Disinfection

Question 1

Sterilization

Answer 1

Killing of all micro-organisms (bacteria, fungi, virus)

Question 2

Germicide

Answer 2

Chemical agent used to kill organisms

Question 3

Disinfection

Answer 3

Use of germicide on inanimate object

Does NOT imply killing of all bacteria, just most pathogens

Question 4

Antisepsis

Answer 4

Use of germicide on human body

Kills or inhibits pathogens but does NOT kill everything

Question 5

Septic

Answer 5

Pathogenic bacteria in living tissue

vs aseptic

Question 6

Sanitize

Answer 6

Use of heat to lower bacterial content of object
(ex dishes, sheets)
Does NOT imply killing of all bacteria

Question 7

Preservative

Answer 7

agent used in small concentrations to inhibit growth

Question 8

Phenol coefficient

Answer 8

Measure of killing capacity compared with phenol

(minimal killing concentration, high coefficient = potent)

Question 9

Wet heat

Answer 9

More effective than dry (H2O disrupts H bonds -> denaturation)
Autoclave - kills everything including spores
- 121 C x 15 minutes (or longer for larger mass)
- monitor with test strips
- be careful with liquids…boiling

Question 10

Dry heat

Answer 10

Need higher temp and more time
Use if water would damage
ex: pasteurization (63C x 30 minutes)
- high temp short time (aka HTST, flash) - similar results
- test with alkaline phos (should be negative, denatures)
- kills Coxiella burnetii, Salmonella, Strep, Brucella, not spores

Question 11

Filtration

Answer 11

Used for heat-sensitive liquid
Inconvenient in large quantities
Ex: filter syringe
May not have consistent/exact pore size

0.45 microns - most bacteria, 0.22 microns only viruses

Question 12

Radiation

Answer 12

UV = non-ionizing - used in OR, hospital, etc
-> thymine dimers, peroxide, etc
- damaging to humans
- can’t penetrate other than air
X-ray, gamma - used for food but it tastes bad…

Question 13

Various physical methods

Answer 13

Drying
High osmotic pressure (ex sugar, salt in canned food)
Ineffective (ultrasound, baropressure, freezing/thawing)

Question 14

Gaseous sterilization

Answer 14

Ethylene oxide = alkylating agent (toxic)

- explosive, only used for dry materials

Question 15

Ethyl alcohol

Answer 15

Widest use
Optimum concentration = 60-70%
Denatures proteins, not 100% reliable, doesn’t kill spores
Isopropyl - more potent, less volatile, more expensive

Question 16

Halogens

Answer 16

Iodine -> oxidizes Tyr OH
 - used frequently for skin
Chlorine - water, swimming, food
 - traces rapidly lost
 - oxidizes Cys SH

Question 17

Cationic detergents

Answer 17

Disrupt cell membrans, lipid biofilms
Often leave biofilm in place
Don't work for Pseudomonas, TB
ex: quaternary ammonium salts
 - "Zephiran"

Question 18

Oxidizing agents

Answer 18

H2O2 - used for deep, anaerobic wounds
- ex gingival crevices
- antagonized by catalase (ex Staph)
K permanganate - used for urethra…?

Question 19

Phenols

Answer 19

Denatures proteins
Requires high concentrations
ex: Triclosan, Listerine

Question 20

Detergents

Answer 20

Anionic soaps remove bacteria (not cidal)
Antibacterial soap - includes triclosan
- inhibits lipid biosynthesis, resistance possible

Question 21

Metals

Answer 21

Generally bind SH groups
Silver salts (ex nitrate -> gonococcus)
Mercury -> minor skin wounds

Question 22

Dyes

Answer 22

Gentian violet = antifungal

-> candida, tinea

Question 23

Aldehydes

Answer 23

Formaldeyde -> vaccines

Glutaraldehyde -> blood-born hepatitis (ex “Cidex)

Question 24

Preservatives

Answer 24

Short chain or organic acids
Lactic, acetic, propionic, benzoic
Natural phenols (ex smoked)