Sterilizationanddisinfectioninhealthcare 120208060736-phpapp02

Dr.T.V.Rao MD

STERILIZATION AND DISINFECTION AN UPDATE

DR.T.V.RAO MD 1

HISTORY

• 1862 Invention of the Autoclave

• 1880 The first indicator : a potato

• 1906 Creation of the FDA

• 1925 Waxy pellets that melt at 121oC

• 1932 (ATI) CI with lead sulphite passes from black to white

• 1940 (ATI) CI Chromium TriChloride passes from purple to green

DR.T.V.RAO MD 2

HISTORY (CONT)

• 1960-70 Development of the Dvalue concept

using heat resistant spores for

sterilisation + Fvalue + Zvalue

• 1965 Proposal by Sweden of the SAL for a

definition of sterility

• 1979 Proposal by Canada of a legal

definition of sterility

DR.T.V.RAO MD 3

4

TERMINOLOGY IN STERILIZATION

• Sterilization – a process that destroys all viable

microbes, including viruses and endospores;

microbicidal

• Disinfection – a process to destroy vegetative

pathogens, not endospores; inanimate objects

• Antiseptic – disinfectants applied directly to

exposed body surfaces

• Sanitization – any cleansing technique that

mechanically removes microbes

DR.T.V.RAO MD

5

TERMINOLOGY IN STERILIZATION

• Degermation – mechanically removing microbes

form surface (skin) such as surgical hand

scrubbing, or wiping skin with alcohol prior to

venipuncture

• Sepsis – bacterial contamination

• Asepsis – absence of significant contamination

• Bactericidal (microbicidal) - -cidal means kill

• Bacteriostatic (micro biostatic) - -static means

inhibition of growth and multiplication

DR.T.V.RAO MD

AIM OF STERILIZATION - ASEPSIS

Asepsis is the practice to reduce or eliminate contaminants (such as bacteria, viruses, fungi, and parasites) from entering the operative field in surgery or medicine to prevent infection. Ideally, a field is "sterile" — free of contaminants — a situation that is difficult to attain. However, the goal is elimination of infection, not sterility.

• http://en.wikipedia.org/wiki/Asepsis

DR.T.V.RAO MD 6

HOW STERILIZATION WORKS

• Cell wall maintains integrity of cell

• When disrupted, cannot prevent cell from bursting due to

osmotic effects

• Cytoplasmic membrane contains cytoplasm and controls

passage of chemicals into and out of cell

• When damaged, cellular contents leak out

• Viral envelope responsible for attachment of virus to target cell

• Damage to envelope interrupts viral replication

• So…non enveloped viruses have greater tolerance of harsh

conditions

DR.T.V.RAO MD 7

METHODS • Physical

• Heat

• Filtration

• Irradiation

• Quarantine

• Chemical

• Choice of method depends on practical issues such as ease of use or material compatibility

• Proctoscope need not be as free of contamination as an artificial heart valve

• Cleaning of objects needed before attempt at sterilization

DR.T.V.RAO MD 8

• Strength of the killing agent

• Time that the agent has to act

• Temperature of environment

• rate of microbe death doubles with every 10˚C rise in temp.

• Type of microbe

• Environment around the area to be decontaminated

• Number of microbes to be killed

FACTORS INFLUENCING ABILITY TO

KILL MICROBES

DR.T.V.RAO MD 9

“IDEAL” STERILIZATION METHOD

• Highly efficacious • Rapidly active • Strong penetrability • Materials compatibility • Non-toxic • Organic material resistance • Adaptability • Monitoring capability • Cost-effective Schneider PM. Tappi J. 1994;77:115-119

DR.T.V.RAO MD 10

FACTORS THAT INFLUENCE EFFICACY

OF DISINFECTION/STERILIZATION

Contact time

Physico-chemical environment (e.g. pH)

3 Presence of organic material

4 Temperature

5 Type of microorganism

6 Number of microorganisms

7 Material composition

DR.T.V.RAO MD 11

burning method(incineration)

flowing steam disinfection

hot air drying method(烤箱) boiling water disinfection DR.T.V.RAO MD 12

DISINFECTION AND STERILIZATION

EH Spaulding believed that how an object will be disinfected depended on the object’s intended use.

