MICRO LAB TEST 6 MEDICAL MICROBIOLOGY AND GROWTH CONTROL
EXAM QUESTIONS AND ANSWERS
You are studying a bacterium found in the normal intestinal flora of humans and most other mammals,
and are doing an experiment to determine the optimum growth rate of this bacteria. You have
inoculated five nutrient broths, and are incubating one broth at each of the following temperatures:
5oC, 25oC, 38oC, 42oC, and 55oC. At which temperature would you predict to see the optimum growth
rate? - CORRECT ANSWER✅✅38C
Where would you predict an facultative anaerobe would grow in a tube of fluid thioglycollate medium? -
CORRECT ANSWER✅✅Throughout the tube
How is an antiseptic different from a disinfectant? - CORRECT ANSWER✅✅An antiseptic is used to
remove or kill microorganisms on tissue, whereas a disinfectant is used to remove or kill microorganisms
on inanimate objects.
You have placed cultures in an anaerobe jar, activated the gas pack, and sealed the jar. Later in the day
you check the jar and notice that the methylene blue strip is colorless. What does this indicate? -
CORRECT ANSWER✅✅An anaerobic environment has been successfully established within the jar.
Which of the following would be appropriately sterilized using UV radiation? - CORRECT
ANSWER✅✅stainless steel surface in biological safety cabinet used for media preparation
A bacterial species that cannot tolerate the presence of oxygen and will only grow in the absence of
oxygen is classified as a(n): - CORRECT ANSWER✅✅obligate anaerobe
A bacterial isolate is subcultured to two blood agar plates, one of which is incubated in an anaerobe jar,
and the other is incubated on a shelf in the incubator. After incubation, growth is observed on the plate
from the anaerobe jar, but there is no growth on the plate incubated on the incubator shelf. Based on
these results, how would this organism be categorized? - CORRECT ANSWER✅✅obligate anaerobe
Where would you predict an obligate anaerobe would grow in a tube of fluid thioglycollate medium? -
CORRECT ANSWER✅✅At the bottom of the tube
, UV light has ______ wavelengths than visible light waves, and its peak energy is at a wavelength of
______. - CORRECT ANSWER✅✅shorter; 254nm
The pink color in the top of the broth in an FTM tube indicate - CORRECT ANSWER✅✅the presence of
oxygen
Some organisms exhibit flexibility in terms of their energy harvesting reactions. If provided with oxygen,
they will obtain energy through aerobic respiration. If in an environment without oxygen, they will turn
to fermentation to satisfy their energy needs. These organisms are classified a - CORRECT
ANSWER✅✅facultative aerobes
Inoculated tubes of fluid thioglycollate medium should be placed in an anaerobe jar during incubation -
CORRECT ANSWER✅✅False
Place these steps in the order in which they will be performed when setting up a disk diffusion assay to
test the effectiveness of disinfectants and antiseptics. - CORRECT ANSWER✅✅1.Using a swab, inoculate
a suspension of the bacteria being tested onto an agar plate, spreading the inoculum over the entire
surface
2.Saturate sterile filter paper disks with the test chemical (disinfectant or antiseptic) and place onto the
inoculated agar plate.Repeat with each chemical being tested.
3.Incubate inoculated agar plates overnight to promote bacterial growth.
4.Observe plates to determine the presence of a zone of inhibition around each antiseptic or
disinfectant disk.
How are agar plates inoculated for disk diffusion testing of antiseptics and disinfectants? - CORRECT
ANSWER✅✅A swab is used to inoculate the entire surface of the plate, producing a lawn of growth
Why is antimicrobic sensitivity testing done? - CORRECT ANSWER✅✅To determine what antimicrobials
would be most effective for treating the infection
Which choice below briefly describes the Kirby-Bauer method of antimicrobic sensitivity testing? -
CORRECT ANSWER✅✅disk diffusion
EXAM QUESTIONS AND ANSWERS
You are studying a bacterium found in the normal intestinal flora of humans and most other mammals,
and are doing an experiment to determine the optimum growth rate of this bacteria. You have
inoculated five nutrient broths, and are incubating one broth at each of the following temperatures:
5oC, 25oC, 38oC, 42oC, and 55oC. At which temperature would you predict to see the optimum growth
rate? - CORRECT ANSWER✅✅38C
Where would you predict an facultative anaerobe would grow in a tube of fluid thioglycollate medium? -
CORRECT ANSWER✅✅Throughout the tube
How is an antiseptic different from a disinfectant? - CORRECT ANSWER✅✅An antiseptic is used to
remove or kill microorganisms on tissue, whereas a disinfectant is used to remove or kill microorganisms
on inanimate objects.
You have placed cultures in an anaerobe jar, activated the gas pack, and sealed the jar. Later in the day
you check the jar and notice that the methylene blue strip is colorless. What does this indicate? -
CORRECT ANSWER✅✅An anaerobic environment has been successfully established within the jar.
Which of the following would be appropriately sterilized using UV radiation? - CORRECT
ANSWER✅✅stainless steel surface in biological safety cabinet used for media preparation
A bacterial species that cannot tolerate the presence of oxygen and will only grow in the absence of
oxygen is classified as a(n): - CORRECT ANSWER✅✅obligate anaerobe
A bacterial isolate is subcultured to two blood agar plates, one of which is incubated in an anaerobe jar,
and the other is incubated on a shelf in the incubator. After incubation, growth is observed on the plate
from the anaerobe jar, but there is no growth on the plate incubated on the incubator shelf. Based on
these results, how would this organism be categorized? - CORRECT ANSWER✅✅obligate anaerobe
Where would you predict an obligate anaerobe would grow in a tube of fluid thioglycollate medium? -
CORRECT ANSWER✅✅At the bottom of the tube
, UV light has ______ wavelengths than visible light waves, and its peak energy is at a wavelength of
______. - CORRECT ANSWER✅✅shorter; 254nm
The pink color in the top of the broth in an FTM tube indicate - CORRECT ANSWER✅✅the presence of
oxygen
Some organisms exhibit flexibility in terms of their energy harvesting reactions. If provided with oxygen,
they will obtain energy through aerobic respiration. If in an environment without oxygen, they will turn
to fermentation to satisfy their energy needs. These organisms are classified a - CORRECT
ANSWER✅✅facultative aerobes
Inoculated tubes of fluid thioglycollate medium should be placed in an anaerobe jar during incubation -
CORRECT ANSWER✅✅False
Place these steps in the order in which they will be performed when setting up a disk diffusion assay to
test the effectiveness of disinfectants and antiseptics. - CORRECT ANSWER✅✅1.Using a swab, inoculate
a suspension of the bacteria being tested onto an agar plate, spreading the inoculum over the entire
surface
2.Saturate sterile filter paper disks with the test chemical (disinfectant or antiseptic) and place onto the
inoculated agar plate.Repeat with each chemical being tested.
3.Incubate inoculated agar plates overnight to promote bacterial growth.
4.Observe plates to determine the presence of a zone of inhibition around each antiseptic or
disinfectant disk.
How are agar plates inoculated for disk diffusion testing of antiseptics and disinfectants? - CORRECT
ANSWER✅✅A swab is used to inoculate the entire surface of the plate, producing a lawn of growth
Why is antimicrobic sensitivity testing done? - CORRECT ANSWER✅✅To determine what antimicrobials
would be most effective for treating the infection
Which choice below briefly describes the Kirby-Bauer method of antimicrobic sensitivity testing? -
CORRECT ANSWER✅✅disk diffusion
