Unit Three : (CH 13) Contorlling Microbial Growth

Question 1

define and distinguish sterilization and disinfection

Answer 1

• sterilization is the process of killing or removing all forms of microbial life (including endoscopes) in a material or an object
• disinfection reduces the number of disease-producing organims from inanimate surfaces; usually involves the removal of vegetative or non-endospore forming pathogens

Question 2

what are the various forms of disinfection, based on surface/material being disinfected

Answer 2

• sanitiation disinfection of surfaces, materials, liquids to reduce microbial content to levels deem safe for public health
• antisepsis disinfection of living tissues (with solutions/materials generally called antiseptic, which are usually not as toxic)
• pasteurization heat treatment of food aimed at killing potential pathogens

Question 3

autoclave (moist heat)

Answer 3

• physical method

• chamber which is filled with hot steam (121 c) and pressure (15 lbs)

• preferred method of sterilization

• kills cells and endospores by denaturing proteins

• kills all microbes and endospores within 20 minutes

Question 4

define and distinguish between bactericidal and bacteriostatic

Answer 4

• bactericidal antibodies kill bacteria by inhibiting cell wall synthesis, bacterial enzymes or protein translation
• (group includes: beta-lactum, daptomycin, aminoglycosides, metronidazole, fluroquinolones & vancomycin)
• bacteriostatic antibiotics limit the growth of bacteria by interfering with bacterial protein production, dna replication, or other aspects of bacteria cellular metabolism
• (group includes: tetracyclines, sulfonamides, spectinomycin, trimethoprim, chloramphenicol, macrolide & lincosamides)

Question 5

define and distinguish between antibiotic and synthetic antimicrobial drugs

Answer 5

• antibiotic is a natural substance produced by a microbe
• synthetic is a substance that is chemically synthesized by humans in a lab

Question 6

what contributions did ehrlich, fleming, florey, and chain make to the field of antimicrobial medicine?

Answer 6

• enrlich (1910) synthesized salvarsan (arsenic derivative) that was used to treat syphilis
• fleming (1928) discovered the first antibiotic (penicillin)
• florey & chain produced first antibiotic as medication (penicillin)

Question 7

which was the first antimicrobial drug? the first antibiotic?

Answer 7

• first antimicrobial drug was salvarsan
• first antibiotic drug was penicillin

Question 8

what is the ecological role of antibiotics? (ie: why do bacteria and fungi produce them?)

Question 9

define selective toxicity. (use the unity of life argument to explain the challenge involved in killing bacteria that are infecting us)

Question 10

name and describe techniques that are used to measure the effectiveness of an antibiotic. for each technique, what are typical results and how are they interrupted?

Question 11

what is chemotherapeutic index?

Answer 11

refers to the dosage range expected to achieve desire effects in the average individual

Question 12

what is therapeutic does, and how does this relate to mic?

Answer 12

• refers to the minimum concentration of antibiotics to kill/inhibit microbe in patients
• it relates to mic because the higher concentration allows the mic to be maintain in host over a period of time

Question 13

what is toxic dose?

Answer 13

refers to the maximum concentration of antibiotics that is effective without causing adverse drug reaction of negative side effects (which are more likely to increase as concentration of drug increases)

Question 14

what do the terms broad-spectrum and narrow-spectrum antibiotics mean?

Answer 14

• broad-spectrum act against an extensive range of disease-causing bacteria by targeting both gram-positive/negative bacteria groups
• narrow-spectrum act against a limited group of gram positive/negative bacteria

Question 15

pasteurization (moist heat)

Answer 15

• physical method

• developed by louis pasteur

• is disinfection (doesn’t kill all microbes but slows/halts microbial growth)

• targets pathogens typically found in food (salmonella, brucella, & mycobacterium)

Question 16

incineration (dry heat)

Answer 16

• physical method

• kills cells and endospores by denaturing proteins (oxidation effects)

• effective way to sterilize disposable items (paper cups or dressings) & biological waste

Question 17

refrigeration (low temperature)

Answer 17

• physical method

• temperatures from 0 to 7oC

• bacteriostatic effect

• reduces metabolic rate of most microbes to prevent toxin reproduction or production

• inhibits most microbial growth but doesn’t kill pathogens (mostly mesophiles)

Question 18

filtration (physical separation)

Answer 18

• physical method

• removal of microbes by passage of a liquid or gas through screen like material with small pores

• sterilizes temperatures sensitive materials (vaccines enzymes, antibiotics & some culture media

Question 19

irradiation

Answer 19

• physical method

• electromagnetic radiation includes: electron beams, gamma-rays, x-rays, uv lights, visible light & infrared lights

• kills microorganisms by damaging/mutating dna

• used as sterilization or disinfection (depends on time, intensity, type of material)

Question 20

halogens (iodine, chlorine, bromine + fluorine)

Answer 20

• chemical method

• denatures proteins or lipid membranes

• found in common household products like bleach & iodine antiseptics

Question 21

alcohol (isopropanol & ethanol)

Answer 21

• chemical method

• kills bacteria & fungi, but not endoscopes or naked viruses

• acts by denaturing proteins and disrupting lipid-membranes

• found in common household products like clorox wipes & alcohol antiseptics

Question 22

ethylene oxide

Answer 22

• chemical method

• used to sterilize heat-sensitive, solid materials that can’t be autocalved

• kills all microorganisms and endospores by denaturing nucleic acids and proteins

