Dr Shireen Rafiq MBBS, M.Phil, Ph.D

The physical removal of soil e.g., dust, mud, organic material such as blood, secretions, excretions and microorganisms

It is accomplished with water, detergents

and mechanical action The terms “decontamination” and

“sanitation” may be used for this process

Bed pans (Salmonella, Shigella, Vibrio cholerae and Clostridia )

Respiratory therapy eqpt

Sputum -> Active TB

Blood spills

Medical eqpt

Blood -> HBV, HCV and HIV Surgical / Medical Instruments

Tissues / Fluids

Soil protects microorganisms from the chemical agent

Physical cleaning eliminates large numbers of microorganisms associated with soil

Effective cleaning is important for aesthetic reasons

Follow the label instructions when mixing and using a chemical

Have specific cleaning schedules of the work or care area

Disassemble object to be cleaned

◦ Equipment

◦ Instruments

◦ Environmental surfaces

Factors in cleaning action

◦ Chemical energy◦ (detergent)◦ Thermal energy (temperature)◦ Mechanical energy (friction)

Keep housekeeping surfaces visibly clean on regular basis

Clean up spills promptly

Clean and disinfect high-touch surfaces, such as doorknobs, bed rails, light switches, and surfaces in and around toilets on a more frequent schedule

Clean walls, blinds, and window curtains in patient-care areas when visibly soiled or dusty

CLEANING OF NURSERIES

CLEANING OF FLOORS 1 % of the microbes present on the floors are

pathogenic. On many occasion S. aureus. Isolated as a prominent

pathogen. Keep the mops dry when not in use

CLEANING OF SURGICAL PROCEDURES ROOMS CLEANING OF OT

A simple detergent reduces flora by 80 %

Addition of disinfectant reduces to 95 %

In busy Hospitals counts raise in 2 hours

Sodium hypochlorite blood and body fluids

Bleaching powder Toilets9grams/lit

To sterilize the operation theatre formaldehyde gas (bactericidal & sporicidal,viricidal) is widely employed as it is cheaper for sterilization of huge areas like operation theatres

The destruction of harmful microorganisms, usually other than bacterial spores, on inanimate objects by the use of a chemical agent.

chemical agents used are disinfectants.

Two broad classes ANTISEPTICS DISINFECTANTS

Antiseptics are non toxic for living tissues used for skin disinfection e.g spirit, alcohol,

iodine.

Basically the same chemicals as disinfectants but their reduced conc .e.g 70% Alcohol or 2%

Tincture of iodine.

Disinfectants Strong chemicals used to disinfect non living objects these are generally toxic and corrosive.

The disinfectants  are classified as high, intermediate, or low level, based on the effectiveness and contact time of the solution and the biocidal activity of an agent  against  bacterial  spores, mycobacterium  tuberculosis,  lipid and nonlipid viruses, and vegetative bacteria.

Nature of the Material

The easiest surface to disinfect is a  smooth ,nonporous, and cleanable one. If the materials are incompatible with disinfectant, damage and corrosion can occur

Bioburden

Under a given set of circumstances ,the higher the level of microbial contamination, the longer,required exposure to the disinfectant is needed.

Additionally, resistant micro-organisms require longer exposure times.

Organic Debris Present Blood, saliva, and other organic material

may contribute to the failure of a germicidal process by either direct inactivation of the disinfectant or the actual layering of the micro-organisms   on   the instrument or equipment, preventing penetration of the germicide.

Type and Concentration of the Germicide

Generally, the higher concentrations of a

chemical agent are more effective and require a shorter time to disinfect.

Can be expected to destroy all microorganisms, with the exception of high numbers of bacterial spores

Inactivates Mycobacterium tuberculosis, vegetative bacteria, most viruses, and most fungi, but does not necessarily kill bacterial spores

Kills most vegetative bacteria, most fungi, lipid and non-lipid viruses, but cannot be relied on to kill resistant microorganisms such as mycobacteria or bacterial spores.