CRITICAL - objects which enter normally sterile tissue or the vascular system or through which blood flows should be sterile.

SEMICRITICAL - objects that touch mucous membranes or skin that is not intact require a disinfection process (high-level disinfection[HLD]) that kills all microorganisms but high numbers of bacterial spores.

NONCRITICAL -objects that touch only intact skin require low-level disinfection.

DR.T.V.RAO MD 13

Endospores

Mycobacteria

Fungal Spores

Small Non-enveloped viruses (polio, rotavirus, rabies)

Vegetative Fungal Cells

Enveloped Viruses (Herpes, Hepatitis B, Hepatitis C, HIV)

Vegetative Bacteria

Most Resistant

Least Resistant

DR.T.V.RAO MD 14

SPORICIDAL AGENTS

• Glutaraldehyde

• Formaldehyde

• Other aldehydes

• Chlorine-releasing agents

• Iodine and iodophores

• Peroxygens

• Ethylene oxide

• P-Propiolactone

• A. D. RUSSELL, 1999. Bacterial Spores and Chemical Sporicidal Agents. CLINICAL MICROBIOLOGY REVIEWS Vol. 3, No. 2 p. 99-119 .

DR.T.V.RAO MD 15

DR.T.V.RAO MD 16

Physical Methods of Microbial Control:

Heat: Kills microorganisms by denaturing their enzymes and other proteins. Heat resistance varies widely among microbes.

Thermal Death Point (TDP): Lowest temperature at which

all of the microbes in a liquid suspension will be killed in ten

minutes.

Thermal Death Time (TDT): Minimal length of time in which

all bacteria will be killed at a given temperature.

Decimal Reduction Time (DRT): Time in minutes at which

90% of bacteria at a given temperature will be killed. Used in

canning industry.

DR.T.V.RAO MD 17

• 100 oC at 1 ATM

• 121 oC at 2 ATM (1 barr)

• 132 oC at 3 ATM (2 barr)

• 80 oC at 0.5 ATM (Mont Blanc)

• 70 oC at 0.35 ATM (Mont

Everest)

• 40 oC at 0.02 ATM

(Mechanical vacuum)

BOILING TEMPERATURE IS LINKED TO

PRESSURE

DR.T.V.RAO MD 18

BOILING • Kills vegetative cells of bacteria and fungi, protozoan

trophozoites, and most viruses within 10 minutes at sea

level

• Temperature cannot exceed 100ºC at sea level; steam

carries some heat away

• Boiling time is critical

• Water boils at lower temperatures at higher elevations;

requires longer boiling time

• Endospores, protozoan cysts, and some viruses can

survive boiling DR.T.V.RAO MD 19

PHYSICAL METHODS: HEAT

• Pasteurisation

• First used with milk: 72°C for 20 seconds

• Heating to 80°C for 1 minute will kill most vegetative organisms

• Examples: bed-pan washer, proctoscope

• Dry heat (hot air oven)

• used on waxes, oils (wet heat usually preferred)

• Incineration • the ultimate sterilization

• used for disposal of hospital waste

• Wet heat

• Boiling

• limited use as spores may be resistant, boilers may be misused

• Low temperature steam disinfection (75°C for 30 mins)

• Used for e.g. ventilator tubing

• Autoclaving

• High-temperature steam plus pressure (same principle as pressure cooker)

DR.T.V.RAO MD 20

MOIST HEAT

• Used to disinfect, sanitize, and sterilize

• Kills by denaturing proteins and destroying cytoplasmic

membranes

• More effective than dry heat; water better conductor of heat than

air

• Methods of microbial control using moist heat

• Boiling

• Autoclaving

• Pasteurization

• Ultrahigh-Temperature Sterilization

DR.T.V.RAO MD 21

MOIST HEAT

• Pasteurization

Definition: a process in which fluids are heated at temperatures below boiling point to kill pathogenic microorganisms in the vegetative state without altering the fluid’s palatability.

