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Moderator: Dr.K.S.Dhillon
HOD, Dept. of Gen. Surgery
Max super speciality Hospital,
Mohali, Punjab
Presenter : Dr. Asif Mian Ansari
DNB resident
Dept. of General Surgery
Max hospital, Mohali

 Terminology
 Introduction
 Levels of disinfection
 Types of items/devices
 Common methods of cleaning, disinfection & sterilization
 Factors affecting steriization

 Sterilization:
 Destroys all forms of microbial life + bacterial spores
 Disinfection:
 Destroys many or all pathogenic microorganisms- except bacterial
spores
 Cleaning:
 Removal of visible soil from objects and surfaces
 Antisepsis:
 Prevent sepsis (infection) by killing infectious microorganisms
 Sanitize:
 Reduce the number of micoorganisms

 Surgical/medical procedure  instrument contact with
patient’s tissues  risk of pathogen transfer
 Failure to sterilize/disinfect instrument  pathogen entry to
patient or transfer of infection
 Sterilization is not required for all instruments as Disinfection
or cleaning is sufficient for them
 Instruments classification according to risk of infection
(Spaulding classification)

Sterilisation & disinfection

Resistance to biocides
MOST RESISTANT
LEAST RESISTANT
Bacterial spores Sterilization
Mycobacteria High level disinfection
Non-lipid or small virus (poliovirus) Intermediate disinfection
Fungi Low level disinfection
Lipid or medium sized virus (HIV)
Vegetative bacteria

 Cleaning
 Disinfection
 Sterilization

 Removal of foreign material (soil/organic material)
 Water with detergents
 Enzymatic methods
 Mandatory before disinfection or sterilization
 Friction : rubbing/scrubbing the soiled area with a brush
 Fluidics : fluids under pressure is used to remove soil / debris
 Neutral or near neutral pH solution with detergent is used
 Enzymes : proteases/lipases/amylases some times added to
neutral pH solutions

 Destruction of many or all pathogenic microorganisms -
except bacterial spores
 Required for non-critical and semi-critical items
 Chemicals or combination of chemicals registered with EPA
(environmental protection agency) or FDA (food and drug
administration)
 Used in standard concentration

 Ethyle alcohol and iso-propyle alcohol
 Kill all microbes except bacterial spores
 MOA: protein denaturation
 Ethyle alcohol (30 – 100%): bactericidal & virucidal in 10-15 sec
including tubercle bacilli
 Iso propyle alcohol is more potent and used in less concentrations
 Uses : disinfection of thermometers, stethoscopes, USG probes,
medication preparation areas
 Limitations : damage to shellac mountings of lens, tend to harder
rubber tubings after prolonged use, damage tonometer tips. It is
flammable
 Chlorhexidine (2.5 %) + alcohol combination (70 %)

 Sodium hypochlorite (5.25 - 6.15% ) : household bleech
 Remove dried or fixed organisms and biofilms from surfaces
 Superoxide water : hypochlorous acid + chlorine
 Others : chlorine dioxide, sodium dichloroisocyanurate, and
chloramine-T
 MOA : active component is HOCl > OCl-
 oxidation of sulfhydryl enzymes and amino acids
 inhibition of protein synthesis
 decreased oxygen uptake
 decreased ATP production
 depressed DNA synthesis

 Uses:
 A 1:10–1:100 dilution of 5.25%–6.15% sodium hypochlorite solution
for decontaminating blood spills
 Chlorine tablets have been used as the disinfectant of water
 Adverse effects:
 Can produce ocular irritation or oropharyngeal, esophageal, and
gastric burns
 Corrosiveness to metals
 Carcinogenic : chloromethyl and trihalomethane

 Present in liquid and gaseous states
 Available as formalin (37% formaldehyde)
 MOA :
 alkylating the amino and sulfhydral groups of proteins and ring nitrogen
atoms of purine bases
 2 % formalin – viruricidal
 4 % formalin for 2 minutes – tuberculocidal
 Uses :
 High level of disinfection
 preserve anatomic specimens
 Prepare viral vaccines (poliovirus and influenza)
 Embalming agent

