Dr Shahla Latif

Cleansing is the removal of soil or organic material from instruments and equipment & may be done, clinically, in four steps:

Rinsing the object under cold water

Applying detergent and scrubbing object

Rinsing the object under warm water

Drying the object prior to sterilization or disinfection

Ultrasonic washer removes fine soil.

Disruption of cell membrane

Protein Denaturation

Damage to DNA: alkylating agents

Concentration of the agent Length of time

DEATH IS THE INABILITY TO REPRODUCE

REMAINS OF DEAD BACTERIA??

Organic matter (such as vomit and feces) frequently affects the actions of chemical control agent

Disinfectant activity is inhibited by cold temperatures

Higher concentrations, though, are not always preferable to lower concentration (e.g., alcohols)

High-level Disinfection (sterilized) will come in contact with mucous membrane or nonintact skin)

enter sterile tissue or the vascular system must be sterile because any microbial contamination could transmit disease.

This category includes surgical instruments, cardiac and urinary catheters, implants, and ultrasound probes used in sterile body cavities.

Most of the items in this category should be purchased as sterile or be sterilized with steam if possible

Intermediate-level (some semicritical items1 and noncritical items)

This includes respiratory therapy and anesthesia equipment, some endoscopes, laryngoscope blades etc

 These medical devices should be free from all microorganisms; however, small numbers of bacterial spores are permissible.

Low-level (noncritical items; will come in contact with intact skin but not mucous membranes. 

bedpans, blood pressure cuffs, crutches and computer

Phenol Coefficient…

…compares efficacy to that of phenol,

Greater efficacy indicated with coefficient >1

…Salmonella typhi and Staphylococcus aureus commonly used to determine coefficients

Filter-Paper/Disk Diffusion method…

…placement of disinfectant impregnated filter paper on well-inoculated agar

Use-Dilution test…

Salmonella, Staph, Pseudo

…drying bacteria to surface followed by exposure to disinfectan ( 10min @200C) and subsequent washing and inoculation of sterile broth

Virucidal chemicals

Newcastle disease virus

Injected into embryonated chicken eggs

Alcohol: ethanol & isopropanol

Aldehydes: glutaraldehyde & formaldehyde

Biguanides: Chlorhexidine

Bisphenols: Triclosan & hexachlorophene

Halogen releasing compounds: chlorine & iodine compounds

Heavy metal derivatives: Silver & mercury compounds

Organic acids: Benzoic acid & propionic acid

Peroxygens: hydrogen peroxide, ozone,& peracetic acid

Phenols & Cresols

Quaternary ammonium compounds : Cetrimide & benzalkonium chloride

Vapor Phase: Ethylene oxide, formaldehyde & hydrogen peroxide

O-PHENYLPHENOL CRESOL LYSOL

BIPHENOLS Triclosan (soap) Hexachlorophene

(neurotoxicity)

Acts on lipid containing membrane (Plasma Membrane)

USE: Surface disinfectant pus, saliva & feces Hexachlorophene for Gram +ve

(neurological damage)

Chlorhexidine

USE: skin & MM

Iodine: commonly used as an antiseptic against all microbes, fungi, and viruses

It inhibits protein synthesis and oxidizes –SH groups of amino acids

Chlorine: Used as a disinfectant (10% bleach)

Hypochlorous acid (HOCl) is a product, formed in water, that is the active form of the disinfectant

Applied in treatment of drinking water, swimming pool, and sewage

Tincture of iodine (iodine+ potassium iodide+ ethanol)

Iodophors (iodine+detergent)Povidone-iodine (PVI) is a commonly available iodophor, usually sold as a 7.5–10% solution (1% iodine).

