Unit 11 - Antisepsis

Disinfection

Disinfection

killing of many, but not all, microorganisms

corrosive phenol-containing compounds

used only on inanimate objects

ethanol and iodine

used on skin surfaces

Antiseptics

Chemicals used to kill microorganisms on the surface of skin and mucous membranes

Antiseptics

chemicals intended to reduce or destroy microorganisms on living tissue

Levels of Disinfection

• HIGH-LEVEL DISINFECTION

• INTERMEDIATE-LEVEL DISINFECTION

• LOW-LEVEL DISINFECTION

HIGH-LEVEL DISINFECTION

The destruction of all viruses, vegetative bacteria, fungi, mycobacterium, and some, but not all, bacterial spores

INTERMEDIATE-LEVEL DISINFECTION

The destruction of all mycobacteria, vegetative bacteria, fungal spores, and some nonlipid viruses, but not bacterial spores

LOW-LEVEL DISINFECTION

A process that can kill most bacteria (except mycobacteria or bacterial spores), most viruses (except some nonlipid viruses), and some fungi

Sterilization

killing or removal of all microorganisms, including bacterial spores, which are highly resistant

Antibiotics

taken inside

Sterilization

taken outside

Sterilization

• usually carried out by autoclaving

• 121 Celsius

• 15 lb/in2 for 15 minutes

Ethylene oxide

a low temperature gaseous process widely used to sterilize a variety of healthcare product

Ethylene oxide

disrupts cellular metabolism and reproductive processes of microorganisms

Ethylene oxide

penetrates breathable packaging

Ethylene oxide

suitable for the sterilization of a wide range of materials

Filtration

Intravenous solutions are sterilized by

Chemicals

vary greatly in their ability to kill microorganisms

Chemical agents

act primarily by one of the three mechanisms:

1. Disruption of the lipid-containing cell membrane

2. Modification of protein

3. Modification of DNA

Ethanol

widely used to clean the skin before immunization or venipuncture

Ethanol

• more effective at 70%

• Alcohol with water is more effective compared to alcohol alone

Detergents

“surface-active” agent composed of long-chain, lipid soluble, hydrophobic portion and a polar hydrophilic group, which can be a cation, an anion, or a nonionic group

Detergents

They interact with the lipid in the cell membrane through their hydrophobic chain

Phenol

the first disinfectant in the operating room (by Lister in the 1860s), but it is rarely used as a disinfectant today because it is too caustic

Hexachlorophene

a biphenol with six chlorine atoms, is used in germicidal soaps, but concern over possible neurotoxicity has limited its use

Cresol

the active ingredient in Lysol

Chlorine

used as a disinfectant to purify the water supply and to treat the swimming pool

Chlorine

active component of hypochlorite (bleach, Clorox), which is used as a disinfectant in the home and in hospitals

Chlorine

a powerful oxidizing agent that kills by cross-linking essential sulfhydryl groups in enzyme that form the inactive disulfide

Iodine

most effective skin antiseptic used in medical practice and should be used prior to obtaining a blood culture and installing intravenous catheters because contamination with skin flora such as Staphylococcus epidermis can be a problem

Tincture of iodine

(2% solution of iodine and potassium iodide in ethanol) is used to prepare the skin prior to blood culture

Iodophors

complexes of iodine detergent that are frequently used to prepare the skin prior to surgery because they are less irritating than tincture of iodine

Iodine

an oxidant that inactivates sulfhydryl-containing enzyme

Mercury and silver

the greatest antibacterial activity of the heavy metals and are the most widely used in medicine

Mercury and silver

They act by binding to sulfhydryl groups, thereby blocking enzymatic activity

Thimerosal and merbomin

which contains mercury, are used as skin antiseptics

Silver nitrate

useful in preventing gonococcal ophthalmia neonatorum

Silver sulfadiazine

used to prevent infection of burn wounds

Hydrogen peroxide

used as an antiseptic to clean wounds and to disinfect contact lenses

Hydrogen peroxide

oxidizing agent that attacks sulfhydryl groups, thereby inhibiting enzymatic activity

Formaldehyde

a 37% solution in water (Formalin), denatures protein and nucleic acids

Glutaraldehyde

10 times more effective than formaldehyde and is less toxic

Ethylene oxide

used extensively in hospitals for sterilization of heat sensitive materials such as surgical instruments and plastics

Strong acids and alkalis

kill by denaturing protein

Dyes

not only stain microorganisms but also inhibit their growth

Crystal Violet

which is used as a skin antiseptic

Malachite Green

• a triphenylamine dye like crystal violet, is a component of Löwenstein-Jensen’s medium

• e dye inhibits the growth of unwanted organisms in the sputum during the 6-week incubation period

Heat

kills by denaturating proteins, but membrane damage and enzymatic cleavage of DNA may also be involved

Moist-heat

• sterilizes at lower temperature than dry heat

• usually autoclaving, is the most frequently used method of sterilization

Dry Heat

• requires temperatures in the range of 180 C for 2 hours

• used primarily for glassware and is used less frequently than autoclaving

Pasteurization

• technically not a sterilization process

• used primarily for milk, consist of heating the milk to 62 C for 30 minutes

• sufficient to kill the vegetative cells of the milk borne pathogen

UV Light

• 250- 260 nm

• maximum absorption by the purine and pyrimidine base of DNA

UV Light

inhibits the DNA replication and the organism cannot grow

UV Light

used in hospitals to kill airborne organisms, especially in operating rooms when they are not in use

Bacterial spores

quite resistant and require a dose up to 10 times greater than the vegetative bacteria

X-rays

have higher energy and penetrating power than UV radiation

X-rays

used in medicine for sterilization of heat sensitive items, such as sutures and surgical gloves, and plastic items, such as syringe

Filtration

preferred method of sterilizing certain solution

Pyrogen

chemicals or agents that can increase fever

Filtration

• nitrocellulose and has a pore size of 0.22µm

• work by physically trapping particles larger than the pore size