Lecture 9 Flashcards
Sterilization
Disinfection
Disinfectant
Germicidal
Bactericidal
Sporicidal
Fungicidal
Tuberculocidal
Decontamination
Antiseptic:
Bacteriostatic:
Sterilization-all forms of microbial life, including bacteria, viruses, spores and fungi, are killed
Disinfection-Less effective than sterilization
leaves spores
Disinfectant-chemical used mainly on inanimate objects to destroy or inhibit the growth of micro-organisms
Germicidal-An agent (disinfectant) that kills micro-organisms
Bactericidal: kills bacteria
Sporicidal: kills microbial/bacterial spores,
Fungicidal: kills fungi
Tuberculocidal: kills Mycobacterium tuberculosis
Decontamination: Process of removing disease-producing micro-organisms and rendering the object safe for handling
Antiseptic: Chemical that inhibits the growth of micro-organisms, or destroys them - agents used on the skin only
Bacteriostatic: inhibits the growth of bacteria but does not always kill them
Factors that Influence Degree of Killing
-Types of Organisms
-Number of Organisms
-Concentration of Disinfecting Agent
-Presence of Organic Material
-Nature (Composition) of Surface to be Disinfected
-Contact Time
-Temperature & pH
-Biofilms
-Compatibility of disinfectants and sterilants
The Ideal Disinfectants
-Kill the organism quickly
-Toxic to a wide spectrum of micro-organisms
-Non-toxic to humans & safe for the environment
-Active in presence of organic material (bacteria should not inactivate it the disinfectant)
-Act like a detergent (breaks up organic material)
-Water soluble (most are diluted with water)
-Effective at room temperature
-Non-corrosive
-Readily available & inexpensive
least susceptible -bacteria with spores and protozoa with cysts C diff, clostridium ,
most susceptible are vegetative bacteria or enveloped virus like herpes cmv, EpB, HIV, salmonella, staph
Medical Materials are classified into 3 devices
Critical devices:
Devices that enter vascular system or go into sterile tissue
Require sterilization
steam, dry heat
Semi-critical devices:
Devices that only touch mucous membranes
Require high level disinfection
2% gluteraldehyde
Non-critical devices:
Devices that only touch intact skin
Require low level disinfection-sodium hypochlorite, phenols
alcohols 60-95%
disinfection level,
mode of action
uses and considerations
disinfection level- low, intermediate
mode of action-denature proteins, dehydrate cells and make lipids soluble
uses-disinfectant for lab surfaces and hands -antiseptic
considerations-must be allowed to evaporate from the surface
aldehydes
glutaraldehyde
disinfection level,
mode of action
uses
considerations
disinfection level - high
mode of action - inactivates DNA and RNA
uses-disinfect metal objects and biosafety cabinets
considerations-does not corrode lenses, metal or rubber
halogens iodophors (iodine+polymer)
providine wash 5-10%
iodine tincture = iodine + alcohol
disinfection level,
mode of action
uses
considerations
disinfection level- low intermediate
mode of action degrade cell, wall, denature protein, coagulate chromosomal material
uses - skin prep for drawing blood, surgical hand scrub, pre-operative skin prep
considerations- must be diluted properly
Chlorine
Na
hypochlorite bleach at 05-1%
disinfection level,
mode of action
uses
considerations
disinfection level- high
mode of action - oxidizes the organism by damaging their proteins
uses-surface disinfectant 1:10 dilution used to clean blood spills
considerations-corrosive dont use on metals, require long contact to kill spores 10-60 min so dont use as a sterilant
inactivated by organic matter
Sterilization forms
Physical
Heat - dry
Hear- steam under pressure (moist heat)
Radiation –gamma or UV
Filtration
Chemical
Ethylene oxide gas (ETO)
Dry Heat – Hot Air Oven how does it kill
hot air oven - Kills by oxidation
Time-consuming and less effective than moist heat
Temperature: 160C for 120min or 170 C for 60min
Uses:
Oils, powders, empty glassware
Must be clean and free of all types of visible soil
Packaging should not insulate items from heat (paper bags, aluminum foil
Not for: fluids, culture media, linen wrapped packages, plastics or rubber - Do not package tightly, heat should circulate
Spore test is done with each load – use Bacillus subtilus
After sterilized incubate at 35C for 7 days – check for growth
Moist Heat- The Autoclave
Moist heat/steam is used to coagulate or denature microorganism proteins
Steam is under pressure of 15 psi because hotter than just steam at atmospheric pressure-bacteria killed in less time
Temperature & time: 121 C for 15 – 30min
Steps in autoclave operation:
Steam replaces air in chamber
Load is sterilized at the selected temp for set time
Steam is exhausted from the chamber
Load is dried and cooled after sterilization
What is/is not Sterilized in an Autoclave and QC
-Fluids
-Culture media
-Medical instruments not damaged by moist heat
-Rubber tubing must be rinsed in water so can create steam in the interior
-Laboratory garbage: autoclave bags cannot be too full- 135 C for 45 min
-Empty glassware must be on its side to let steam in
-Items can be unwrapped or wrapped
-Wrapping prevents recontamination after removal from autoclave
-Wrapping used must allow steam penetration - use paper or linen
-Must let wrapping dry after sterilization or will get contaminated
Items not sterilized in the autoclave:
-Medical equipment damaged by water or wet heat
-Oils and powders- repel moisture so no penetration
- plastic items will melt
-Serum – coagulates
-Blood for media that requires whole blood
QC of the Autoclave:
-Bacterial spore included with each load as biological indicator -Geobacillus stearothermophilus
-Monitor temp, time & pressure of each load
Non- ionizing Radiation – Ultraviolet
-Uses ultraviolet light to sterilize
-265 nm is optimal to kill bacteria
-Damages microorganism DNA
-Kills micro-organisms on exposed surfaces like operating rooms, sterile rooms, air conditioning ducts, surfaces of biological containment hoods
-Light must contact the organism to kill it -will not penetrate dust, paper
-Lack of penetration is why not used for plastic containers or glassware
Ionizing Radiation-Gamma Rays
-Generated from radioactive Cobalt 60 rods
-Ionizing radiation damages bacterial DNA
- penetrating
Used to sterilize:
Human tissue grafts
Medical equipment destroyed by heat
Foodstuffs
Pharmaceuticals
Plastic & tinfoil
Cardboard
Penetrates packaging, no toxic residue
But is expensive & there are some safety issues
Gas Sterilization -Ethylene Oxide (ETO)
-colorless & explosive mixed with nitrogen or CO2
- blocks bacterial metabolism (alkylating agent)
-Microorganisms are killed but spores need longer exposure
-Success of sterilization depends on gas concentration, temperature 37-63C, Humidity 40-80%, Time: 1-6 hours
-Used as a method of last resort for delicate or large instruments destroyed by steam or heat
Examples: plastics, electronics or large items like heart lung machines, infant incubators, mattresses & pillows
-Not often used due to lengthy cycle and its potential hazard
