Exam 1: Sterilization and Disinfection Flashcards
Sterilization
All forms of microbial life killed including spores.
Disinfection
Most infectious agents killed on inanimate surfaces.
Generally fail to kill spores, mycobacteria, and hepatitis viruses.
Sanitization
The overall lowering of the number of bacteria to safe levels.
Antiseptics
Substances that kill or prevent growth of microorganisms on living tissue.
Effect on skin is temporary due to recolonization from pores and ducts.
Pasteurization
Use of heat to kill certain pathogenic bacteria.
- 62° C for 30 minutes or 74° C for 3-5 minutes
- Includes Salmonella, Mycobacterium, Listeria, Strep, Brucella, Campylobacter
- Does not kills spores
- Reduces overall bacterial content by 97-99%
Germicide
Agent that kills microoganisms.
Analogous to disinfectant/antiseptic.
- Bacteriocide ⇒ kills bacteria
- Sporicides ⇒ extends activity to spores
- Viricide ⇒ kills viruses
- Fungicide ⇒ kills fungi
- Tuberculocide ⇒ kills mycobacteria
Pyrogens
Microbe-derived contaminants that cause fever when injected.
- Low MW
- Not removed by filtration
- Survive autoclaving
- Pyrogen free = never had microbial growth present
- Heating contaminated fluids ⇒ lysis and release of endotoxin
- Sterilization by filtration better
- Ex. LPS from dead bacteria
High Level
Germicides/Disinfectants
Effective against vegetative bacteria, fungi, viruses, AND spores.
May require prolonged contact time or high concentrations.
Intermediate Level
Germicides/Disinfectants
Not effective against bacterial spores but effective against vegetative bacteria, fungi, and many viruses.
Low Level
Germicides/Disinfectants
Effective against most vegetative bacteria, some fungi, and some viruses.
Limited in their activity.
Order of Resistance
Descending order of resistance to disinfection/sterilization:
Moist Heat
- Autoclaving ⇒ most common method of sterilization in hospitals
- Rapid & inexpensive
- Can penetrate clumps of organic material
- Steam under 15lbs/sq. in
- Temp of 121 °C for 15-20 minutes
- Best way to kill bacterial spores
UV Radiation
-
Causes nicks or thymine dimers in DNA
- Inhibits transcription and replication
- Unable to penetrate liquids and solids
- Limited usefulness
- Most often used for airborne contamination
- Staph and spore-formers relatively UV-resistant
Ethylene Oxide
- Gas used to sterilize surgical/medical equipment that cannot autoclave due to heat sensitivity
-
Acts as alkyating agent
- Adds alkyl group to amino groups of proteins and nucleic acids
- Can be sporicidal
- Can penetrate porous material
- Time required after treatment to allow residual ethylene oxide to aerate out
- Gas is toxic, flammable, and mutagenic
Phenolic Compounds
- Intermediate to low level disinfectants
- Act by denaturing protein-membrane complexes
- Use limited to general housekeeping & noncritical items
- Remains active in presence of organics and after prolonged drying
- Absorbed through porous material ⇒ may irritate tissues
- Not used on instruments that contact mucous membranes
Quaternary Ammonium
Compounds
- Low level disinfectant
- Acts as “cationic detergents”
- Dissociate to NH4+ that disrupts membrane phospholipids
- Poor activity against Gram ⊖
- No activity against spores or mycobacteria
- Inactivated by organic matter
- Use limited to noncritical items
- Ex:
- Benzalkonium chloride ⇒ topical disinfectant
- Cetylpyridinium chloride ⇒ mouthwashes
Biquanides
“Chlorhexadine”
- Antiseptic used as surgical scrub, hand wash, and superficial skin wound cleaner
- Can be incorporated into catheters etc
- Structure & action similar to quaternary ammonium compounds
- Cationic agents that disrupts membrane phospholipids
Chlorine Compounds
-
Releases free chlorine
- Reacts with water ⇒ hypochlorous acid
-
Strong oxidizing agent
- Inactivates proteins via sulfhydryl groups
-
Intermediate level @ high concentrations
- Used for spot disinfection
- 1-5% bleach solutions ⇒ tuberculocidal & viricidal
- But corrosive
-
Low level @ low concentrations
- Used to treat water
Iodine Compounds
- Halogen that oxidizes protein sulfhydryl groups
- Low to intermediate level depending on concentration
- Iodine dissolved in 2% alcohol ⇒ tincture
- Activity against most bacteria including mycobacteria
- Iodine + organic carrier ⇒ iodophore
- Carrier slows release of free iodine
- Increases effective time
- Decreases toxicity
- Ex. povidone iodine (Betadine)
Alcohols
- Disrupts membranes & denatures proteins
-
Ethyl & isopropyl alcohols @ 70% ⇒ intermediate level
- Tuberculocidal
- Limited action against some viruses
- No activity against spores
-
Useful as antiseptics
- Rapidly drying
- Inexpensive
- No residue
