Chapter 8

Question 1

antimicrobial agent

Answer 1

any physical or chemical agent that either kills microbes or inhibits their growth

Question 2

Microbiocidial

Answer 2

antimicrobial agent that kils microorganisms, specifically it could be bacteriocidal, viricidial

Question 3

Microbiostatic

Answer 3

antiomicrobial agent that inhibits the growth of microorganims

Question 4

Sterile

Answer 4

something is sterile if its free of all viable microorganisms (removal or killing)

Question 5

Sterilization

Answer 5

process of killing and or removing all microorganisms in a material or object, including any spores

Question 6

disinfection

Answer 6

the process of decreasing the number of viable microorganisms on an inanimate object/surface to a level that presents a minimum possibility of disease transmission or contamination

Question 7

antisepsis

Answer 7

disinfection of living tissues

Question 8

sanitization

Answer 8

reduction of microbial population to levels deemed safe

Question 9

death for microorganisms

Answer 9

inability to reproduce (loss of ability to reproduce)

Mechanisms of death: alter physical state of cytoplasm, inactivate enzymes, disrupt cell membrane

Question 10

Conditions influencing effectiveness of antimicrobial agent activity

Answer 10

Population size=larger populations take longer to kill than smaller populations. Population composition=microorganisms differ markedly in their sensitivity to antimicrobial agents. Concentration or intensity of an antimicrobial agent. Duration of exposure. Local environment.

Question 11

Methods of Controlling Growth

Answer 11

Heat-high temps, one most effective and widely used ways kill microbes.heat denatures proteins, nucleic acids and cell membrane.Moist heat - (steam or hot water) - more effective than dry heat to kill.Sub boiling temperatures (Pasteurization) – mild heating to kill vegetative microbes, but does not sterilize (does not kill spores); disinfection

Question 12

Methods of controlling growth 2

Answer 12

) Boiling H2O - kill vegetative bacteria, many viruses and fungi; kills some spores (fungal);-doesn’t kill all endospores and some viruses; doesn’t strerilize (cause doesn’t kill all spores). Steam under pressure – heating water under pressure causes it to boil at higher temperatures than at normal atmospheric pressures

Question 13

Moist Heat

Answer 13

Destroys viruses, fungi, and bacteria
Boiling will not destroy spores and does not sterilize
Degrades nucleic acids, denatures proteins, and disrupts membranes

Question 14

Steam Sterilization

Answer 14

Carried out above 100oC which requires saturated steam under pressure
Uses an autoclave
Effective against all types of microorganisms (including spores!)
Quality control - includes strips with Geobacillus stearothermophilus

Question 15

Dry Heat

Answer 15

cause oxidation of organic constituents of cell
not as effective as moist heat - use when want no moisture
1) Oven - need higher temps and longer exposure times – 160-180 oC for 2 – 3 hrs in drying ovens can sterilize
Used for materials that can’t get wet (ie, glassware) but can get hot
2) Incineration – fire; burn materials (medical wastes, animal corpses); sterilizes
Flame loops

Question 16

Low Temperatures

Answer 16

primarily microbiostatic
Refrigeration - 4oC; for inhibiting microbial growth to extend shelf life; some slow growth by psychrotolerant mesophiles;doesn’t kill most vegetative cells or spores
Standard Freezing -20 oC – stops growth, but doesn’t kill all vegetative cells or spores; extends shelf life or foods or other products
Ultra-low temperature freezing - 80 oC; no microbial growth; more killing; but cells can survive if put into cryoprotectants (ie, glycerol); for very long term storage of cell lines, enzymes, viruses
Liquid Nitrogen- -196 oC; no growth; long term storage

Question 17

Filtration

Answer 17

pass liquid or gas through screen-like subs w/pores small enough to retain microbes, but let gas or liquid pass thru-filter out bacteria, fungi (0.44 µM or 0.22 µM pore size)
used to sterilize heat sensitive liquids or gasses which cannot be autoclaved (ie, certain medias, enzymes, antibiotics
usually use cellulose or nitrocellulose membrane filters, aka membrane filters for liquids
other filters, sterilize air -> HEPA (high effiiciency particulate air)

Question 18

Membrane filters

Answer 18

porous membranes with defined pore sizes that remove microorganisms primarily by physical screening
have replaced depth filters for the most part

Question 19

Radiation

Answer 19

Ionizing Radiation
Gamma irradiation, X-irradiation and electron beams are known as ionizing radiation because they are high energy and cause the production of ions in water (ie, -OH) and other materials. Gamma irradiation, X-irradiation and electron beams can sterilize (at high doses) or disinfect at lower doses.
Ionizing radiation can damage and denature proteins and DNA
Ionizing radiation can penetrate packaging; used to sterilize sealed medical equipment, food, and other things that can’t get hot or wet (ie, autoclaved)

