of a
dilution
gradient, as the same bacterial concentration would be spread across both phase
regions.
✔✔Streptococcus, E. coli, pseudomonas, and klebsiella are all capable of causing what
disease? - ✔✔All of the above foreign microbes are capable of causing septicemia, also
known as blood poisoning.
✔✔You develop a fever, chills and pneumonia after recently using a warm midst
vaporizer in an
attempt to open your sinuses. What bacterial disease would a doctor suspect is causing
your
ANSWERS GRADED A+
✔✔What colors would you expect to see on an EMB plate containing E. coli? - ✔✔The
EMB plate itself is red in color while in the presence of E coli, the growing colonies will
take on a distinctive metallic green sheen.
✔✔While observing an unknown sample of limited amounts, a researcher must
determine the
following observations: (1) the presence of any motility and (2) its Gram status using the
same
sample—the liquid sample cannot be divided. Which would you determine first and
why? - ✔✔You must determine motility before determining the Gram status. Motility
requires a wet
mount, while Gram staining requires heat fixing the sample. If one were to begin with
the
Gram stain the heat fixation process would kill the organism, making any observations
regarding motility impossible. The correct approach would be to place the liquid culture
on a
glass slide and determine its motility status. Next, the same liquid culture can be heat
fixed
and Gram stained
✔✔What is the name of the process of spreading a bacterial culture onto a petri dish? -
✔✔Plating. Plating microbes can be done using a sterile loop, a sterile swab, or a
sterilized wire loop. Each device is simply a means of spreading the bacteria, most
commonly in a simple back-and-forth motion, across the plate.
✔✔What is the primary advantage of plating a bacterial culture as opposed to having it
grow in solution? - ✔✔The primary advantage of plating a bacterial sample onto agar is
that cells are held in place. Unlike in a nutrient broth where bacterial cells can multiply
but are free to move around in solution, bacteria plated onto agar are fixed in such a
way as to support the formation and visualization of colonies.
✔✔A researcher is studying a strain of E. coli currently growing on a MacConkey plate.
However, the researcher can't remember if E. coli is Gram-Positive or Gram-Negative.
Would a Gram stain be necessary to confirm? Why or why not? - ✔✔No. A Gram stain
would
not be necessary, as only Gram- Negative microbes will grow on MacConkey agar.
Thus, E.
coli is a Gram-Negative microbe
✔✔What is the purpose of the quadrant streak approach? - ✔✔The purpose of this
method is to generate an individual colony so that a single (pure) bacterial sample can
be picked from the plate.
,✔✔A facultative anaerobe is a microorganism capable of growth under what conditions?
- ✔✔A facultative anaerobe is capable of growth under aerobic (with oxygen) and
anaerobic
(without oxygen) conditions.
✔✔In a three-phase dilution gradient, which phase most likely contains individual
colonies: phase 1 (P1) or phase 3 (P3)? - ✔✔Individual colonies are most likely going to
appear within the phase 3 streaks. You begin with P1 (highest concentration), dilute
during P2 and then further dilute the sample in P3. However, it is possible to see
individual colonies in P2 if only a small portion of P1 was carried over into P2.
✔✔True or False: Differential media is best suited for distinguishing between two similar
species of bacteria. - ✔✔True
Growth media does not contain restrictive factors, while selective media is best used to
encourage the growth of one microbe while simultaneously discouraging the growth of
the other. Since two similar species of microbes are being studied they must be
differentiated under similar but just slightly different conditions (differential media).
✔✔True or False: Chocolate (cocoa) is not a component of Chocolate agar plates. -
✔✔True, The name is derived simply based on the color that actually comes from the
presence of 'cooked' (lysed) red blood cells in the media.
✔✔In an attempt to detect the presence of the pathogenic strain of E. coli O157:H7, a
researcher spread a culture onto a MacConkey agar with failed results. What type of
agar should they (correctly) try next? Why? - ✔✔The microbe should be plated on
SMAC
(Sorbitol-MacConkey agar) as it is specifically formulated to detect O157:H7.
Pathogenic E.
coli (O157:H7) cannot ferment sorbitol while non-pathogenic E. coli can ferment both
soribitol and lactose. Therefore, colonies that ferment (acidic conditions; non-
pathogenic)
can be differentiated from non-fermenters (neutral to basic conditions; pathogenic).
✔✔What is the Gram status (positive or negative) of microbes growing on Eosin
Methylene Blue (EMB) agar plates? - ✔✔Gram-Negative. EMB plates specifically
restrict the growth of Gram-Positive bacteria.
✔✔Mannitol salt agar will turn what color in the presence of the pathogenic strain
Staphylococcus aureus? - ✔✔Yellow. Pathogenic Staph aureus will turn the agar from
red to
yellow.
, ✔✔Which non-selective yet differential agar plate should be used if a Streptococcus
sample is suspected? - ✔✔A BAP (blood agar plate) would be the quickest way to
identify and classify a potential streptococcus microbe based on its hemolytic
properties.
✔✔True or False. The Lancefield groups are used to subdivide antigenic groups of
alpha-hemolytic
Streptococcus - ✔✔False. The Lancefield groupings are used to subdivide beta-
hemolytic Strep.
✔✔In order to visual individual colonies of bacteria would you culture your sample in a
liquid media or on a solid (agar) media? Why? - ✔✔Solid (agar) media. The primary
advantage is that cells are held into place. When grown in a nutrient broth, bacterial
cells can multiply but are free to move around in solution. When grown on agar within a
petri dish the fixed in such as way as to form colonies.
✔✔True or False? The visualization of colonies on a petri dish represents bacterial cells
that have often multiplied a million times over. - ✔✔True. To form a bacterial colony the
initial
cell must have multiplied many times over, often greater than a million, in order for the
naked eye to resolve it
✔✔What disease can result if a patient with streptococcal pharyngitis goes untreated? -
✔✔Rheumatic fever occurs in approximately 3% of untreated cases of streptococcal
pharyngitis, presenting approximately 2-3 weeks post-infection.
✔✔True or False. The purpose of a quadrant streak is to expand a bacterial population.
- ✔✔False, The purpose of the quadrant streak is to generate individual colonies such
that a single (pure) bacterial sample can be isolated.
✔✔True or False. When performing a dilution streak a new (or sterilized) loop must be
used for each phase. - ✔✔True. Failure to do so would prevent the establishment of a
dilution
gradient, as the same bacterial concentration would be spread across both phase
regions.
✔✔Streptococcus, E. coli, pseudomonas, and klebsiella are all capable of causing what
disease? - ✔✔All of the above foreign microbes are capable of causing septicemia, also
known as blood poisoning.
✔✔You develop a fever, chills and pneumonia after recently using a warm midst
vaporizer in an
attempt to open your sinuses. What bacterial disease would a doctor suspect is causing
your
