Principles of reprocessing: Sterilisation,disinfection &

cleansing Department of Infection Control and Hospital Epidemiology

Prof. Dr. Elisabeth Presterl MBA DTHM (London)

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PLEASE NOTE AND RESPECT

• Photography, filming or streaming of the presentations during the course ARE

NOT ALLOWED due to the copyrights and the European data protection regulation

• Handouts are provided for personal purposes. Distribution of handouts is not

allowed

• Please put your mobiles into silent mode (and please call back in the breaks if

possible)

• Please take all your belongings after the end of the course with you (including all

dechets)

• During examination the use of mobiles and handouts is not allowed (actually you

will not need them)

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Prevention of healthcare-associated infections (HAI)

• „Asepsis“

• „Non-contamination“

• Barriers – distance – tools (e.g. sterile gloves, pincers etc.)

• „Antisepsis“ – „decontamination“, „reprocessing“

• Desinfection

• Sterilization

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Measures to avoid

microbial contamination

Antisepsis Asepsis

Killing of

microorganisms

Sterilisation

Desinfection

Cleaning

e.g. sterile drapes,

instruments,clean medical

devices and tools, hand

hygiene, etc. - these

fomites are decontaminated

to avoid any risk of

contamination and transfer

of microbes andn infection

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Principles of hygiene

• KEEP CLEAN (STERILE)

• SEPERATE CLEAN FROM UNCLEAN

• Rooms

• Material

• People

• FOR OPTIMUM REPROCESSING USE (technical/automated) PROCEDURE WHERE YOU

CAN CONTROL (measure and document) THE PARAMETERS (temperature, time,

pressure, moisture etc.)

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Bacterial killing curves

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Presterl et al; JAC 2007 - Effects of alcohols, povidone-iodine and hydrogen peroxide

on biofilms of Staphylococcus epidermidis

Phases of bacterial killing:

• Lag phase

• Excelerating phase

• Exponential (log) phase

• Retardation phase

• Stationary phase

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Sterilisation

• Sterility is the abscence of microorganisms and spores (European Pharmacopoea)

• Sterilisation is defined as the killing and/or removal of all viable microorganisms

and spores

• This absolute abscence of microorganisms is mandatory for all substances,

formulations and devices which will be in contact with the bloodstream, sterile

tissue, organs and wounds of humans

• For sterilisation the obligatory reduction of microorganisms is > (greater than) 6

log counts = 99,9999% x2 (2 times) = > 12 log; 99,9999999999% (safety

assurence level SAL)

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Principles • Devices and fomites have to be absolutely free*) from infectious agents of any

type

• Note: The proof of sterility ist not possible on the sterilized item/device/fomite !

• *) Convention: The probability of the survival of a SINGLE microorgism must not

be greater than 1 in 1000 000.

• *) The benchmark for thermal sterilisation is the most resistant, microbial spores

of Bacillus anthracis or Clostridium tetani, thus Bacillus stearothermophilus

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Desinfection

• Disinfection is defined as the killing of all pathogenic microorganisms. The

number of the pathogenic microorganisms on fomites, surfaces and devices must

be reduced to that exent to prevent an infection (transmission)

• For disinfection the obligatory reduction of microorganisms is > (greater than) 5

log counts = 99,999%

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Cleansing

• What is cleasing:

o To clean

o To remove visible dirt?

o To remove mechanically microorganisms?

• NOTE: Any removal of dirt is connected with significant microbial reduction

o Crude cleansing: Microbial reduction of 1 - 2 log counts (90 - 99%)

o In-depth manual cleansing: reduction by 2 - 3 log counts (99 - 99,9%)

o Machine-made cleansing: by 4 - 6 log counts (99,99 - 99,9999%)

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Stepwise strategy for desinfection and sterilisation of medical fomites

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Principles of reprocessing

• There is no general reprocessing protocol („NO one-for-all“!)

