The document discusses sterilization and disinfection methods used in hospitals. It begins by defining key terms like sterilization, disinfection, cleaning, and antisepsis. It then describes various chemical and physical methods used for disinfection and sterilization of medical equipment, including steam, ethylene oxide, hydrogen peroxide gas plasma, and peracetic acid. Factors that can affect sterilization effectiveness, like cleaning and device design, are also covered. The document emphasizes that proper cleaning is required before disinfection or sterilization and that instrument classification guides appropriate processing method.

1. 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

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

3.  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

4.  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)

6. 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

7.  Cleaning
 Disinfection
 Sterilization

8.  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

9.  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

10.  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 %)

11.  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

12.  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

13.  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

14.  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

15.  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

16.  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

17.  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

18.  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

19.  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

20.  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

21.  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

23.  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

24.  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

25.  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

26.  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

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

29.  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

30.  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)

31.  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

32.  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

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

34.  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

35.  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.

36.  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

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

38.  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