Control of Microbial Growth

Question 1

what is sterilization?

Answer 1

destruction or removal of all viable organisms

Question 2

what is disinfection?

Answer 2

killing, inhibition, or removal of disease causing organisms`

Question 3

what are disinfectants?

Answer 3

agents, usually chemical, used for disinfection on inanimate objects (typically)

Question 4

what is sanitization?

Answer 4

reduction of the microbial population to levels deemed safe based on public health standards

Question 5

what is antisepsis?

Answer 5

prevention of infection of living tissue by microorganisms

Question 6

what are antiseptics?

Answer 6

chemical agents that kill or inhibit growth of microorganisms when applied to tissue

Question 7

how is chemo used as antimicrobial agents?

Answer 7

use of chemicals to kill or inhibit growth of microorganisms within host tissue

Question 8

what do -cidal agents do?

Answer 8

kills bacteria

Question 9

what do -cidal agents do?

Answer 9

kills bacteria

Question 10

what are examples of cidal agents?

Answer 10

bactericides, fungicides, and viricides

Question 11

what does -static indicate?

Answer 11

a growth inhibiting agent

Question 12

what is the pattern of microbial death?

Answer 12

microorganisms are not killed instantly
population death typically occurs exponentially
is a measure of an agents killing efficiency
make sure that viable but noncultural cells are dead

Question 13

what is decimal reduction time?

Answer 13

the time it takes to kill 90% of cells

Question 14

what does filtration do?

Answer 14

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

Question 15

what are membrane filters?

Answer 15

porous membranes with defined pore sizes that remove microorganisms primarily by physical screening

Question 16

what are some examples of air filters?

Answer 16

surgical masks
high-efiicienctb particulate air (HEPA) filters

Question 17

what are some examples of using moist heat as control?

Answer 17

pasteurization
boiling
steam sterilization

Question 18

what does moist heat destroy?

Answer 18

viruses, fungi, bacteria
NOT endospores

Question 19

how does moist heat work?

Answer 19

degrades nucleic acids, denatures proteins, and disrupts membranes

Question 20

steam sterilization

Answer 20

carried out above 100 degrees C which requires saturated steam under pressure
effective against all types of microbes

Question 21

pasteurization

Answer 21

controlled heating at temperature well below boiling
used for milk, beer, and other beverages
process does not sterilize but kills pathogens present and slows spoilage y reducing the total load of organisms present

Question 22

dry heat sterilization

Answer 22

less effective than moist heat sterilization, requires higher temperatures and longer exposure time
oxidizes cell constituents and denatures proteins
does not corrode glasswares and metal instruments as moist heat does

Question 23

what is an example of dry heat sterilization?

Answer 23

flaming out inoculating loops

Question 24

ultraviolet radiation

Answer 24

260 wavelength is most bactericidal
causes thymine dimers preventing replication and transcription
limited to surface sterilization because it doesn’t penetrate glass, dirt films, water, or other substances
used for water treatment

Question 25

ionizing radiation

Answer 25

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

Question 26

what has overuse of antiseptics caused?

Answer 26

selection for resistant bacteria

Question 27

phenolics

Answer 27

commonly used as laboratory and hospital disinfectants
act by denaturing proteins and disrupting cell membranes
tuberculocidal, effective in presence of organic material, and long lasting
disagreeable odor and can cause skin irritations

Question 28

alcohols

Answer 28

among the most widely used disinfectants, antiseptics, and sanitizers
bactericidal, fungicidal, but not sporicidal
can inactivate some viruses
denature proteins and possibly dissolve membrane lipids

Question 29

halogens (iodine)

Answer 29

skin antiseptic
oxidizes cell constituents and iodinates proteins
may kill endospores at high concentrations
skin damage, staining, and allergies may be a problem

Question 30

what is iodophor?

Answer 30

iodine complexed with organic carrier
released slowly to minimize skin burns

Question 31

halogens (chlorine)

Answer 31

oxidizes cell constituents
important in disinfection of water supplies and swimming pools, used in dairy and food industries, effective household disinfectant
destroys vegetative bacteria and fungi
gas is sporicidal

Question 32

heavy metals

Answer 32

mercury, silver, arsenic, zinc, copper
effective but usually toxic
combine with and inactivate proteins; may precipitate cell proteins

Question 33

quaternary ammonium compounds

Answer 33

detergents that have broad spectrum antimicrobial activity and are effective disinfectants
amphipathic organic cleansing agents

Question 34

what are cationic detergents?

Answer 34

effective disinfectants that kill most bacteria, but not M. tuberculosis or endospores
stable and non-toxic, inactivate by hard water and soap

Question 35

aldehydes

Answer 35

commonly used agents are formaldehyde and glutaraldehyde
highly reactive molecules
sporicidal and can be used as chemical sterilants

Question 36

sterilizing gases

Answer 36

used to sterilize heat-sensitive materials
microbicidal and sporicidal
ethylene oxide sterilization is carried out in equipment resembling an autoclave
vaporized hydrogen peroxide can also be used

Question 37

what are some examples of natural control mechanisms?

Answer 37

predation by Bdellovibrio
viral-mediated lysis using pathogen specific bacteriophage lysins
toxin-mediated killing using bacteriocins

Question 38

what are the conditions that influence the effectiveness of antimicrobial agents?

Answer 38

population size
-larger=longer to kill
population composition
concentration or intensity of an antimicrobial agent
-higher concentrations kill faster
contact time
-longer exposure=more killed
temperature
-higher temps=enhanced chem activity

Question 39

how does local environment affect the effectiveness of antimicrobial activity?

Answer 39

pH, viscosity, concentration of organic matter, etc., van profoundly impact effectiveness
organisms in biofilms are less susceptible