• Reprocessing must be defined and validated for each medical fomite or device, in

particular for critical and semicritical medical devices (European medical device

regulation)

• Reprocessing protocols are based on

o Stability to temperature (Thermal reprocessing)

o Type of contamination (microorganisms)

o Extent of microbial contamination

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Resistance of microorganisms against reprocessing procedures

resistant

susceptible

Prions

Spores (C. perfringens)

Mycobacteria (M. tuberculosis)

Viruses without envelope

(Poliovirus, Coxsackievirus)

Viable bacteria (P. aeruginosa, S. aureus)

Enveloped viruses (HSV, CMV, RSV, HIV)

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Classification of microbial sensitivity for reprocessing

• Group A: Viable bacteria, fungi

• Group B: Viruses

• Group C: Spores of Bacillus anthracis

• Group D: Spores of Clostridium perfringens and Clostridium tetani

Sterilisation

Groups A-D

Desinfection

Groups A-B

Overall principle

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Classification of medical instruments, devices and products

Critical Invasion into sterile tissue

or the bloodstream

Vasculare catheters,

surgical instruments

Sterilisation

Semi-critical Contact with mucosal

surfaces and wounds

(including open skin lesions)

Endoscopes, respiration

equipment

Sterilisation /

disinfection

Uncritical Contact with intact skin

surface

Blood pressure meter,

bed pan

Desinfection /

cleansing

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Sterilisation – techniques and procedures

• Physical sterilisation techniques

• High temperature moist steam sterilisation

• High temperature dry steam sterilisation

• Filtration

• Physicochemical techniques (low temperature sterilisation techniques)

• Ethylene oxide sterilisation

• Formaldehyde sterilisation

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High temperature sterilisation

• Steam sterilisation:

o Sterilisation with high-temperature, high-pressure and saturated steam in steam

sterilizers

o Common protocols: 121°C plus 2 bar pressure, alternatetively 34°C plus 3 bar

pressure

o Most efficient (safe, quick) sterilisation procedure („gold standard“)

• Dry heat sterilisation:

o Sterilisation using dry heat only

o Important for use: care for adequate heat conduction, convection and heat contact

transfer plus appropriate heat tolerability of the fomites

o Common protocol: 180°C for at least 30 minutes (excluding heating and cooling

times)

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Physical sterilisation procedures

1. Steam = moist heat

o Saturated = The amount of air is <10%

o Under pressure to in increase temperature

2. Hot air = dry heat

o Common temperatures: 180°C for 30-60 minutes, or 200°C for 10 minutes

3. Filtration

o Sterilisation and removal of microbial debris (including endotoxins)

o For fluids (e.g. sterile saline etc.)

T (°C) P (bar) t (min)

121 2 15

134 3 3

145 4 1

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Advantages of high temperature sterilisation

• Fast impact

• Broad spectrum for use

• Low impact of environmental conditions

• Reliably controlling of working parameters (temperature, killing time)

• No toxic remnant in the sterile goods (ecology)

• Steam or heat are re-usable (economy)

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Principle of steam sterilisation

• The heat capacity of steam is higher than that of air.

• Principle: Condensation (cooling) of steam at 100°C to water at 99°C produces

2260 times as much energy than cooling of the identical mass of air from 100°C

to 99°C.

• Moist heat kills microorganisms much better than dry heat.

• Steam sterilisation is much more reliable than dry heat sterilisation (and shorter)

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Mandatory precondition for steam sterilisation

• STEAM must reach ALL SURFACES of the goods to be sterilized to condensate on

these surfaces and kill the microorganisms

• THUS: ALL AIR within the goods to be sterilized (particularly from hollow bodies or

porous materials) MUST BE REMOVED!

• HOW: Evacuate all air by prior (air) evaucation step

• Mandatory: VALIDATE function (see next talk)

• = a steam sterilizer is a highly sophisticated and high-tec instrument!

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Physicochemical sterilisation techniques

• Comparatively low temperature sterilisation procedures for heat-sensible goods

• Ethylene oxide (EO steam) sterilisation

• Common protocols: (gas) sterilisation at 37°C for 250 minutes or at 60° for 20 minutes

• HAZARDOUS: Toxic, teratogenic, mutagenic, carcinogenic, explosive

• Removal of residual EO requires aeration time up to 16 hours (total circle time = 72

hours)

• Formaldehyde – steam sterilisation

• Mixture of 2-3% formaldehyd and steam

• Common protocol: (gas) sterilisation at 60-70°C for 60 minutes (NOT SPORICIDAL)

• HAZARDOUS: Toxic, teratogenic, mutagenic, carcinogenic – NOT explosive

• Easy removal from goods - no aeration time

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Which sterilisation technique for which medical goods?

