PORTAGE LEARNING BIO 171 MODULE 5 EXAM
1. 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).
2. A researcher is asked to determine if a sample contains Neisseria meningitides. Knowing
Neisseria meningitides is slow growing and other foreign microbes may also be present in the
culture, which type of media would be best suited:
A. Growth media
B. Differential media
C. Selective media
D. Selective and Differential media
C. Selective media. If additional foreign microbes may be present in your sample and you
know Neisseria meningitides is slow growing, you must restrict the unwanted microbes while
supporting the growth of Neisseria meningitides. Thus, you are selectively encouraging one
microbes growth, while selectively restricting others.
1. True or False: LB agar is classified as a selective, non-differential media.
False. LB agar is the most basic type of agar and like LB media supports the growth of
virtually all microbes without restriction.
2. What is agar used for in microbiology?
Define the concept of universal precautions.
Universal precautions means any and all samples, whether known or unknown, are to be
treated as potentially hazardous (or pathogenic) materials.
What would a researcher be certain to note while analyzing a microbial sample?
1. Size and shape
2. Any observable motility
3. Gram status (positive or negative)
4. The presence of any chemical reactions
5. Changes in color localized to the organism or the surrounding media
6. Capture (or draw) images of any of the characteristics described above
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.
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.
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.
, What is a facultative anaerobe?
A facultative anaerobe is capable of growth under both aerobic (with oxygen) and
anaerobic (in the absence of oxygen) condition.
How can Staphylococcus be differentially tested?
Staphylococcus species are capable of growth in the presence of bile salts
A bacterial swab is taken from a patient with impetigo and streaked across an MSA plate.
Following incubation at 37C, what will be the color of the agar?
The causative agent of impetigo is staph aureus, a Gram-positive bacterium capable of
fermenting mannitol. Fermentation will lower the pH of the agar and change the dye
color from red to yellow.
If a patient were suspected to have tuberculosis (TB), which differential stain would you
select and why?
To stain for TB, one would utilize an acid-fast stain to best visual the foreign microbe. As
a mycobacterium tuberculosis would stain poorly (indeterminate) using the Gram stain.
According to the module, which mycobacterium infection will be treated free of charge
by the World Health Organization (WHO)?
Leprosy is completely curable using a multiple-drug therapy regimen consisting of
various combinations of the drugs dapsone, rifampin and clofazimine—all of which is
given free of charge.
What are the three main conditions caused by the botulism toxin?
1) Food- improperly canned, contaminated, low-acidic foods (green beans, corn)
2) Infant- eat contaminated food (honey)
3) Wound- colonize in puncture wound (injection site for heroin/ contaminated needles)
Why are infants (< 6 months) more susceptible to botulism?
Due to infants still maturing intestinal tract and lack of an adult microbiota, the bacteria
are able to colonize and produce the associated toxin.
What is the mechanism of action of the toxin produced by clostridium tentani (tetanus)?
The toxin acts on inhibitory neurons causing systemic muscle stiffness and spasms.
Muscle stiffness can be observed in the jaw (lock-jaw) or spread systemically (if left
untreated) to muscles relating to respiratory function.
What Gram-negative bacterium might you come into contact with in a unsanitary hot
tub?
Legionella is often associated with unclean water systems such as hot tubs, hot water
tanks and AC units. Notably, legionella can only be transmitted through water droplets
small enough to be inhaled.
What are the three forms of plague, and what regions do they affect?
Bubonic (lymph), pneumonic (lungs) and septicemic (blood). Bubonic plague is best
characterized by painfully swollen lymph nodes. Pneumonic plague affects the
respiratory system (lungs). The most rare of all three plagues, septicemic plague targets
the blood system and, if left untreated, will develop into a life-threatening illness as the
blood-borne bacteria can infect all major organs.
1. 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).
2. A researcher is asked to determine if a sample contains Neisseria meningitides. Knowing
Neisseria meningitides is slow growing and other foreign microbes may also be present in the
culture, which type of media would be best suited:
A. Growth media
B. Differential media
C. Selective media
D. Selective and Differential media
C. Selective media. If additional foreign microbes may be present in your sample and you
know Neisseria meningitides is slow growing, you must restrict the unwanted microbes while
supporting the growth of Neisseria meningitides. Thus, you are selectively encouraging one
microbes growth, while selectively restricting others.
1. True or False: LB agar is classified as a selective, non-differential media.
False. LB agar is the most basic type of agar and like LB media supports the growth of
virtually all microbes without restriction.
2. What is agar used for in microbiology?
Define the concept of universal precautions.
Universal precautions means any and all samples, whether known or unknown, are to be
treated as potentially hazardous (or pathogenic) materials.
What would a researcher be certain to note while analyzing a microbial sample?
1. Size and shape
2. Any observable motility
3. Gram status (positive or negative)
4. The presence of any chemical reactions
5. Changes in color localized to the organism or the surrounding media
6. Capture (or draw) images of any of the characteristics described above
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.
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.
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.
, What is a facultative anaerobe?
A facultative anaerobe is capable of growth under both aerobic (with oxygen) and
anaerobic (in the absence of oxygen) condition.
How can Staphylococcus be differentially tested?
Staphylococcus species are capable of growth in the presence of bile salts
A bacterial swab is taken from a patient with impetigo and streaked across an MSA plate.
Following incubation at 37C, what will be the color of the agar?
The causative agent of impetigo is staph aureus, a Gram-positive bacterium capable of
fermenting mannitol. Fermentation will lower the pH of the agar and change the dye
color from red to yellow.
If a patient were suspected to have tuberculosis (TB), which differential stain would you
select and why?
To stain for TB, one would utilize an acid-fast stain to best visual the foreign microbe. As
a mycobacterium tuberculosis would stain poorly (indeterminate) using the Gram stain.
According to the module, which mycobacterium infection will be treated free of charge
by the World Health Organization (WHO)?
Leprosy is completely curable using a multiple-drug therapy regimen consisting of
various combinations of the drugs dapsone, rifampin and clofazimine—all of which is
given free of charge.
What are the three main conditions caused by the botulism toxin?
1) Food- improperly canned, contaminated, low-acidic foods (green beans, corn)
2) Infant- eat contaminated food (honey)
3) Wound- colonize in puncture wound (injection site for heroin/ contaminated needles)
Why are infants (< 6 months) more susceptible to botulism?
Due to infants still maturing intestinal tract and lack of an adult microbiota, the bacteria
are able to colonize and produce the associated toxin.
What is the mechanism of action of the toxin produced by clostridium tentani (tetanus)?
The toxin acts on inhibitory neurons causing systemic muscle stiffness and spasms.
Muscle stiffness can be observed in the jaw (lock-jaw) or spread systemically (if left
untreated) to muscles relating to respiratory function.
What Gram-negative bacterium might you come into contact with in a unsanitary hot
tub?
Legionella is often associated with unclean water systems such as hot tubs, hot water
tanks and AC units. Notably, legionella can only be transmitted through water droplets
small enough to be inhaled.
What are the three forms of plague, and what regions do they affect?
Bubonic (lymph), pneumonic (lungs) and septicemic (blood). Bubonic plague is best
characterized by painfully swollen lymph nodes. Pneumonic plague affects the
respiratory system (lungs). The most rare of all three plagues, septicemic plague targets
the blood system and, if left untreated, will develop into a life-threatening illness as the
blood-borne bacteria can infect all major organs.