Conditions: 62℃, 30min or 71.7℃, 15sec

Significance: kills vegetative pathogens

Applications: milk, beer

DR.T.V.RAO MD 22

AUTOCLAVING • Pressure applied to boiling water prevents steam from escaping

• Boiling temperature increases as pressure increases

• Autoclave conditions – 121ºC, 15 psi, 15 minutes

DR.T.V.RAO MD 23

STRUCTURAL DIAGRAM OF AUTOCLAVES

DR.T.V.RAO MD 24

STEAM QUALITY IS IMPORTANT

Saturated steam

98% steam, 2% water vapor

Dry steam

Superheated

Wet steam

Supersaturated

DR.T.V.RAO MD 25

AUTOCLAVE

Figure 9.6b DR.T.V.RAO MD 26

Other Physical Methods of Microbial

Control:

Filtration: Removal of microbes by passage of a liquid or gas through a screen like material with small pores. Used to sterilize heat sensitive materials like vaccines, enzymes, antibiotics, and some culture media.

High Efficiency Particulate Air Filters (HEPA): Used in

operating rooms and burn units to remove bacteria from air.

Membrane Filters: Uniform pore size. Used in industry and

research. Different sizes:

0.22 and 0.45um Pores: Used to filter most bacteria. Don’t retain

spirochetes, mycoplasmas and viruses.

0.01 um Pores: Retain all viruses and some large proteins.

DR.T.V.RAO MD 27

Physical Methods of Microbial

Control: Radiation: Three types of radiation kill microbes:

1. Ionizing Radiation: Gamma rays, X rays, electron beams, or higher energy rays. Have short wavelengths (less than 1 nanometer).

Dislodge electrons from atoms and form ions.

Cause mutations in DNA and produce peroxides.

Used to sterilize pharmaceuticals and disposable medical supplies. Food industry is interested in using ionizing radiation.

Disadvantages: Penetrates human tissues. May cause genetic mutations in humans.

DR.T.V.RAO MD 28

FORMS OF RADIATION

DR.T.V.RAO MD 29

Physical Methods of Microbial

Control:

Radiation: Three types of radiation kill microbes:

Microwave Radiation: Wavelength ranges from 1 millimeter to 1 meter.

Heat is absorbed by water molecules.

May kill vegetative cells in moist foods.

Bacterial endospores, which do not contain water, are not damaged by microwave radiation.

Solid foods are unevenly penetrated by microwaves.

Trichinosis outbreaks have been associated with pork cooked in microwaves.

DR.T.V.RAO MD 30

• Mechanism

mechanically removes

microorganisms

• Application

sterilize materials

likely to be damaged

by heat

FILTRATION

DR.T.V.RAO MD 31

2007-5-26 32

滤菌过程

DR.T.V.RAO MD 32

HOW COMPLEX A ENDOSCOPE TO STERILIZE

DR.T.V.RAO MD 33

DR.T.V.RAO MD 34

• Major Categories

• Phenols

• Alcohols

• Halogens

• Oxidizing agents

• Surfactants

• Heavy Metals

• Aldehydes

• Gaseous Agents

• Antimicrobics

CHEMICAL METHODS OF MICROBIAL

CONTROL

DR.T.V.RAO MD 35

FACTORS INFLUENCING ANTIMICROBIAL

ACTIVITY

• the concentration and kind of an agent used

• the length of exposure to the agent

• the temperature at which the agent is used

• the number of microorganisms present

• the kinds of microorganisms present

• the nature of the material bearing the microorganism

DR.T.V.RAO MD 36

PHENOL AND PHENOLICS

• Intermediate- to low-level disinfectants

• Denature proteins and disrupt cell membranes

• Effective in presence of organic matter and remain

active for prolonged time

• Commonly used in health care settings, labs, and

homes (Lysol, triclosan)

• Have disagreeable odor and possible side effects

DR.T.V.RAO MD 37

• Intermediate-level

disinfectants

• Denature proteins and

disrupt cytoplasmic

membranes

• Evaporate rapidly – both

advantageous and

disadvantageous

• Swabbing of skin with 70%

ethanol prior to injection

ALCOHOLS

DR.T.V.RAO MD 38

ISOPROPYL ALCOHOL (70%)

ISOPROPYL ALCOHOL (70%)

• Powerful disinfectant and antiseptic • Mode of action: denatures proteins,

dissolves lipids and can lead to cell membrane disintegration

• Effectively kills bacteria and fungi • But does not inactivate spores!