Metal, ceramics, glas, textiles

• No convection or transfer of

high temperature into the

materials

• damage by pressure (changes)

• steam cannot penetrate into

the goods (e.g. oils)

“Gold standard”

Powder, hydrophobic fluids

(oil, fat)

• damage by high temperature (>

180°C)

Validation not really possible

(do not use in medical

practice)

Formaldhyde steam

sterilisation

Metal, ceramics, glas, textiles;

Temperature tolerability limit

ca 60°C

• See steam sterilisation

Only for sterile goods which

does not tolerate high

temperature and pressure

Ethylene oxide sterilisation

See above, temperature

tolerability ca 45°C

• Damage by EO

Only for sterile goods which

does not tolerate high

temperature and pressure

H2O

2-Plasma

(not permitted in Austria,

with a single exception)

Heat labile goods

• Damage by H2O

2-Plasma

• Problems with fences and

shadowing by metal

components

Only for heat labile goods

BEWARE: Remnants of soaps,

detergents, salts on the

goods to be sterilized impair

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Sterilisation of goods contaminated with prions

• Prion infections: Creutzfeld-Jakob‘s disease (CJD), variant CJD (vCJD), mad cow

disease

• Prions are proteins resistant to desinfection and routine sterilisation

• PIVOTAL: risk assessment of the patients, deep cleansing, use cleansing solution

with highly alkaline ph (11)

• Sterilisation technique and procedure according to national and international

regulations

• Generally: USE SINGLE USE materials and instruments gilt: nicht wieder verwenden

• Sterilisation: High temperature steam sterilisation at 134°C for 18 Minuten

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Important prerequisites for sterile goods - packaging

• Packaging material must not inhibit the sterilisation process (steam and heat must

penetrate easily)

• Packaging material must ensure sterility for a certified period

• Removal and handling of the sterile contents must be easy to avoid contmination

• Types of packaging:

o Solid containers (Aluminium, steel)

o Transparent paper-foil combination wraps

o Sterilisation paper wrap

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Expiry date of sterile goods – recommendations

Single wrapping 48 hours 6 months

Double wrapping 6 weeks 6 months

Solid container 6 months

Industrial wrapping

(industrial producers)

6 months or according to the

producer‘s declaration

* Protected = in closed closets or rooms with a heating ventilation and air conditioning systems to be protected against dust and dampness

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Pitfalls and errors durch sterilisation

1. Faulty pre-requisite cleaning

2. Wrong type of sterilisation technique

3. Wrong type of sterilisation good material

4. Wrong type of wrapping or defective

5. Defect sterilizer or errors in operating the sterilizers (e.g. because of missing

traininung and education)

6. Faulty control of the function of the sterilizers (Automatic protocol)

7. Faulty labelling of the sterile goods

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Disinfection – techniques and procedures

•

o Thermal - heat

o Radiation (UV-rays at wavelength of 254 nm)

• Alcohols

o Aldehydes

o Phenoles

o Halogene

o Peroxide releasing agents

o Heavy metals

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Physical disinfection techniques

•

o Burning, annealing, flaming

•

o Use boiling water (85-95°C) with the addition of 0,5% sodium carbonate for 3

minutes (groups A + B), 15 minutes )or for 15 minutes (groups A+B+C)

o (e.g. professional dish washers, bed pan disinfectors)

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Physical disinfection techniques

•

o Steam disinfection using saturated steam at 100°C

o 5 minutes for groups A+B or 15 minutes for groups A+B+C; (e.g. medical

waste)

o Physicochemical disinfection at 60°C for 10 minutes for A+B (e.g. narcosis masks,

tubes, endoscopes)

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Physical disinfection techniques

• Pasteurisation

o Short heating up to 65-150°C

• Tyndallisation (Tyndall‘s effect)

• Principle:

o Step 1: Heating up to 70-80°C to kill all viable bacteria

o Step 2: Let bacteria sporulate

o Step 3: Re-heating: sporulated bacteria are killed

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Chemical disinfection Ethanol, iso-Propanol, n-Propanol (Alcohols)

• Indications:

o Hand disinfection

o Disinfection of instruments

o Disinfection of small surfaces

• Advantage:

o Rapid action

o Slow protein

o Not inhibited by proteins

• Disadvantage:

o Not sporicidal

o Virucidal against viruses without envelop at concentrations > 70%

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Inhibition by proteins

Cell membrane +

Transporters

Periplasmatic space

Peptidoglycans

Porin

Braun lipoproteines

Outer membrane

Lipid A plus

Oligosaccharide chain

D D

D

D

D

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Chemical disinfection Formaldehyd (= 35-40% FO solution in water), glutaraldehyde (Aldehydes)

