Control of Microbial Growth

Question 1

decontamination/infection

Answer 1

-nuetralization or removal of microbes
-goal is to reduce number/impact of potentially harmful organisms

Question 2

sterilization

Answer 2

-processing of killing all microorganisms
-sterility can be thought of as binary, its either sterile or it isnt

Question 3

decimal reduction time

Answer 3

amount of time it takes to reduce number of microbes by a factor of 10
-depends on pH, salt concentration, moisture levels, presence of fats/sugars proteins in samples (can decrease heat penetration)

Question 4

decima reduction time and food safety

Answer 4

Question 5

pastuerization

Answer 5

-prevent spoilage and protect against food borne pathogens with certain foods and beverages
-heated for a specific amount of time to eliminate pathogens and to reduce spoiling agents

Question 6

milk pasteruization time

Answer 6

-71C for 15seconds
-balances between minimal loss of food quality and safety
-not sterilization
-heat resistant lactic acid bacteria survive pastuerization and are what cayse the milk to spoil over time

Question 7

autoclaves

Answer 7

-sterilization
-use steam to sterilize by heat
-endospores require 121 for 15mins
-water (steam) is pressureized to increase boiling temp allowing it to be 121
-high pressure steam circulated through autoclave

Question 8

ultraviolet light

Answer 8

-damages DNA and is lethal to microbes at high enough intensities
-useful for sterilizing surfaces or aire, but poor penetrating power

Question 9

ionizing radiation

Answer 9

improved penetrating power and is used to sterilize surgical supplies labwear and food

Question 10

filtration

Answer 10

-passing liquids through fiters with pore size of 0.2microns is a common way to sterilize solutions
-high quality filters are very effective but not as reliable as autoclaving
-used for some applications in the lab instead of heat since heat can cause damage

Question 11

how do many chemical products work (also damage human cells)

Answer 11

-membrane disruption, protein denaturation, oidizing agent

Question 12

sterilizants

Answer 12

kill microbes
-formadelhyde

Question 13

disinfectants

Answer 13

-largely for surfaces, kill many/most microbes but not all
-lysol

Question 14

sanitizers

Answer 14

-similar to disinfectants but less harsh to human also generally less effective
-soaps

Question 15

antiseptics

Answer 15

-kill or inhibit growth of microbes, non toxic enough to use on tissues

Question 16

antimicrobial agent

Answer 16

chemical that kills or inhibits the growth of microbes

Question 17

cidal

Answer 17

-agent that kill cells
-irreversible

Question 18

static

Answer 18

-agents that do not kill but that inhibit growth
-prevent growth but microbes are not dead and can recover

Question 19

lytic

Answer 19

-agents that kill cells and cause them to lyse

Question 20

Minimum inhibitory concentration

Answer 20

-lowest concentration of a compound that fully inhibits microbial growth
-determined using serial dilutions of the compound

Question 21

zone of inhibition

Answer 21

-antimicrobial activity can also be assessed using solid media combined with disks that contain compound of interest
-disk places on agar plate and diffuses
-closer disk = higher concentration of antimicrobial agent
-the size of the zone of inhibition (area of no growth) indicated suceptibility to compound
-kirby bauer test

Question 22

antibiotics

Answer 22

-specific mechanisms to taget microbes rather than generic and non specific toxitcityes such as widely inactivating proteins or disrupting membranes
-topical antibiotics are antibiotics in creams
-other antibiotics are typically ingested and must not harm human cells
-generally a small molecule that target specific aspect

Question 23

alexander fleming

Answer 23

-discovered penecillin from mold on a contamination plate
-also discovered lysozyme

Question 24

sulfa drugs

Answer 24

first effective ingested Ab was protosil that inhibits folate biosynthesis (folate essential cofactor)
-not effective in test tibe only in live animals as protosil is a pro drug that must be processed by body into its active form (sulphanilamide)

Question 25

what are the general specific targets that antibiotics target

Answer 25

-cell wall synthesis
-translation, DNA replication, essential biosynthetic processes

Question 26

how does penecillin work

Answer 26

-inhibits pencillin binding proteins which are proteins that catalyze transpeptidation reaction that crosslink cell wall
-cell wall constanly remodeled in growing bacteria (autolysin proteins)
-penicillin prevents digested wall from being repaired - cell wall loses integrity and cells lyse due to osmotic pressure

Question 27

where do Ab come from

Answer 27

-microbes produce/secrete antibiotics as competition mechansim
-many AB are natural products isolated from microbes
-Streptomyces (actinomyces) have been a very rich source of Ab
-streptomyces are soil dwelling bacteria that produce large numbers of antibiotics

Question 28

why does streptomyces have antimicrobial secreting properties

Answer 28

-large genomes, many interesting biosynthetic gene clusters

Question 29

AMR

Answer 29

-for many pathogens, we are running out o foptions to treat multi-drug resistant strains

Question 30

4 main mechanisms of resitance

Answer 30

-modification of drug target
-enzymatic inactivation of drug
-preventing access to bacterial cell
-metabolic by pass

Question 31

how does a microbe become AMR

Answer 31

-altered genetically in a way that reduces sensitivity to Ab
-can occur due to mutation but msot commonly HGT
-improper use of Ab

Question 32

perisistance

Answer 32

-antibiotc sensitvie populations include rare cells that are transiently tolerance to Ab
-most Ab depend on metabolic activity and often growth in order to be effect, so if your not building a cell wall or inhibitng cell wall synthesis it is not effective
-peristers are genetically unchanged and can be killed bu AB once again after they emerge from tolerant state

Question 33

dormancy

Answer 33

-is a common route to peristance

Question 34

Persister vs resister