DR.T.V.RAO MD 39

• Intermediate-level

antimicrobial chemicals

• Believed that they damage

enzymes via oxidation or by

denaturing them

• Iodine tablets, iodophores

(Betadine®), chlorine

treatment of drinking water,

bleach, chloramines in

wound dressings, and

bromine disinfection of hot

tubs

HALOGENS

DR.T.V.RAO MD 40

• Peroxides, ozone, and per acetic

acid kill by oxidation of microbial

enzymes

• High-level disinfectants and

antiseptics

• Hydrogen peroxide can disinfect

and sterilize surfaces of objects

• Ozone treatment of drinking

water

• Per acetic acid – effective

sporocide used to sterilize

equipment

OXIDIZING AGENTS

DR.T.V.RAO MD 41

SURFACTANTS • Surface active” chemicals that reduce surface tension of

solvents to make them more effective at dissolving solutes

• Soaps and detergents

• Soaps have hydrophilic and hydrophobic ends; good

degerming agents but not antimicrobial

• Detergents are positively charged organic surfactants

• Quats – colorless, tasteless, harmless to humans, and

antimicrobial; ideal for many medical and industrial application

• Low-level disinfectants

DR.T.V.RAO MD 42

HEAVY METALS • Ions are antimicrobial because they alter the 3-D shape of

proteins, inhibiting or eliminating their function

• Low-level bacteriostatic and fungistatic agents

• 1% silver nitrate to prevent blindness caused by

N. gonorrhoeae

• Thimerosal (mercury-containing compound) used to preserve

vaccines

• Copper controls algal growth in reservoirs, fish tanks, swimming

pools, and water storage tanks; interferes with chlorophyll

DR.T.V.RAO MD 43

• Denature proteins and

inactivate nucleic acids

• Glutaraldehyde both

disinfects (short exposure)

and sterilizes (long

exposure)

• Formalin used in

embalming and disinfection

of rooms and instruments

ALDEHYDES

DR.T.V.RAO MD 44

PROBLEMS WITH STERILITY

• Lack of understanding of risk/process

• physicians introducing new products (borrowed, samples)

• Multidose vials

• What is sterile vs not

• Lack of understanding of components of process

• MDs, technologists have less training than nurses (anaesthesiology, imaging, urology)

DR.T.V.RAO MD 45

GASEOUS AGENTS

• Ethylene oxide, propylene oxide, and beta-

propiolactone used in closed chambers to

sterilize items

• Denature proteins and DNA by cross-linking

functional groups

• Used in hospitals and dental offices

• Can be hazardous to people, often highly

explosive, extremely poisonous, and are

potentially carcinogenic

DR.T.V.RAO MD 46

• Yes.

• Plasmas are currently employed in many industries to accomplish both highly effective, and delicate sterilization.

• Not future technology! Plasmas are used today!

• But, how do they work?

CURRENT STERILIZATION

MEANS: PLASMAS?

DR.T.V.RAO MD 47

PLASMA STERILIZATION

• A plasma is a quasi-neutral collection of electrons, positive ions, and neutrals capable of collective behavior

• Positive ions = free radicals

• Plasma sterilization operates synergistically via three mechanisms:

• Free radicals interactions

• UV/VUV radioactive effects

• Volatilization

• Dead microorganisms = sterilization

DR.T.V.RAO MD 48

DISADVANTAGES OF PLASMA

STERILIZATION

• Weak penetrating power of the plasma species. Complications arise in:

• Presence of organic residue

• Packaging material

• Complex geometries

• Bulk sterilization of many devices

• Solutions: Introduce preferentially targeting UV/VUV radiation of proper wavelength

DR.T.V.RAO MD 49

CAN ENVIRONMENTAL CLEANING REDUCE

MRSA TRANSMISSION?

