RA1: Sterilization, Disinfection, & Antisepsis

Question 1

What are the highest incidence HAIs in recent years?

Answer 1

Antibiotic-resistant Gram positive bacteria and multi-drug resistant Gram negative

Question 2

Sources of HAIs

Answer 2

1. Human (self, other patients, staff, visitors, etc.)
2. Environment (fomites, food, water, air)
   - -Same routes of infection as other places and same organism can be transmitted by more than one route

Question 3

Methods for prevention of infection

Answer 3

1. Sterilization (most effective)
2. Disinfection
3. Antisepsis (least effective)
4. Pasteurization (used for liquids)

Question 4

What is sterilization used for?

Answer 4

Total destruction or physical removal of all microorganisms

Question 5

Methods of sterilization

Answer 5

• -Moist heat
• -Dry heat
• -Ethylene oxide gas
• -Irradiation

Question 6

Sterilization technique uses: moist heat

Answer 6

Often done with an autoclave, most widely used and most dependable; kills microbes by irreversibly denaturing proteins to cause single strand DNA breaks and compromise membrane integrity (NOT THE SAME AS BOILING!)

Question 7

How can prions be killed?

Answer 7

Boiling in NaOH for ten minutes then extended autoclaving

Question 8

Sterilization technique uses: dry heat

Answer 8

Done in oven, kills spores but not pyrogens (fever-inducing agents), used for materials that can be damaged by moist heat; kills microbes by irreversibly denaturing proteins to cause single strand DNA breaks and compromise membrane integrity

Question 9

Sterilization technique uses: ethylene oxide gas

Answer 9

Used for heat- and moisture-sensitive medical devices; kills by alkylating protein, DNA and RNA within cells to prevent normal cellular metabolism and replication

Question 10

Sterilization technique uses: irradiation

Answer 10

Used in lab safety cabinets, hospital operating rooms, ionizing, prevention of growth in water in apparatus like auto-analyzers; kills by eliciting DNA damage through production of free radical to block microbial replication

Question 11

What is disinfection used for?

Answer 11

Removing or killing most, but not all, viable organisms (normally doesn’t kill mycobacteria, viruses, fungi, or bacterial spores)

Question 12

High-level disinfection

Answer 12

Destroys all microorganisms except large numbers of bacterial spores and used for all devices that cannot be sterilized (ex. endoscopes, plastic surgical devices)

Question 13

High-level disinfectants

Answer 13

Glutaraldehyde, oxidizing agents such as peracetic acid, hydrogen peroxide, and chlorine compounds

Question 14

Intermediate-level disinfection

Answer 14

Not very effective against bacterial spores, used on semi-critical instruments that come into contact with mucus membrane or non-intact skin

Question 15

Intermediate-level disinfectants

Answer 15

Alcohols, iodine-containing compounds (iodophors), phenolic compounds

Question 16

Low-level disinfection

Answer 16

Can only kill most vegetative bacteria, clean non-critical instruments that contact only intact skin

Question 17

Low-level disinfectants

Answer 17

Quaternary ammonium compounds

Question 18

What is antisepsis used for?

Answer 18

Disinfection of skin surfaces to lower number of microorganisms

Question 19

Types of antiseptic agents

Answer 19

• -Alcohols
• -Phenolic compounds
• -Iodine-containing solutions
• -Chlorhexidine
• -Quaternary ammonium compounds
• -Triclosan

Question 20

Alcohols (antisepsis)

Answer 20

• -Ex. ethanol and isopropanol
• -Kill most microbes but not spores
• -Act by denaturing bacterial proteins or inhibiting synthesis of metabolites essential for rapid cell division
• -Clean skin before poking with needle

Question 21

Phenolic compounds (antisepsis)

Answer 21

• –Act by penetrating and disrupting cell wall in high concentrations and denaturing proteins and lipids in cell membranes to lyse cell
• -Kill most microbes but not spores

Question 22

Iodine-containing solutions (antisepsis)

Answer 22

• -Most effective skin antiseptics
• -Kill many microorganisms but not spores
• -Quickly penetrate cell wall of microorganisms and cause disruption of proteins and nucleic acid structure and synthesis

Question 23

Two major types of iodine (antisepsis)

Answer 23

1. Tincture of iodine – prepares skin prior to blood culture but irritates skin
2. Iodophors – combination of iodine and stabilizing agent or carrier (ex. povidone iodine); non-toxic

Question 24

Chlorhexidine (antisepsis)

Answer 24

• -Broad antimicrobial activity but slower rate of killing than alcohols
• -Membrane disruption is method of killing (no spore killing)
• -Prevents bloodstream infections in patients with central lines better than iodine

Question 25

Quaternary ammonium compounds (antisepsis)

Answer 25

• -Ex. benzalkonium chloride
• -Not very efffective
• -Attack energy-producing enzymes, denature cell proteins and disrupt cell membranes

Question 26

Triclosan (antisepsis)

Answer 26

• -Found in antiseptic soaps and some toothpastes
• -Active against bacteria including mycobacteria but not spores
• -Works by inhibiting bacterial lipid synthesis and disrupting cell membrane at high concentrations