5. Control of Microbial Growth

Question 1

disinfection

Answer 1

destruction or removal of vegetative pathogens but NOT bacterial endospores. usually used only on inanimate objects

Question 2

sterilization

Answer 2

complete removal or destruction of all viable microorganisms. used on inanimate objects

Question 3

antisepsis

Answer 3

chemicals applied to body surface to destroy or inhibit vegetative pathogens

Question 4

chemotherapy

Answer 4

chemicals used internally to kill or inhibit growth of microorganisms within host tissues
-antibacterials
-antibiotics
-antivirals
-antifungals

Question 5

impact of biocide exposure

Answer 5

most to least:
antisepsis
sanitization
disinfection
sterilization (moist heat, best/quickest way)

Question 6

“cidal” agents

Answer 6

kill

Question 7

static agents

Answer 7

inhibit growth

Question 8

pattern of microbial death

Answer 8

microorganisms are not killed instantly
population death usually occurs exponentially
measure of agent’s killing efficiency
-decimal reduction time: time to kill 90%
must be sure viable but nonculturable cells are dead
-once they recover, they may regain the ability to reproduce and cause infection

Question 9

D and Z values

Answer 9

D values are the time or dose required for a 90% reduction in microbial concentration via a sterilization process.
Z values measure the resistance of the microorganism to death by the sterilization source.

Question 10

Filtration

Answer 10

reduces microbial population or sterilizes solution of heat-sensitive materials by removing microorganisms
-also used to reduce microbial populations in air

ex: sterile glucose or sterile penicillin

membrane filters, filtering air

Question 11

moist heat

Answer 11

destroys viruses, fungi, and bacteria
boiling will not destroy endospores and does not sterilize
degrades nucleic acids, denatures proteins, and disrupts membranes

Question 12

dry heat is

Answer 12

less effective than moist heat sterilization, requiring higher temperatures and longer exposure times

Question 13

pasteurization

Answer 13

controlled heating at temperatures well below boiling
used for milk, beer, and other beverages
process does not sterilize but does kill pathogens present and slow spoilage by reducing the total load of organisms present
*increase shelf life

Question 14

ultraviolet radiation

Answer 14

wavelength of 260 is most bactericidal (DNA absorbs)
-causes thymine dimers preventing replication and transcription

UV limited to surface sterilization because it does not penetrate glass, dirt films, water, and other substances
-has been used for water treatment

Question 15

ionizing radiation

Answer 15

gamma radiation penetrates deep into objects (sterilizing foods)
destroys bacterial endospores; not always effective against viruses
used for sterilization and pasteurization of antibiotics, hormones, sutures, plastic disposable supplies, and food

Question 16

chemotherapeutic agents

Answer 16

chemical agents used to treat disease
destroy pathogenic microbes or inhibit their growth within host

Question 17

penicillin

Answer 17

gram positive activity; beta lactamase and acid sensitive
inhibits cell wall synthesis (“beta-lactam” antibiotics)

penicillin is a beta lactam
beta lactamase breaks down ring and stops action of beta lactam

Question 18

protein synthesis as a drug target

Answer 18

most of the antibiotics targeting protein synthesis will target translation by binding to the bacterial ribosome
-aminoglycosides
-tetracyclines
-marcolide antibiotics

Question 19

nucleic acid synthesis as a drug target

Answer 19

quinolones are antibacterial compounds that interfere with DNA gyrase
e.g. cirpofloxacin

Question 20

growth factor analogs

Answer 20

other antibacterial drug targets
structurally similar to growth factors but do not function in the cell
-analogs similar to vitamins, amino acids, and other compounds

Question 21

isoniazid

Answer 21

a growth analog effective only against mycobacterium
-interferes with synthesis of mycolic acid (only found in mycobacteria- acid fast)

Question 22

platensimycin

Answer 22

new structural class of antibiotic
broad-spectrum; effective against MRSA and vancomycin-resistant enterococci

Question 23

antibiotic targets that target the cell membrane and wall

Answer 23

polymyxins disrupt the membrane and cause leakage and death

Question 24

antibiotic targets that target peptidoglycan synthesis

Answer 24

beta-lactams
vancomycin
bacitracin

Question 25

b-lactams

Answer 25

penicillin, cephalosporin, derivatives
interfere with transpeptidation
(formation of cross-links)

Question 26

vancomycin

Answer 26

binds to pentapeptide precursor and prevents interbridge formation

Question 27

bacitracin

Answer 27

binds to bactoprenol and prevents new peptidoglycan precursors from reaching site of synthesis

Question 28

types of drug resistance

Answer 28

intrinsic
acquired
Persisters

Question 29

intrinsic

Answer 29

born with it in them
mycoplasma resistance to beta-lactam antibiotics and other cell wall inhibitors simply because these bacteria lack a cell wall
(no cell wall- walking pneumonia- should never be prescribed penicillin- useless since no cell wall)

Question 30

acquired

Answer 30

occurs when there is a change in the genome of a bacterium that converts it from one that is sensitive to an antibiotic to one that is resistance

Question 31

Persisters

Answer 31

drug-tolerant bacteria lack the mechanisms for antibiotic resistance and “ignore” the presence of antibiotics, usually because they are embedded in biofilms that antibiotics cannot effectively penetrate or are growing too slowly to be inhibited

Question 32

mechanisms of drug resistance

Answer 32

-modify the target of the antibiotic
-drug inactivation
-minimize the concentration of antibiotic in the cell
-bypass the biochemical reaction inhibited by the agent or increase the production of the target metabolite

Question 33

antiviral drugs

Answer 33

-drug development has been slow because it is difficult to specifically target viral replication
-antiviral drugs have had mixed success and the vast majority of viral infections cannot be cured
-some antiviral drugs simply limit the duration of the illness or its severity (flu and HIV)
-drugs currently used inhibit virus-specific enzymes and life cycle processes

Question 34

antiviral drugs for influenza

Answer 34

tamiful
-anti-influenza agent
-a neuraminidase inhibitor
-though not a cure for influenza, has been shown to shorten course of illness

Question 35

antifungal drugs

Answer 35

fewer effective agents because of similarity of eukaryotic fungal cells and human cells
-superficial and more common
-many have low therapeutic index and are toxic

easier to treat superficial mycoses than systemic infections
-combinations of drugs may be used