6-4: Control of Microbial Growth (and death)

Question 1

What is decontamination/disinfection

Answer 1

Neutralizing or removing microbes. Goal is to reduce numbers of potentially harmful organisms

Question 2

What is sterilization

Answer 2

Process of killing all microbes. Either sterile (no microbes) or not

Question 3

What is decimal reduction time

Answer 3

Amount of time it takes to reduce number of microbes by a factor of 10

Question 4

What is thermal death time

Answer 4

Amount of time it takes to kill all cells at a given temperature

Question 5

Decimal reduction time/thermal death time both depend on…

Answer 5

pH, [salt], moisture, presence of fats/sugars/proteins

Question 6

What are autoclaves

Answer 6

Used to sterilized objects in healthcare, research using steam

Question 7

What temperature is required to kill endospores using autoclaves

Answer 7

121C for 15 minutes

Question 8

What is pasteurization

Answer 8

Heated for specific amount of time to eliminate pathogens and reduce spoiling agents

Question 9

What causes milk to spoil

Answer 9

Heat-resistant lactic acid bacteria that survive pasteurization

Question 10

What temp is milk pasteurized at

Answer 10

71C for 15 seconds

Question 11

What is ultraviolet light and ionizing radiation used for

Answer 11

UV = damages DNA and lethal to microbes at high intensities, sterilize surfaces but low penetration

Ionizing R = gamma rays, improved penetration , used to sterilize surgical supplies, labware

Question 12

What is filtration

Answer 12

Passing liquids through filters with pore size of ~0.2 microns to sterilized
Not as reliable as autoclaving, but does not cause damage like heat

Question 13

How do soaps/cleaners disrupt microbes

Answer 13

Membrane disruption, protein denaturation, oxidizing agents

Question 14

What are sterilants

Answer 14

Kill all microbes e.g. formaldehyde

Question 15

What are disinfectants

Answer 15

For surfaces, kill many/most but not all e.g. lysol

Question 16

What are sanitizers

Answer 16

Less harsh to humans, generally less effective e.g. soaps

Question 17

What are antiseptics

Answer 17

Kill or inhibit growth of microbes, non-toxic enough to use on tissues/wounds e.g. ethanol

Question 18

What is an antimicrobial agent

Answer 18

Chemical that kills or inhibits microbial growth

Question 19

Bactericidal vs bacteriostatic vs bacteriolytic

Answer 19

Cidal = kill cells
Static = inhibit growth, microbe not dead and can recover
Lytic = kills cells and cause them to lyse (no longer observable)

Question 20

What is the MIC of a compound

Answer 20

Minimal inhibitory concentration = lowest conc. of a compound that fully inhibits growth

Question 21

How can we assess antimicrobial activity

Answer 21

Solid media with antimicrobial disk placed on it, zones of inhibition

Question 22

What are antibiotics

Answer 22

Medicines/molecules with antimicrobial properties used to treat infections
Specific mechanisms to target specific aspect of microbial biology that is absent/different in humans

Question 23

What are topical antibiotics

Answer 23

Manufactured into creams/ointments

Question 24

Who discovered the first true antibiotic? How?

Answer 24

Alexander Fleming (penicillin). Mold was secreting compound that kills bacteria

Question 25

What was the first true antibiotic used in clinic

Answer 25

Prontosil

Question 26

How do antibiotics work

Answer 26

Target essential processes such as CW biosynthesis, translation, DNA replication, essential biosynthetic processes

Question 27

How does penicillin work

Answer 27

Inhibits penicillin binding protein activity, which catalyze transpeptidation reaction that crosslinks CW
Cell wall loses integrity, cells lyse

Question 28

What soil-dwelling bacteria produce a large number of antibiotics

Answer 28

Streptomyces

Question 29

How is antibiotic resistance a problem

Answer 29

Drugs that were once effective against pathogens unusable due to high resistance
Running out of options to treat MDR pathogen strains

Question 30

Four mechanisms of antibiotic resistance

Answer 30

1. Modification of drug target (enzyme mutation)
2. Enzymatic inactivation of the drug (degrade)
3. Preventing access to bacterial cell (efflux pump)
4. Metabolic bypass (find another way to do what the drug is blocking)

Question 31

How is persistence different than resistance

Answer 31

Persistence is when antibiotic-sensitive populations of bacteria include rare cells than are tolerant to antibiotics
Genetically unchanged, can be killed after emergence from tolerant state

Question 32

Common route of persistence

Answer 32

Dormancy (slowing/shutting off metabolism)
Antibiotics depend on metabolism/growth to be effective