Level of disinfection desired Biocidal properties Environmental factors Non-toxic, Non-irritating Soluble in water Pleasant odor Stability

Disruption of cell membrane. Alcohols Detergents Phenols

Modification of proteins chlorine iodine heavy metals hydrogen per oxide

Formaldehyde and Gluteraldehyde Ethylene oxide Acids and alkalis

MODIFICATION OF NUCLEIC ACIDS

Crystal violet used as skin antiseptic.

Malachite green dye inhibit the growth of unwanted micro organism in sputum and grow M. tubercluosis.

Alcohol Chlorines Iodophors Phenolics Quaternary ammonium compounds

They  are  classified  as  high-level disinfectants  or  sterilants.

Always wear impermeable gloves and protective , eyewear  when  handling  these  

solutions.

It s more effective than formaldehyde use to sterlize respiratory therapy equipment.

These solutions may be used for  high-level  disinfection  of  semicritical items that are not subject to corrosion.

It has a rapid action of 3 minutes for disinfection or 6 hours for sterilization.

It must be used with protective eyewear and gloves because it is extremely irritating to the eyes and skin

Chlorine is used to disinfectant to purify the water supply /swimming pools.

Hypochlorite(bleach) used in the home and

hospitals.

It is powerful oxidizing agent kills sulfhydryl gp in enzymes to form inactive disulfide.

Iodophors  are  classified  as  intermediate-level disinfectants.

Iodophor preparations are less irritating to tissues and cause less allergies.

Iodophor antiseptics are useful in the preparation of oral mucosa for local anesthesia, surgical procedures,and  hand washing.

Tincture of iodine (2% of iodine and potassium iodide in ethanol) is used on skin before blood culture.

It is irritating to skin should be removed with alcohol.

Phenolics are also classified as an intermediate- level disinfectant.

They  act  as  good surface spray cleaners and are effective in the presence of detergents.

Phenolics are useful on metal, glass, rubber, and plastic, and are less toxic and corrosive than glutaraldehyde solutions.

Phenols was the first disinfectant used in 0.T

bt it is rarely used nw as it is too caustic.

It not only damage membranes bt also denatures proteins.

Ethanol is widely used befor immunization and venipuncture.

It disrupts the cell membrane.

It require presence of water much effective at 70% than at 100%.

Used as antiseptic bt not as effective as iodine containing compounds.

Surface active agents long chain ,lipid soluble

hydrophobic and a polar hydrophilic .

It disrupts the cell membrane.

Quaternary ammonium compounds widely used as antiseptics.

It is available as 37% solution in water(formalin) denatures proteins and nucleic acids.

It is mostly used for preservative purpose.

This gas is used for heat sensitive materials sterlization of surgical instruments and plastics.

It is used as antiseptic to clead wounds and to disinfect contact lenses.

Its use is limited by the organism s containing catalase that degrades it.

Mercury and silver have the antibacterial activity widely used in medicines.

Silver nitrate drops useful in gonococcal opthalmia neonatorum.

Silver sulfadiazine to prevent infection of burn wounds.

The process by which all forms of microbial life, including bacteria, viruses, spores and fungi are destroyed.

It is usually carried out by autoclaving ,exposing to steam at121c under pressure of 15lb/in, for 15 min.

Instruments and materials used in penetration into normally sterile body parts.

Media, reagents and eqpt used in laboratory

practices

Instruments and materials used in penetration into normally sterile body parts

damaged by moist heat sterlized by exposure to ethylene oxide gas.

I.v solution are sterlized by filtration.

