micro 290 lab final\\ MICR 290 Lab Final
2025 – Study Guide & Practice
Questions
indicate three general methods you can kill germs & example
- physical (heat, radiation like UV rays)
- biological (antibiotic & phage)
- chemical (alcohol & bleach)
which structure of microbes are mostly damaged by UV light?
DNA
what type of lesion UV makes in the DNA of bacteria and what does it lead to?
thymine dimers which lead to mutation in DNA
what is the most lethal form of UV light and what is its wavelength?
UV-C; 100-290 nm wavelength
indicate the wavelength of UV light emitted by germicidal lamp. give examples of type of material that
these lamps are commonly used for to kill germs (sterilization)
254 nm used for sterilization of air, surfaces, water, & operating rooms
what happened to the bacteria when they were frozen? explain the outcome and reason for each type
of bacteria after they were irritated, heated, & dried.
because endospores of bacteria are very resistant to many harsh conditions including heat, dryness, &
UV light
definition of antibiotics
a type of antimicrobial agent that is made by a microorganism and kills or inhibit other microorganisms
what does efficacy of an antibiotic mean and how is it measured?
it means how effectively the antibiotics is killing or inhibiting the microbe of our interest. it is tested by
the kirby-bauer method which tests the sensitivity of bacteria to antibiotics
what is the definition of 'zone of inhibition' and how does it relate to the sensitivity of the microbes to
the tested antibiotic?
, if antibiotics inhibits the growth of the organism, a clear circular area appears around the disk. the
larger the diameter of the zone of inhibition, the more effective the antibiotic is in killing the organism
and a better choice for use in patients that are suffering from infections by that organism
which antibiotics has the greatest zone of inhibition and which one has the least?
C (largest clear ring) & B (smallest clear ring)
which would be your first choice for treating your patient?
C (largest clear ring)
if C is penicillin, and your patient is allergic to penicillin, which antibiotic would you use?
D (second largest clear ring)
which antibiotic would you not use?
B (smallest clear ring)
what type of agar is commonly used for the kirby-bauer test?
mueller-hinton agar
what is the science of epidemiology?
the study of causes, distribution and of disease in a population
outbreak
sudden and unexpected start of an infectious disease in a specific geographical area. for example,
outbreak of food poising in a restaurant
endemic
disease regularly and unexpectedly found among particular people or in a certain geographical area. for
example, malaria found in sub-saharan africa is considered due to the abundance of mosquitos (because
of the climate) that cause the disease
epidemic
widespread occurrence of an infectious disease in a community at a particular time beyond what is
expected. example: yearly cases of flu in CA
pandemic
multiple epidemics of the same disease throughout the world (in many countries) at the same time.
example: covid-19
indicate 3 ways that food that is provided to the public can be contaminated by harmful microbes?
- improper processing
- improper storage & transport
2025 – Study Guide & Practice
Questions
indicate three general methods you can kill germs & example
- physical (heat, radiation like UV rays)
- biological (antibiotic & phage)
- chemical (alcohol & bleach)
which structure of microbes are mostly damaged by UV light?
DNA
what type of lesion UV makes in the DNA of bacteria and what does it lead to?
thymine dimers which lead to mutation in DNA
what is the most lethal form of UV light and what is its wavelength?
UV-C; 100-290 nm wavelength
indicate the wavelength of UV light emitted by germicidal lamp. give examples of type of material that
these lamps are commonly used for to kill germs (sterilization)
254 nm used for sterilization of air, surfaces, water, & operating rooms
what happened to the bacteria when they were frozen? explain the outcome and reason for each type
of bacteria after they were irritated, heated, & dried.
because endospores of bacteria are very resistant to many harsh conditions including heat, dryness, &
UV light
definition of antibiotics
a type of antimicrobial agent that is made by a microorganism and kills or inhibit other microorganisms
what does efficacy of an antibiotic mean and how is it measured?
it means how effectively the antibiotics is killing or inhibiting the microbe of our interest. it is tested by
the kirby-bauer method which tests the sensitivity of bacteria to antibiotics
what is the definition of 'zone of inhibition' and how does it relate to the sensitivity of the microbes to
the tested antibiotic?
, if antibiotics inhibits the growth of the organism, a clear circular area appears around the disk. the
larger the diameter of the zone of inhibition, the more effective the antibiotic is in killing the organism
and a better choice for use in patients that are suffering from infections by that organism
which antibiotics has the greatest zone of inhibition and which one has the least?
C (largest clear ring) & B (smallest clear ring)
which would be your first choice for treating your patient?
C (largest clear ring)
if C is penicillin, and your patient is allergic to penicillin, which antibiotic would you use?
D (second largest clear ring)
which antibiotic would you not use?
B (smallest clear ring)
what type of agar is commonly used for the kirby-bauer test?
mueller-hinton agar
what is the science of epidemiology?
the study of causes, distribution and of disease in a population
outbreak
sudden and unexpected start of an infectious disease in a specific geographical area. for example,
outbreak of food poising in a restaurant
endemic
disease regularly and unexpectedly found among particular people or in a certain geographical area. for
example, malaria found in sub-saharan africa is considered due to the abundance of mosquitos (because
of the climate) that cause the disease
epidemic
widespread occurrence of an infectious disease in a community at a particular time beyond what is
expected. example: yearly cases of flu in CA
pandemic
multiple epidemics of the same disease throughout the world (in many countries) at the same time.
example: covid-19
indicate 3 ways that food that is provided to the public can be contaminated by harmful microbes?
- improper processing
- improper storage & transport
