Sterilization and Disinfection

Question 1

Sterilization =

Answer 1

= the ELIMINATION of all microbes on INANIMATE objects

Question 2

Disinfection =

Answer 2

= REDUCTION of microbial load on INANIMATE objects

Question 3

Antisepsis =

Answer 3

= REDUCTION of microbial load on ANIMATE (living) objects

Question 4

Method of Sterilization = (Indications)

1. Steam = ?
2. Ethylene oxide (EtO) = ?
3. Gas plasma (H2O2) = ?
4. Ionizing radiation = ?
5. Paracetic acid = ?
6. Cold chemical sterilization = ?

Answer 4

(Method of Sterilization) = Indication

1. = heat and moisture tolerant items
2. = heat and moisture INtolerant items
3. = heat INtolerant items
4. = most single-use, prepackaged items
5. = medical and surgical instruments, i.e. endoscope
6. = items containing metal, rubber, plastic, or lenses

Question 5

Steam sterilization =

Answer 5

= destroys microbes via protein denaturation
> dry heat takes a long time at a high temp = most items can’t tolerate it
> steam under pressure = decreases sterilization time

Question 6

Autoclave

Answer 6

• steam under pressure
• surgical instruments and other heat and moisture tolerant instruments
• microbe death depends on:
  
  • exposure time
  • temp
  • pressure
• standard = 121C (249F) @ 15psi x 15-30 mins
• ER/”flash” = 132C (270F) @ 27psi x 3 mins
• types = gravity displacement or prevacuum
• must clean items first!

Question 7

Ethylene oxide (EtO) sterilization =

Answer 7

= destroys microbes via alkylation

• efficacy depends on:
  
  • temp = 49-60C (120-140F)
  • gas concentration
  • time = 4 hr minimum
  • humidity = 20-40%
• items that are steam INtolerant, i.e. endoscope, plastics
• toxic! aeration is essential!
  
  • natural = 7 days minimum
  • mechanical = 12-18 hr
  • safe level = 10 ppm ….. smell it at 700 ppm

Question 8

Gas plasma (H2O2) sterilization =

Answer 8

• uses H2O2 58%
• low temp = 50C ….. good for heat sensitive/INtolerant items
• rapid = 1 hr ….. no aeration required
• all items that can be steam sterilized AND those that can’t
• limitation = gas can’t penetrate walls of items with lumens w/o special adapter

Question 9

Ionizing radiation sterilization =

Answer 9

= uses cobalt 60 gamma rays

• low temp
• $$$$$ = restricted to commercial use
• pre-packaged, single-use items
• items sterilized by radiation should not be re-sterilized by other methods = item could be damaged or unsafe

Question 10

Paracetic acid sterilization =

Answer 10

= protein denaturation

• items bathed in 0.2% paracetic acid sol’n at 50C inside automated machine
• medical and sx instruments including flexible endoscopes

Question 11

Cold chemical sterilization =

Answer 11

= alkylation of microbe proteins

• sterilization = immersion for 10 hours = can be used to truly sterilize something, not just disinfect as in cold pack
• disinfection = immersion for 10 minutes
• agents:
  
  • glutaraldehyde 2% - wear gloves, sterilely rinse, dry
  • ortho-phthalaldehyde (OPA) 0.55%
  • hydrogen peroxide 7.5%

Question 12

Disinfectant vs. Antiseptics =

Answer 12

• Disinfectants = reduce microbe load on INanimate objects

- Antiseptics = reduce microbe load or inhibit growth of microbes on LIVING tissue

Question 13

Alcohol (70% IPA or EA)

Answer 13

• antiseptic and disinfectant
• corrosive
  = denatures cell wall proteins and biomolecules
• bactericidal (-static at lower concs.)
• minimal residual activity (evaporates)
• less effective than PVI or CHG
• helpful to remove excess lipids on the skin

Question 14

Povidone-iodine (PVI)

Answer 14

• antiseptic and disinfectant
• stains
  = free iodine penetrates cell wall and replaces intracellular molecules
• tidal effects (bact, fung, spor, effective on viruses)
• 15 min contact time
• minimal residual activity (like alcohol)
• effectiveness decreased in presence of organic material
• sx prep = 10% sol’n
• wound mgmt = 0.1-1% sol’n

Question 15

Glutaraldehyde

Answer 15

• disinfectant only

- tissue rxn

Question 16

Chlorine compounds, i.e. hypochlorite (bleach)

Answer 16

• disinfectant and +/- antiseptic
• corrosive
• inactivated by organic debris

Question 17

Antiseptics:
Isopropyl alcohol (IPA) = 
Povidone-iodine (PVI) = 
Chlorhexidine (CHG) = 
Alcohol-based sol'ns (ABS) =

Answer 17

Bacteria Fungi Viruses Spores
IPA = + + + -
PVI = + (fast) + + + (clostridium!)
CHG = + (fast) poor poor -
ABS = + +/- +/- +/-

Question 18

Chlorhexidine (CHG)

Answer 18

- antiseptic
= affects microbe cell wall permeability > precipitation of intracellular proteins
-bactericidal: rapid, G+ and G-
- min activity on fung, virus
- not sporocidal
- activity increases with repeated use
- not inactivated by organic debris, alcohol, or soaps
- sx prep = 4% sol'n
- wound mgmt = 0.05% sol'n

Question 19

Alcohol-based solutions (ABS)

Answer 19

= MOA depends on combo of antiseptics in the prep

• superior antimicrobial activity to PVI, CHG, or IPA alone
• more residual activity than alcohol alone
• one-step process (“scrubless” = apply and let dry)