1-12 Control of Microorganisms: Infection Control, Sterilization, and Disinfection

Question 1

What is the chain of infection, and what are its six links?

Answer 1

It is the transmission pathway of infection, which we seek to interrupt before completion.

The 1) agent leaves its 2) reservoir, or original host, through a 3) portal of exit. Through some 4) mode of transmission, it finds a 5) portal of entry to infect a new 6) susceptible host.

Question 2

What are the most common ways in which hospital-acquired infections (HAIs) are transmitted?

Answer 2

Direct contact with an individual who is infected, colonized, or a carrier.

Indirect contact with a contaminated object.

Respiratory transmission: airborne or droplet.

Question 3

What are the three sterilization/disinfection classifications of medical devices?

Answer 3

Medical devices are classified by their potential to transmit infectious agents.

• *Critical items** enter normally sterile parts of the body. They should be sterilized.
  ex) surgical instruments, invasive monitoring devices
• *Semicritical items** come in contact with mucous membranes or nonintact skin. They should be free of all microorganisms except spores (disinfection).
  ex) respiratory therapy, anaesthesia equipment
• *Noncritical items** come in contact with intact skin (NOT mucous membranes).
  ex) blood pressure cuffs, crutches.

Question 4

What are some physical means of sterilization?

Answer 4

• Steam sterilization (autoclaving)
• Dry heat sterilization
• Irradiation
• Filtration
• Gas sterilization
• Plasma sterilization

Question 5

What are some chemical means of sterilization and disinfection?

Answer 5

• Alcohols
• Halogens (chlorine and chlorine-releasing compounds, iodine and iodophors)
• Chlorhexidine
• Phenolics
• Quaternary ammonium compounds

Question 6

How do silver and copper alloy surfaces act against infection?

Answer 6

Metal ions combine with sulfhydryl groups.