front 1 Why is antimicrobic sensitivity testing done?
- To identify the bacteria causing an infection
- To
obtain all of this information
- To determine what
antimicrobials the patient is susceptible to
- To determine
what antimicrobials would be most effective for treating the
infection
| back 1 -
To determine what antimicrobials would be most effective for
treating the infection
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front 2 Which choice below briefly describes the Kirby-Bauer method of
antimicrobic sensitivity testing?
- broth disk elution
- disk diffusion
- minimal
inhibitory concentration testing
- broth dilution
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front 3 Resistant and nonresistant E. coli bacteria samples were
spread on the agar plates below and incubated for 24 hours. Select the
true statements from the list below.
- The resistant E. coli strain grows on streptomycin
negative plates.The resistant E. coli strain grows on streptomycin
negative plates.
- The nonresistant E. coli strain
grows on streptomycin negative plates.The nonresistant E. coli
strain grows on streptomycin negative plates.
- The
nonresistant E. coli strain grows the same on streptomycin
positive or negative plates.The nonresistant E. coli strain grows
the same on streptomycin positive or negative plates.
- The
resistant E. coli strain grows on streptomycin positive
plates.The resistant E. coli strain grows on streptomycin positive
plates.
- Both resistant and nonresistant E. coli
strain show no growth on streptomycin positive plates.Both
resistant and nonresistant E. coli strain show no growth on
streptomycin positive plates.
- The nonresistant E.
coli strain shows more growth on the streptomycin positive than
the resistant E. coli strain.
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The resistant E. coli strain grows on streptomycin
negative plates.The resistant E. coli strain grows on streptomycin
negative plates.
-
The nonresistant E. coli strain grows on
streptomycin negative plates.
-
The resistant E. coli strain grows on streptomycin
positive plates.
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front 4 How will you select and grow a resistant strain of E. coli
in this experiment?
- Samples of bacteria are taken from the culture and observed
under a microscope for signs of susceptibility or resistance. Those
that are resistant are separated and plated.
- A culture of
E. coli will be mixed with streptomycin so that the antibiotic can
alter the genetic composition of the bacteria
- Expose a
sample of E. coli to streptomycin by inoculating it onto a
streptomycin negative plate. Any colonies that grow will carry a
mutation for resistance.
- Expose a sample of E. coli to
streptomycin by inoculating it onto a streptomycin positive plate.
Any colonies that grow will carry a mutation for resistance.
| back 4 -
Expose a sample of E. coli to streptomycin by
inoculating it onto a streptomycin positive plate. Any colonies
that grow will carry a mutation for resistance.
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front 5 Bacteria from three different cultures were plated on agar plates
containing ampicillin, an antibiotic. The number of colonies that grew
on each plate can be seen in the graph below.
If you assume that 100 bacteria were plated on each plate, what
percentage of the bacteria on plate B were resistant to ampicillin?
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front 6 Mueller-Hinton agar plates are poured to a uniform thickness of 4mm.
Zone size interpretive criteria are based on Mueller-Hinton plates of
this thickness. If a plate had been poured that was 7 mm thick, how
would this affect the size of the zones of inhibition?
- The zone diameters would be unaffected.
- The zones
would be smaller.Correct
- The zones would be larger.
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The zones would be smaller
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front 7 A chemical compound, regardless of its source (either natural or
synthetic), that is capable of killing or inhibiting microorganisms is
referred to as
- semisynthetic.
- a chemosynthetic agent.
- an
antibiotic.
- an antimicrobial.
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front 8 Natural selection occurs when
- only when nonrandom mating occurs.
- when a small
number of individuals of a population break away and form a new
population.
- a new genetic variation occurs that allows
individuals to have a reproductive and survival advantage.
- a factor in the environment alters the genetic information in
DNA of all members of a species.
| back 8 -
a new genetic variation occurs that allows individuals to
have a reproductive and survival advantage.
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front 9 How does an antibiotic act as a selective agent in promoting
bacterial resistance?