• Indications:

o Disinfection of large surfaces (e.g. operation rooms)

o Disinfection of instruments

• Advantage:

o Broad spectrum (Disinfection of groups A+B+C(+D) (=spores!) at long exposure times

and high temperature in disinfection maschines)

o Potentially inhibited by proteins (concentration dependant)

• Disadvantage:

o Allergy

o Carcinogenic

o Note (occupational safety): MAC-value: 0.6 mg/m3 air

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Chemical disinfection Diphenylderivates: Chlorhexidin, octenidin (phenols)

• Indication:

o Gram-positive microorganisms, enveloped viruses

• Advantage

o Disinfection of mucosal membranes, skin

o Only marginally inhibited by proteins

• Disadvantage:

o No action against spores, HBV, viruses without envelope, mycobacteria

o Potentially carcingenic, toxic

o Resistance possible

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Chemical disinfection Chlorine, iodine, bromide (halogen releasing agents)

• Indication:

o Disinfection for groups Gruppe A+B(+C)

o Disinfection of drinking, bathing and waste water

• Advantage:

o Widely used (PVP-iodine)

• Disadvantage:

o No action against spores

o Potentially carcinogenic, aggressive

o Inhibited by proteins

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Chemical disinfection Ozone (active oxygen), potassium permanganate, hydrogen peroxide (H2O2), oxidant releasers)

• Indication:

o Disinfection of instruments

o Disinfection of large surfaces (floors, walls)

o Wounds and mucosal membranes (obsolete)

• Advantage:

o Use for water disinfection (plus chlorine)

• Disadvantage:

o Corrosive

o Inhibited by proteins !!! – Mandatory pre-cleansing removing dirt and proteins

o Explosive

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Chemical disinfection Heavy metals (Mercury, mercurochrome)

• Indication:

o Wound disinfection (obsolete)

• Advantage:

o Well known – cheap

• Disadvantage:

o Toxic

o Inhibited by proteins

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Chemical disinfectants – general disadvantage

• Reduced action by bubbles and gross dirt

• dependant on the agent (Spores, viruses)

• Concentration dependant -

•

• Temperature and pH-dependant

•

• Inhibition by proteins:

Halogens

Oxidants

Heavy metals

(Tensides)

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Hygienic requirement to surface disinfection

Use moist or wet wiping with clean (!) utensils

No spraying! (Beware: inhalation! Occupational hazard)

Use alcohols only for small surfaces in the patient environment (rapid action, no

remnants) – Beware: Combustion (Vapours or still wet wipes)

Adhere to correct dosing of comercially available disinfectants according to the

instruction sheet (Education, training and audit of the personel doing the

disinfection)

Strictly adhere to the exposure times (Instruction sheet, concentrations)

Only use products which are reliably tested by an appropriate institution e.g. VAH

(D) https://vah-online.de/de/vah-liste , EPA (US)

Make a clear and concise guidance document for cleansing and disinfection in

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Guidance documents for reprocessing

• Reprocessing of semi-critical or critical medical devices or fomites are part of the

operating instruction and must be executed (BEWARE: deviations may lead to

malfunction and/or loss of waranty

• For uncritital fomites and surfaces a general guidance document about the use of

disinfectants, the choice of disinfectants and the exposure times are necessary for the

adequate operation.

o Basic informations

o Type of disfectant

o When to use, how often

o Type of application

o Necessary tools for application

o Accountable person(s)

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Differential considerations

• Hand hygiene (disinfection)

• Surfaces (Tables, fomites, walls …)

• Instruments

• Medical devices

• Furniture, computers

• Floors

• Routinely (e.g. 1x/d) vs. when necessary

• Small vs. large surfaces

• Cleansing sufficient or plus disinfection

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Guidance document for cleansing and disinfection of surfaces and fomites https://www.meduniwien.ac.at/hp/krankenhaushygiene/hygienemappe/hygienerichtlinien/

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QUIZ: Sterilisation - disinfection - cleansing

Coronary catheter

Larynx mask

Aspiration set for

lumar puncture

Urinary catheter

(single use)

Floor at ICU

Respiration tube

Bed pan

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Coronary catheter critical Sterilisation

Larynx mask Semi-critical Disinfection

Aspiration set for

lumar puncture

critical Sterilisation

Urinary catheter

(single use)

critical (must be sterile) –

discard after use

Floor at ICU uncritical Cleansing

Respiration tube Semi-critical Disinfection

Bed pan Semi-critical Disinfection

QUIZ: Sterilisation - disinfection - cleansing

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