MMI 4 - Sterilization And Disinfection Basic Infection Control

Question 1

Definition of sterilization

And disinfection

Answer 1

Sterilization is the killing or removal of all microorganisms, including bacterial spores. It is an absolute germ free state.

Disinfection is the killing of many but not all microorganisms, specially bacterial spores are not killed.

Question 2

What is disinfectant and antiseptics?

Answer 2

Disinfectant is a chemical agent that is used for disinfection

Antiseptic is a chemical disinfectant, which can be safely applied to skin or mucous membrane and are used to prevent infection by inhibiting the growth of bacteria.

Question 3

Terms used
1. Sterilization vs disinfection

2. Disinfectant vs antiseptic

Answer 3

1. Sterilization - destroying all forms of life
   Disinfection- destroying pathogens or unwanted organisms
2. Disinfectant- antimicrobial agent used on inanimate objects
   Antiseptic - antimicrobial agent used on living tissue

Question 4

What is bactericidal and bacteriostatic?

Answer 4

A bactericidal is an agent with the ability to kill bacteria

A bacteriostatic has the ability to inhibit the growth or reproduction of bacteria.

Question 5

Example of cidal and static

Answer 5

Cidal - bactericidal, fundicidal, algacidal

Static - bacteriostatic, fungistatic, algastatic

Question 6

Means of microbial control
Agents vs processes
Example of agents and their description

Answer 6

Processes:

• sterilization
• disinfection

Agents

• bactericide - chemical that destroys bacteria except for those at the endospore stage
• fungicide - chemical that kill fungi spores
• virucide - chemical known to inactive viruses, especially on living tissue
• sporicide - an agent capable of destroying bacterial endospores
• germicide/microbiocide - chemical agents that kill microorganisms

Question 7

What is sepsis and asepsis?

Answer 7

Sepsis - the growth of microorganisms in the blood or other tissue

Asepsis- any practice that prevents the entry of infectious agents into sterile tissues and thus prevents infection

Aseptic techniques : practiced in healthcare; ranged from sterile methods to antisepsis

Question 8

Methods of microbial control used outside of the body

Answer 8

Sterilization
Disinfection
Decontamination (also called sanitization)
Antisepsis

Question 9

What are the cellular targets affected by physical and chemical agents?

Answer 9

Cell wall
Cell membrane
Cellular synthesis
Proteins

Question 10

What is the effect of agent on the cellular target at cell wall?
Examples of agents used

Answer 10

Effect :
Chemical agents can damage the cell wall by
- blocking its synthesis
- digesting the cell wall

Examples:
Chemicals
Detergent
Alcohol

Question 11

What is the effect of agent on the cellular target at cell membrane?
Examples of agents used

Answer 11

Effect:
- Agents physically bind to lipid layer of the cell membrane, opening up the cell membrane and allowing injurious chemical to enter the cell and important ions to exit the cell

Agents:
Detergents

Question 12

What is the effect of agent on the cellular target at cellular synthesis?
Examples of agents used

Answer 12

Effects:

• agents can interrupt the synthesis of proteins via the ribosomes, inhibiting proteins needed for growth and metabolism and preventing multiplication
• agents can change genetic codes (mutation)

Agents:
Formaldehyde
Radiation
Ethylene oxide

Question 13

What is the effect of agent on the cellular target at proteins?
Examples of agents used

Answer 13

Effect:

• some agents are capable of denaturing proteins ( breaking of protein bonds, which results in breakdown of the protein structure.
• agents may attach to the active site of a protein, preventing it from interacting with it’s chemical substrate.

Agents:
Moist heat
Alcohol
Phenolics

Question 14

What are the factors that influence efficacy of disinfection/sterilization?

Answer 14

1. Contact time
2. Physico-chemical environment (eg pH)
3. Presence of organic material
4. Temperature
5. Type of microorganism
6. Number of microorganisms
7. Material composition

Question 15

Antimicrobial procedure used for control of microbial growth is based on

Answer 15

Types of microbe
Extent of contamination
Environmental conditions
Potential risk

Question 16

Examples of organisms that are more resistant and require stronger measures for control

Answer 16

• endospores require chemical treatment for 10 hours

- Mycobacterium’s waxy cells are resistant to chemicals

Question 17

List down more resistant organisms to least resistant organisms towards control method

Answer 17

Endospore of bacteria
Mycobacteria
Cysts of protozoa
Vegetative protozoa
Gram-negative bacteria
Fungi, including most fungal spore forms
Viruses without envelope
Gram-positive bacteria
Viruses with lipid envelopes

Question 18

Explain extent of microbial population to the control method

Answer 18

• larger population takes more time to destroy

- usually 90% of the population is destroyed in a given period

Question 19

What are the environmental conditions needed for control method

Answer 19

1. pH
2. Temperature
3. Presence of
   
   • organics : blood
   • dirt
   • grease

• No 3 must be cleaned first, then controlled

Question 20

What are the items that contribute to potential risk of transmitting infectious agents? Description and examples

Answer 20

1. Critical items - have indirect contact with body tissues
   Ex: scalpels and needles
2. Semi critical items - have contact with mucous membranes but it does not penetrate
   Ex: endoscopes, endotracheal tubes
3. Non-critical items - have indirect contact with unbroken skin
   - countertops, stethoscope