MECHANISM of ACTION: Cross-links sulfhydryl groups to inactive disulfide

USES: spot-disinfection of countertops and floors.

blood spills, laundry, dental appliances, hydrotherapy tank

Chlorine dioxide also has been used to control Legionella in a hospital water supply

Hypochlorite may either be added directly (i.e., in the form of bleach) or created within water by bubbling chlorine gas through the water

Chlorine gas - preferred for medium to large disinfection systems

Sodium Hypochlorite (liquid) - typically used for small disinfection systems and large swimming pools

Calcium Hypochlorite (powder, tablet) - typically used for private swimming pools

Ethanol (60-95%) IsopropylEffectively kill bacteria and fungi but not endospores

nor nonenveloped virusesFast acting, no residue (evaporate away), no staining In tinctures, they enhance the effectiveness of

other antimicrobial chemicals Flammable; also may damage rubber, plastic. USES:oral and rectal thermometers,hospital

pagers, scissors, and stethoscopes, rubber stoppers of multiple-dose medication vials or vaccine bottles

Mercury

Silver

Soaps are sodium or potassium salts of fatty acids, a natural product

Detergents, instead, are artificial surfactants

While soaps are always negatively charged, some detergents are negatively charged while others are positively charged

One example of a positively charged detergent are quaternary ammonium compounds (benzalkonium chloride)

Quats are cationic detergents act by disrupting lipid bilayers

Quats are bactericidal, fungicidal, viricidal (enveloped), and amoebicidal

Quats are most effective against Gram-positive bacteria

Quats do not kill endospores, Mycobacteria spp., nor non-enveloped viruses

Quats are rapidly inactivated by organics including cotton and soap

Zephiran Benzalkonium chloride,Cepacol Cetylpyridinium chloride

Quats as floors, furniture, and walls blood pressure cuffs

alkylation of sulfhydryl, hydroxyl, carboxyl, and amino groups of microorganisms, which alters RNA, DNA, and protein synthesis

USE medical equipment such as endoscopes , transducers, anesthesia and respiratory therapy equipment , hemodialysis proportioning and dialysate delivery systems

Glutaraldehyde is capable of effectiving sterilization—at room

temperature, even against endospores,

and even in the presence of organics,

but achieving sterilization requries

many hours of exposure…pH 7.5-8.5

H2O2: bacteria and body tissues contain enzymes (catalase) that inactivate hydrogen peroxide

However, the oxygen released upon inactivation can help oxygenate deep wounds and thus kill strict-anaerobe contaminants, e.g., Clostridium tetani

Ozone and peracetic acid are also oxidizing antimicrobial agents

They exert their effect by oxidizing cell macromolecules

Chlorine gas (Cl2)

Chlorine dioxide (ClO2)

Ozone (O3)

Ethylene oxide (C2H4O)…

USE & ADVANTAGES …is used for items damaged by heat or moisture …is not corrosive, not damaging to delicate

instruments, microscopes, disposable plastic instruments

…permeates porous materials …dissipates rapidly from material

DISADVANTAGES…but is costly, toxic, carcinogenic, explosive, and relatively lengthy process

• It has the ability to be absorbed by many materials

• EO is a liquid that, at room temperature, becomes a gas.

• TYPES of EO used for sterilization • 100% in undiluted unit dose cartridges • Mixtures of ethylene oxide include the

addition of inert gasses such as hydrochlorofluorocarbons (HCFC's) and carbon dioxide.

• Costs - ethylene oxide gas is more expensive per cycle than steam and most of the alternative sterilization methodologies

• • extended time to properly and safely aerate

devices (a complete cycle can take 12-16 hours) makes turnover of devices unrealistic.

• a small amount of liquid hydrogen peroxide, which is energized with radio frequency waves into gas plasma.

• Cycle time is 45-50 minutes depending on the load configuration. The temperature is below 122oF. (50oC.).

• • 59% hydrogen peroxide

Ozone sterilization was cleared for use in the US in 2004. It uses oxygen that is subjected to an intense electrical field that separates oxygen molecules into atomic oxygen. It then combines with other oxygen molecules to form ozone. At the end of the cycle oxygen and water vapor safely vent into room, leaving no toxic residues.

• Peracetic acid is FDA-cleared as a liquid chemical sterilant.

• cleared for processing of immersible, semi-critical and critical heat-sensitive medical devices, including multi-channel, flexible surgical endoscopes.

• The peracetic acid is provided in powder (dry) form in a single-dose container.  The container of powdered concentrate is punctured during the cycle, and the concentrate is diluted with water inside the processor chamber, creating the sterilant .

•   The use dilution enters the chamber and is heated at a temperature of approximately  46ºC- 55.5ºC for 6 minutes.

• The total cycle time is 23-25 minutes