 Aqueous solutions of glutaraldehyde are acidic  not sporicidal
 Activated solution (made alkaline) at pH 7.5–8.5  sporicidal
 Activated solution half life is 14 days
 MOA : Alkylation of sulfhydryl, hydroxyl, carboxyl groups, which
alters RNA, DNA, and protein synthesis
 Minimum effective concentration  1.0%–1.5%
 >2% glutaraldehyde solution as a high-level disinfectant
 Uses :
 As a high-level disinfectant for endoscopes, spirometry tubing,
dialyzers, transducers, anesthesia and respiratory therapy equipments

 As a high-level disinfectant for reuse of laparoscopic disposable
plastic trocars
 Noncorrosive to metal
 Does not damage lensed instruments, rubber or plastics
 Too toxic and expensive  Should not be used for cleaning
noncritical surfaces

 FDA listed it as a sterilant & high-level disinfectant
 MOA : producing destructive hydroxyl free radicals which
attacks membrane lipids, DNA, and other essential cell
components & destroys cell
 Uses :
 3% to 6% for disinfecting soft contact lenses, tonometer, biprisms,
ventilators, fabrics and endoscopes

 Iodine solutions or tinctures used by health professionals
primarily as antiseptics or disinfectant
 MOA : iodophors  Iodine  penetrate the cell wall of
microorganisms quickly  disruption of protein and nucleic
acid
 Povidone iodine
 Uses :
 As an antiseptic
 As a disinfectant for blood culture bottles, thermometers &
endoscopes

 It contains 0.55% 1,2-benzenedicarboxaldehyde (OPA)
 Is a high-level disinfectant
 MOA :
 Interact with amino acids & proteins
 Kills spores by blocking the spore germination process
 Advantages over glutaraldehyde : Not irritant to the eyes and
nasal, has a barely perceptible odor and requires no activation
 Disadvantage of OPA is that it stains proteins gray including
skin

 Peracetic acid is characterized by rapid action against all
microorganisms
 It is an oxidizing agent
 Uses :
 chemically sterilize medical, surgical, and dental instruments
 Peracitic acid with hydrogen peroxide (0.23 % with 7.35%) kills all
microorganisms except bacterial spores within 20 minutes and used
for disinfecting hemodialyzers

 Two phenol derivatives commonly used as hospital
disinfectants  ortho-phenylphenol and ortho-benzyl-para-
chlorophenol
 MOA : In high concentrations, phenol acts as a protoplasmic
poison, penetrating and disrupting the cell wall
 Uses : As disinfectants for bedside tables, bedrails, and
laboratory surfaces and noncritical medical devices

 Fungicidal, bactericidal, and virucidal against lipophilic
(enveloped) viruses but not sporicidal, tuberculocidal or
virucidal against hydrophilic (nonenveloped) viruses
 MOA : Inactivation of energy-producing enzymes
 Uses : environmental sanitation of noncritical surfaces, such
as floors, furniture, and walls
 Benzalkonium chloride

 Sterilization destroys all microorganisms on the surface of an
article
 All critical items require sterilization before use
 Most medical and surgical devices are heat stable and undergo
heat sterilization
 Now, increase in medical devices and instruments made of
materials that are heat labile & require low-temperature
sterilization

 Steam under pressure  most widely used
 Nontoxic, inexpensive, rapidly microbicidal & sporicidal
 Principle : four parameters : steam, pressure, temperature, and
time
 Two common steam-sterilizing temperatures
 121°C + 15 psi for 30 minutes
 132°C + 30 psi for 4 minutes
 The two basic types of steam sterilizers (autoclaves)
 Gravity displacement autoclave
 High-speed prevacuum sterilizer

 The effectiveness of steam sterilization is monitored with a
biological indicator containing spores of Geobacillus
stearothermophilus
 MOA : irreversible coagulation and denaturation of enzymes
and structural proteins
 Uses : used whenever possible on all critical and semicritical
items that are heat and moisture resistant