Question 23

phenolics

Answer 23

• chemical method

• denatures protein or lipid membranes

• found in common household products like lysol & hand soaps

Question 24

detergent (surfactants)

Answer 24

• chemical method

• doesn’t kill microbe but does remove from surface

• found in common household products like laundry & dishwashing detergent

Question 25

cell wall (peptidoglycan) inhibitors

Answer 25

- β-lactam antibiotics (penicillins, cephalosporins, vancomycin, and carbapenems) - these all share a common 4-member ring known as the β-lactam ring that mimics the critical D-Ala D-Ala needed for cross-linking D-Ala to L-Lys - these antibiotics inhibit transpeptidase enzymes from recognizing terminal D-Ala D-Ala in the 5 sidechain sequence of a NAM-NAG carbohydrate polymer.

Question 26

explain in detail how penicillins (as well as semi-synthetic penicillins and cephalosporins) work to inhibit peptidoglycan synthesis. what is a beta-lactam ring?

Question 27

what does the enzyme penicillinase (also called βeta-lactamase) do?

Answer 27

a bacterial enzyme that breaks the bond in the β-lactam ring of penicillin to disable the molecule

Question 28

what are the disadvantages of the natural penicillins?

Answer 28

- narrow-spectrum: natural penicillins are mostly effective against gram-positive bacteria - susceptible to penicillinase

Question 29

for what purposes were the semisynthetic penicillins (i.e.: oxacillin, ampicillin, methicillin, etc.) created?

Answer 29

semisynthetic penicillins and cephalosporins were structurally modified to over come weakness of natural penicillins

Question 30

what does mrsa stand for? what characteristics does this bacterium possess?

Answer 30

- mrsa refers to methicillin-resistant staphylococcus aureus (or multiple-resistant s. aureus) - contains a gene in which allows s. aureus to be resistance to *multiple* natural/semisynthetic penicillins

Question 31

what does the acronym vrsa stand for?

Answer 31

- vrsa refers to vancomycin-resistant staphylococcus aureus

Question 32

what is the relevance of vancomycin? how does vancomycin differ from a beta-lactam antibiotic? how is it similar

Question 33

explain in detail the mode of action of gramicidin

Question 34

explain in detail the mode of action of Polymyxin B

Question 35

explain in detail the mods of action of quinolones

Question 36

explain in detail the mode of action of rifampicin

Question 37

why are there so few useful antibiotics that disrupt membranes or inhibit nucleic acid synthesis? (another way to think about this is: what makes gramicidin, polymyxin b, quinolones, rifampicin, etc. selectively toxic?)

Question 38

explain in detail how sulfa drugs (sulfonamides) prevent bacteria from synthesizing folic acid

Question 39

what do organisms use folic acid for (i.e.: why do these drugs kill bacteria)?

Question 40

explain in detail the modes of action of chloramphenicol, tetracyclines, streptomycin, and erythromycin

Question 41

explain why protein synthesis inhibitors are less selectively toxic (cause more side effects) than peptidoglycan synthesis inhibitors

Question 42

why is it even harder to target fungi and protozoans? What anti-fungal drug targets and options do we currently have available?

Question 43

why don’t we have drugs that cure viral infections? what anti-viral drug targets and options do we currently have available?

Question 44

when taking antimicrobial drugs, why are you instructed to take it at certain intervals (like every 4 hours)? what happens if you do not follow these instructions? (ie: how does that effect mic in the patient tissue/body?)

Question 45

when taking antimicrobial drugs, why are you instructed to take it over a period of several days to weeks (like for 10 days)? what can happen if you do not follow these instructions?

Answer 45

- antimicrobial drug is meant to kill off most of pathogens, but some will survive due to resistance - those that survive through are few enough that the immune system can deal with them - if you stop taking antimicrobial drug before instructed, you are allowing more cells the time to spread their resistance via hgt

Question 46

what is antibiotic resistance? how do antibiotic resistances originate? then, how are they typically passed from one bacterial cell to another?

Question 47

name the strategies that bacteria can use/evolve to evade an antibiotic (give an example of each)

Answer 47

- bacteria can evolve an altered target molecule so that the antibiotic can no longer bind (ex. slightly modify ribosome so antibodies like tetracyclines can't attach or interact with 70S ribosome) - bacteria can produce enzymes that inactivate/degrade the antibiotic (ex: production of penicillinase that breaks the β-lactam ring of penicillins and some semi-synthetic penicillins to inactive the antibiotic) - bacteria can block entry of antibiotic (ex: cell wall of gram-negative bacteria) -bacteria can have efflux pumps that pump the antibiotic out of the cell (ex: an antibiotic enters the microbe, which then pumps the antibiotic back out of the cell)

Question 48

what role(s) have humans played in the evolution of antibiotic resistances? what do the terms “misuse” and “overuse” mean?

Answer 48

- humans' role has increase the rate of the evolution of antibodies by due to the overuse and misuse of antibotics - **misuse** refers to the use of antibiotics for non-bacterial infections, whereas **overuse** refers is the use of antibiotics for mild infections (when the immune can eventually handle and clear the infection)

Question 49

membrane inhibitors