PHYSICAL AGENTS

Heat Ionizing radiation Filtration Gases Liquids

DRY HEAT Dry heat kills by oxidation (slow, uneven penetration). It kills by denaturing of proteins ,membrane damage and

enzyme cleavage of DNA may occurs. It includes sterilization by:

Incineration

Flaming

Red heat Hot air ovens

Microwave oven

Incineration 1200-1500 C,

pathological waste, surgical dressings, sharps, needles, other clinical wastes

Flaming Scalpels, neck of

flasks Red heat Inoculating loops,

wires

Hot air ovens 160-180 C for

one hour Glassware,

oily fluids, powder

Microwave

oven Not reliable

due to variable heat

Kills by protein coagulation (denaturation of enzymes) so requires lower temperatures and shorter times, but the moisture must penetrate the pathogens to be effective.

Water disrupts non covalent bonds e.g hydrogen bond which hold protein chain together.

It include Boiling Pasteurization Tyndallization Autoclave

Boiling At 100 C at sea level, kills

many vegetative cells and viruses within 10 minutes.

Pasteurization Destroys pathogens esp for

milk( Mycobacterium bovis , Salmonella typhi , etc.) without altering the flavor of the food sterilize at 62 C for 30min by rapid cooling.

Higher temperature short time pasteurization

It applies higher heat for a much shorter time (72 0 C for 15 sec)

UHT treatment An ultra-high-temperature,

very short duration treatment (140 0 C for 3 sec) is used to sterilize dairy products

Tyndallization Intermittent exposure at

100 C. Principle : One exposure

kills vegetative organisms, between heatings the spores become vegetative forms which get killed during subsequent heating

Gelatin media, media containing sugars.

It was invented by Charles Chamberland in 1879.

The name comes from Greek auto-,

ultimately meaning self, and Latin clavis meaning key — a self-locking device.

Autoclaving Steam applied under

pressure 15 lb/in square(121C for 15-20 min) is the most effective method of moist heat sterilization.

Kills highly resistant org( Clostridium botulinum) The steam must directly

contact the material to be sterilized

AN autoclave provides moist heat at 100c. At this temp vapour pressure equals the pressure

of the surrounding atmosphere i.e 760 mm Hg. Water is heated within a closed vessel,the

pressure inside inc. Steam thus formed is superheated,much more

than 100c. Superheated steam condenses on cooler

loads ,releasing thermal energy and moisture. Combined effect denatures the microbial

proteins.

STEAM is first intoduced into the jacket, kept filled through out the day at 121 c.

jacket is hot, the load is placed in the chamber. door is closed, steam allow to enter the

chamber. air and condensate start coming out of the

discharge channel,it reaches 121c temp steam trap is automatically controlled.

holding period starts as it endssupply of steam to the chamber is stopped,steam left in

Chamber cool pressure falls.

All part of the load must be permeated by steam ,the load should be loosely arranged.

Steam should be saturated and dry.

Minimum holding time for various temp and pressures necessary for complete sterlization.

Air must be completely removed from chamber and from the load so that load is subjected to pure steam.

Because damp heat is used, heat-labile products (such as some plastics) cannot be sterilized this way or they will melt.

Paper and other products that may be damaged by steam must also be sterilized another way.

Items should always be separat to allow the steam to penetrate the load evenly

Autoclaves are widely used in microbiology, medicine, tattooing, body piercing, veterinary science, mycology, dentistry, and prosthetics fabrication. They vary in size and function depending on the media to be sterilized.

Typical loads include laboratory glassware, surgical instruments, medical waste, and bateriological culture media.

It is very important to ensure that all of the trapped air is removed from the autoclave before activation as hot air is a very poor medium for achieving sterility.

Stat 134 °C can achieve in three minutes the same sterility that hot air at 160 °C takes two hours to achieve

A medical autoclave is a device that uses steam to sterilize equipment and other objects .This means that all bacteria, viruses, fungi, and spores are inactivated.

Autoclaves are found in many medical settings, laboratories, and other places that need to ensure the sterility of an object

Simple, NON Jacketed ;pressure cooker type. vertical or horizontal cylinder of metal in a

supporting frame. Cylinder contains water and a gas burner below cylinder heats it.Lid is fastened by screw clamps and made air tight.