Question 20

Radiation

Answer 20

Nonionizing Radiation
Ultraviolet radiation – is a type of non ionizing radiation – it is lower in energy so it does not produce ions; it can’t penetrate packaging and it can’t penetrate into spores; it does kill vegetative cells (260 nm damages DNA primarily)
Thus, it is best considered a type of disinfection; UV is useful in decontamination of surfaces
Cannot penetrate solid, opaque, or light-absorbing surfaces
Has been used for water treatment

Question 21

Dessication

Answer 21

remove H2O from microorganisms: drying vegetative cells stops metabolic activity
used to preserve some foods, chemicalss
dry fruits, beef jerkey, bread, dry grains to preserve
diff. microbes can survive for diff times after dessication
ie, Neisseria gonorrhoeae die w/in min after dessication
-Mycobac.tuberculosis -viable for hours or even days
-endospores viable indefinitely

Lyophilization – (freeze-drying) – dry out material with vacuum at same time lowering the temperature below freezing – for foods, cell lines
High salt or sugar –hypertonic environment dessicates microorganisms
- jelly, jam, salted fish
Smoking (cooking) – heat, drying plus toxic combustion products

Question 22

Phenolics

Answer 22

Derived from phenol (first disinfectant)
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 irritation
Triclosan is used in hand sanitizers

Question 23

Alcohols

Answer 23

Among the most widely used disinfectants and antiseptics
methanol - not a good antimicrobial agent (toxic and not very bactericidal)
concentrations of 70%-90% ethanol - are effective against vegetative forms of microbes (prokaryotes and fungi);but doesn’t kill endospores, so doesn’t sterilize
-70% ethyl alcohol used as common skin antiseptic against bacteria and fungi
-bacteriocidal props of alcohols increase with increasing carbon chain, but beyond propyl alcohol, they not too H2O sol, so not used too much as disinfectants
-propyl and isopropyl alcohol (40 -80 % sol) are bactericidal for veg cells
How w alcohols work ? 1) denature proteins; 2) also lipid solvents, so damage lipids in CM and damages CM

Question 24

Halogens

Answer 24

Any of five elements: fluorine, chlorine, bromine, iodine, and astatine
Important antimicrobial agents

Question 25

Halogens-Iodine

Answer 25

Skin antiseptic
Oxidizes and denatures cell constituents and iodinates proteins
At high concentrations may kill spores
Skin damage, staining, and allergies can be a problem
Iodophore
iodine complexed with organic carrier
released slowly to minimize skin burns
Tincture –iodine dissolved in ethanol

Question 26

Halogens-Chlorine

Answer 26

Oxidizes cell constituents especially proteins
Cl2 + H2O > HCL + HCLO (hypochlorous acid)
HCLO > H+ + CLO- (hypochlorite – very strong oxidizing agent that damages vital enzymes and other molecules)
Important in disinfection of water supplies and swimming pools, used in dairy and food industries, effective household disinfectant
Destroys vegetative bacteria and fungi,
Chlorine gas is sporicidal
Can react with organic matter to form carcinogenic compounds

Question 27

Heavy metasl

Answer 27

A) Mercury – use organic forms of mercury (organic mercury compounds)
Ie, mercurochrom (anitseptic) e, thimersal
B) (Silver Nitrate – AgNO3 (1 %)) – once used to as antiseptic in newborn’s eyes
C) Copper Sulfate - CuSO4 – used as algicide in reservoirs, swimming pools, municipal water supplies
4) Zinc sulfate – ZnSO4 – used as fungicides in agricultural uses
4) Zinc sulfate – ZnSO4 – used as fungicides in agricultural uses

Question 28

Soaps and Detergents

Answer 28

Emulsifying agents (amphipathic); make non polar molecules (lipids) more water soluble; helps physically remove microorganisms from clothing, skin and other surfaces
Also, helps to denature proteins and damage the cell membrane

Question 29

Aldehydes

Answer 29

Commonly used agents are formaldehyde and glutaraldehyde
Highly reactive molecules
Sporicidal and can be used as chemical sterilants
Combine with and inactivate nucleic acids and proteins
Used commonly as preservatives for animal matter

Question 30

Sterilizing Gases

Answer 30

Used to sterilize heat-sensitive materials
Microbicidal and sporicidal
Ethylene oxide sterilization is carried out in equipment resembling an autoclave
Betapropiolactone and vaporized hydrogen peroxide
Combine with and inactivate DNA and proteins