- Bacteria with a random mutation that allows resistance to
that antibiotic are able to survive exposure and reproduce, passing
the resistance mutation on to subsequent generations of
bacteria.
- Exposure to a specific antibiotic causes a
mutation that allows the affected bacteria to survive and
reproduce, passing the mutation to future generations.
- Antibiotics are designed to selectively kill some bacteria
while promoting the survival of all others.
- A specific
antibiotic selects favorable mutations that promote susceptibility
to that antibiotic.
| back 9 -
Bacteria with a random mutation that allows resistance to
that antibiotic are able to survive exposure and reproduce,
passing the resistance mutation on to subsequent generations of
bacteria.
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front 10 Two agar plates, one containing the antibiotic streptomycin and one
without antibiotics, are inoculated with E. coli. After
incubation, the streptomycin negative plate has many bacterial
colonies, while the streptomycin positive plate has only a few
colonies. Samples of the colonies from the positive plate are placed
on another positive plate, and after incubation many colonies grow. In
this experiment, what is the selective agent?
- the agar medium
- the antibiotic streptomycin
- the period of incubation
- the E. coli
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the antibiotic streptomycin
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front 11 Let's say you inoculate four agar plates, each containing a different
antibiotic (A, B, C, and D), and you add a swab from a lesion taken
from a patient. After incubating the plates, you observe that plate A
has only a few colonies, while the others all have many colonies. How
do you interpret the results?
- Bacteria in the patient's sample carry a mutation that makes
them resistant to antibiotic A
- Bacteria in the patient's
sample are resistant to antibiotic A, but not B, C, and D
- None of these antibiotics are an acceptable choice to use to
treat the patient for this bacterial infection
- Bacteria in
the patient's sample are susceptible to antibiotic A but not B, C,
and D
| back 11 -
Bacteria in the patient's sample are
susceptible to antibiotic A but not B, C, and
D
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front 12 Which of the following apply to the development of streptomycin
resistance in E. coli?
- The E. coli population has genetic variation.
- The
selective agent is streptomycin.
- The mutation resulting in
streptomycin resistance is random.
- E. coli changes its gene
structure to become antobiotic resistant in the presence of
streptomycin.
| back 12 - The E. coli population has genetic variation.
- The
selective agent is streptomycin.
- The mutation resulting in
streptomycin resistance is random.
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front 13 Staphylococcus aureus with 11mm
Streptococcus pyogenes with 22mm
Staphylococcus aureus with 13mm
Pseudomonas aeruginosa with 17mm
Staphylococcus aureus with 16mm
Acinetobacter with 11mm | back 13 -
Resistant
-
Sensitive
-
Intermediate
-
Sensitive
-
Intermediate
-
Resistant
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front 14 Place the steps of the Kirby Bauer method of antimicrobic sensitivity
testing in the correct order.
- Tap down disks with sterile forceps.
- Dispense
antibiotic disks onto the inoculated surface using sterile forceps
or an automatic dispenser.
- Label a sterile Mueller-Hinton
agar plate with organisms name and your name.
- Measure
diameters of zones of inhibition and compare zone diameters to
interpretive charts and determine if S, I, or R.
- Incubate
for 18-24 hours at 35oC.
- Obtain a dilute
suspension of the organism in nutrient broth to use as the
inoculum.
- Using a swab, inoculate the agar plate uniformly by
swabbing in three directions.
| back 14 - Label a sterile Mueller-Hinton agar plate with organisms name
and your name
- Obtain a dilute suspension of the organism in
nutrient broth to use as the inoculum
- Using a swab,
inoculate the agar plate uniformly by swabbing in three
directions
- Dispense antibiotic disks onto the inoculated
surface using sterile forceps or an automatic dispenser
- Tap
down disks with sterile forceps
- Incubate for 18-24 hours at
35*C
- Measure diameters of zone of inhibition and compare zone
diameters to interpretive charts and determine if S, I, or R,
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