Method of discharging air is in efficient.

Lacks the mechanism of drying the load after sterlization.

Autoclaves with automatic air discharge ;horizontal or vertical metal cylinder to which a door is fastened by a capstan head that operates by bolt.

Automatically remains locked while the chamber

pressure is raised.it has steam jacket which heats the side walls.

Vaccum system is provided in drying the load.An air intake channel with self-sterlizing

filter warm sterile air into the chamber.

Equipped with electrically driven pumps, produce vaccum in the chamber.

This allow the steam to pentrate very rapidly.

There are physical, chemical, and biological indicators that can be used to ensure that an autoclave reaches the correct temperature for the correct amount of time.

Chemical indicators on medical packaging and autoclave tape change color once the correct conditions have been met, indicating that the object inside the package, or under the tape, has been appropriately processed.

Biological indicators contain spores of a heat-resistant bacterium. If the autoclave does not reach the right temperature, the spores will germinate when incubated and their metabolism will change the color of a pH-sensitive chemical.

Physical indicators consist of an alloy designed after being subjected to a given temp for the relevant holding time. If the alloy melts, the change will be visible

Both ß and gama radiations are employed industrially for sterilization of large-scale pre-packed single use disposable items

Needles, syringes, latex catheters, surgical gloves

In food industry to reduce spoilage and remove pathogens

uv-light uv irridation inhibits DNA replication

and the organism could not grow. It occurs at 250-260nm.

X-rays X-rays have higher energy and

penetrating power than UV. It kills by production of free

radical,this break covalent bond in DNA.

It kill vegetative cells bt spores are resistant.

Surgical gloves,sutures,syringes and plastic items.

Removal of bacteria and other larger microorganisms from ‘liquids’ that are liable to be spoiled by heating

Blood serum, antibiotic solutions, i.v solutions

Removal of protozoal cysts

from drinking water, that are not destroyed by chlorination

Nitrocellulose filter(0.22um)

Ethylene oxide Highly penetrative,

microbicidal gas Used in industry to

sterilize plastics and other thermo-labile eqpt

Catheters, syringes

and prosthetic heart valve

Formaldehyde in combination with steam Used in hospitals to reprocess thermo-labile

eqpt.

Both processes carry toxic hazards

Categorizes how an object is disinfected by how the object is used:

◦ Critical◦ Semi-critical◦ Non-critical

Used on or in sterile areas of the body

Require sterilization

Cutting or dissecting devices Microsurgical instruments Cardiac catheters Implantables Dental Instruments IV Fluids IV catheters,needles,urinary catheters

All “critical” and “semi-critical” instruments should be sterilized by autoclave, dry heat or chemical vapor.

Used in or on mucous membranes or damaged skin

Require sterilization or high-level disinfection

Flexible endoscopes Laryngoscopes Endotracheal tubes Vaginal speculums Dental x-ray jackets ENT exam instruments Thermometers

May come into contact with patient’s intact skin

Intermediate or low-level disinfection

Room furniture Blood pressure cuffs and ambu bags Wheelchairs, stretchers Electronic thermometers Glucometers Stethescopes Bed pan ECG machine

They usually require chemical disinfection at least once daily

Use disposable barriers since they reduce the number of surfaces requiring disinfection.

If a non critical item gets visibly soiled with blood or other potentially infectious material,scrub it with detergent and water,dry it with a disposable towel and disinfect it with a low-level disinfectant like phenol,iodophore,bleach or alcohol

World Health Organization, 2000

◦ When instruments contact high infectivity tissue, single-use instruments recommended.

◦ If single-use instruments not available, maximum safety attained by destruction of reusable instruments.

◦ Where destruction is not practical, reusable instruments must be decontaminated by immersing in NaOH and autoclaved (121°C/30m), cleaned rinsed and steam sterilized.

◦ After decontamination by steam and NaOH, instruments can be cleaned in automated mechanical reprocessor.