• Setting: ward with endemic MRSA, and

widespread environmental contamination

• Before-after study

• Cleaning time increased by 57 hours per week

• Responsibility for routine cleaning of shared

equipment delineated

• In 6 months post-intervention, number of MRSA

acquisitions decreased fro 30 to 3 per 6 months Rampling A JHI 2001;49:109 DR.T.V.RAO MD 50

• Audit and feedback

• New technology

• Hydrogen peroxide

vapour/gas

• UV room

decontamination?

antibacterial surface

coatings?

IMPROVING NON-CRITICAL

ITEM/ENVIRONMENT DISINFECTION

Otter ICHE 2009;30(6):574-7 DR.T.V.RAO MD 51

THE PROBLEM OF CJD AND TSES

• Creutzfeldt-Jakob syndrome and other transmissible spongiform

encephalopathies caused by highly resistant proteinaceous particles,

prions

• can survive 3 years of environmental exposure and are unusually

resistant to conventional decontamination methods

• Iatrogenic CJD documented in three circumstances

• use of contaminated medical equipment (2 cases)

• use of extracted pituitary hormones (> 130 cases)

• implantation of contaminated grafts from humans (cornea, 3 cases; dura

mater, > 110 cases)

DR.T.V.RAO MD 52

INACTIVATION OF PRIONS

• Steam sterilization with NaOH

• Alkaline cleaner (pH 2.2, 1 hr 23°C)

• Copper plus peracetic acid

• Vapourized hydrogen peroxide (Sterrad NX)

Yan ICHE 2004;25:280, Fichet Lancet 2004;384:251, Baier JHI 2004;57:80,

Lemmer J Gen Virol 2004;85:3805; Roger-Kreuz, ICHE 2009;30(8):769-77

Lehman Hosp Infect. 2009;72(4):342-50; DR.T.V.RAO MD 53

WHAT IS AN INDICATOR OR

STERILISATION CONTROL ?

• On paper

• Self -contained

• Sealed ampulla (spores + broth)

• Spores suspension

• Tube witness (point of fusion)

It is a device conceived to verify

if the process operated as expected

DR.T.V.RAO MD 54

VALIDATION OF BIOLOGICAL

INDICATORS

• The reality :

• We do not use the most resistant organisms

• The predictive behaviour is generally linear only for one process

• Manufacturers seldom use more “practical” strains (read : “less linear” strains for more economical, inoffensive, self resistance and stability)

• There is no such thing as a “universal biological indicator”

• The choice of any particular strain is therefore a manner of arbitrary choice

DR.T.V.RAO MD 55

3M RAPID INDICATOR

DR.T.V.RAO MD 56

QUANTIFYING

STERILIZATION EFFICACY

•

•

i.e. Time required for the

microbial population to be reduced

to one decimal

DR.T.V.RAO MD 57

• Little evidence that

extensive use of

products containing

antiseptic and

disinfecting chemicals

adds to human or

animal health

• The use of such

products promotes the

development of

resistant microbes

EXCESSIVE USE OF CHEMICALS CAN

CREATE RESISTANT MICROBES ???

DR.T.V.RAO MD 58

• Avoid cleanrooms when ill

• Frequent bathing and

shampooing

• Avoid cosmetics such as

face powder, hair sprays,

perfumes and aftershave

• Clothing should be clean,

nonfrayed and nonlinting

• Avoid smoking

STERILIZATION IS SUCCESSFUL

WITH PERSONNEL: HYGIENE

DR.T.V.RAO MD 59

WHO / WHAT IS IMPORTANT IN PREVENTION OF

INFECTIONS

WE ARE ALL IMPORTANT

DR.T.V.RAO MD 62

• Programme created by Dr.T.V.Rao MD for

Medical and Paramedical Professionals in

the Developing World

• Email

• [email protected]