 Sterilization of an unwrapped objects to allow for rapid
penetration of steam
 In gravity displacement or prevacuum autoclave non porous
items to be kept at 132°C for 3 minutes
 For porous items duration is 10 & 4 minutes respectively in In
gravity displacement & prevacuum autoclave
 Used when items need rapidly to be sterilized
 Risk of contamination is more during transportation

 Used for Heat & moisture sensitive items
 Temperature < 60°C

 Colorless, flammable and explosive gas
 Requirements :
 gas concentration (450 to 1200 mg/l);
 temperature (37 to 63°C);
 relative humidity (40 to 80%)
 exposure time (1 to 6 hours)
 ETO sterilization cycle consists of five stages : preconditioning
and humidification, gas introduction, exposure, evacuation,
and air washes
 MOA: alkylation of protein, DNA, and RNA

 Uses: ETO is used to sterilize moisture or heat sensitive critical
items and sometimes semicritical items
 Disadvantage:
 lengthy cycle time
 Cost
 potential hazards to patients and staff (acute inhalation causes
irritation of mucus membranes & Chronic inhalation has been linked
to the formation of cataracts, cognitive impairment, neurologic
dysfunction, and disabling polyneuropathies and cancers)

 Gas plasma is the fourth state of matter
 Charged gas particles
 Hydrogen Peroxide Gas vapors at 6 mg/l concentration is diffused
in an evacuated chamber.An electrical field created by a radio
frequency is applied to the chamber to create a gas plasma and
inactivation of microbes starts
 Takes around 50 minutes (28-38 minutes in newest version)
 MOA: free radicals injury and hydrogen peroxide gas activity
 Indicator : Bacillus atrophaeus spores
 Use : plastics, electrical devices, and corrosion-susceptible metal
alloys

 Highly biocidal oxidizer that maintains its efficacy in the
presence of organic soil
 This microprocessor-controlled, low-temperature (50°C)
sterilization method is commonly used for sterilization of
endoscopes, arthroscopes and bronchoscopes
 35% peracetic acid, and an anticorrosive agent are supplied in
a single-dose container  container is punctured at the time
of use, immediately prior to closing the lid and initiating the
cycle
 Indicator : G. stearothermophilus spore strips

 MOA: oxidize & denatures proteins, disrupts cell wall
permeability
 Uses:
 endoscopes, bronchoscopes sterilizaton
 Peracitic acid with hydrogen peroxide : disinfection of hemodialysers

 Ionizing Radiation:
 by cobalt 60 gamma rays or electron accelerators
 Dry-Heat Sterilizers:
 Only for materials that might be damaged by moist heat or that are
impenetrable to moist heat (e.g., powders, petroleum products,
sharp instruments)
 170°C for 60 minutes, 160°C for 120 minutes, and 150°C for 150
minutes.
 B. atrophaeus spores used as indicator

 Performic Acid: fast-acting sporicide that is used in an
automated endoscope reprocessing system. Not currently
FDA cleared.
 Filtration: used to remove bacteria from thermolabile fluids
that cannot be purified by any other means. Standard
membrane pore size is 0.22 μm. Not currently FDA cleared.
 Microwave: used for disinfection of soft contact lenses, dental
instruments, dentures, milk etc.

 Ozone : ozone as the sterilant, was cleared by FDA in August
2003. duration of cycle is about 4 h and 15 m, and it occurs at
30-35°C. Can be used for stainless steel, titanium, anodized
aluminum, ceramic, glass, silica, PVC,Teflon, silicone,
polypropylene, polyethylene and acrylic
 Formaldehyde Steam: A formaldehyde concentration of 8-16
mg/l is generated at an operating temperature of 70-75°C.
Initial vacuum  steam admission  series of pulses of
formaldehyde gas  followed by steam & air flushing pulses.
Not FDA cleared

 Cleaning
 Bioburden
 Pathogen type
 Protein & salt
 Biofilm accumulation
 Restricted flow
 Device design and construction

 Not all instruments need sterilization
 In some situation semi-critical items may work as critical
items  should be sterilized
 Autoclaving & ETO are most widely used methods
 Cleaning is essential part before disinfection or sterilization

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