3. Noha Tharwat Abou El-khier
Ass. Prof. Medical Microbiology &
Immunology
Official Email : nohat75@yahoo.com
Mobile: 01020100764
Academic Hours : Monday (11-1 pm)
4. Content of lecture
1
•Physical methods of Sterilization/disinfection
2
•Chemical methods of Sterilization/disinfection
3
•Spaulding classification system
5. Learning Outcomes
Define the terms; Sterilization, Disinfection, Disinfectants, Antiseptic
Recognize the factors Influencing efficacy of Sterilant/Disinfectant
Identify the types of microorganisms that are most resistant and least resistant to sterilization methods.
Enumerate and describe different physical methods of sterilization/ disinfection.
Enumerate and describe different chemical methods of sterilization/ disinfection.
Define and describe Spaulding classification system
At the end of the lecture, the students should be able to:
6. Case scenario
In an operation room, during an Orthopaedic
surgery, one of the surgical instruments
accidentally dropped on the theater floor.
Unexperienced nurse picked it and soaked it in
cidex solution (glutaraldehyde) only for one
minute then gave it to the surgeon. The
patient developed postoperative surgical site
infection.
9. • A complex subject related to the entire process, including cleaning 1st, followed
by disinfection, and/ or sterilization.
Decontamination
• all healthcare facilities must have a comprehensive decontamination policy to
ensure that all re-usable medical items are adequately cleaned, disinfected,
and/or sterilized before use.
Decontamination policy
• All medical devices that are reprocessed must undergo a rigorous cleaning for
physical removal of organic matter such as blood and body fluids prior to
disinfection and/ or sterilization. It is either manual or automatic cleaning.
Cleaning
10. Factors Influencing Efficacy of
Sterilant/Disinfectant
1- Organism load
2- Nature of organisms
3- Concentration of the chemical agent and temperature of the physical
agent
4- Nature of the sterilant/disinfectant
5- Duration of exposure
6- pH
7- Biofilm formation
11. The decreasing order of resistance of microorganisms
to disinfectant or sterilizing agents
• Prions
• Spores
• Mycobacteria
• Non enveloped virus
• Fungi
• Vegetative bacteria
• Enveloped virus
14. • Scalpels, needles, mouth of culture tube, glass slide
Flaming
• Dead bodies, contaminated disposable items
Incineration
Hot air oven
15. Hot air oven
– Electrically heated
– Thermostat
– Fan
Holding time:
– 160° C 2hs
– 180° C 1h
Used for:
– Glasses
– Metals
– Dry material in sealed container: oil,
powder
Precautions
Glass: good quality, dry
Object put while oven is cold
Holding time: calculated?
Oven left to cool
16.
17. • 63°C for 30 min rapid cooling
• Kill non-sporing bact. (bovine TB)
Pasteurization of milk
• Used for disinfection of serum, body fluids, and
vaccines
• 60°C for 1h (vaccine path)(non sporing bacteria)
• Temp. immunizing power
Water bath
18.
19.
20. • Immediate use (flash) sterilization system (IUSS):
• Flash sterilization used to process a critical item (e.g. surgical
instrument) which has become accidentally contaminated
during a surgical procedure and there is a need to be sterilized
in a hurry.
• They operate at 134°C for 3 min for nonporous items or 10 min
for porous material in a gravity-displacement autoclave.
21. • Uses of autoclave:
Autoclave is useful for surgical instruments and culture media and those
materials which cannot withstand the higher temperature of hot air oven or
media containing water that cannot be sterilized by dry heat.
• Sterilization control:
• Biological indicator: Spores of bacillus stearothermophilus (best indicator)
• Chemical indicator.
22.
23. Efficiency of the filtration:
retain Serratia marcescens average pore diameter 0.75 µm or less.
Types of the filters:
Asbestos (sietz filter)
cellulose acetate (membrane filter)
Candle filters
Sintered glass filters
HEPA filters
24.
25.
26. Example: gamma rays (from Cobalt 60 source).
Mechanism: breakage of DNA without temperature rise (cold sterilization).
Uses:
• Disposable plastics, e.g. rubber or plastic syringes, infusion sets and catheters.
• Catgut sutures, bone and tissue grafts and adhesive dressings, antibiotics and hormones.
Advantages of Ionizing radiation:
• ○○ High penetrating power,
• ○○ Rapidity of action
• ○○ Temperature is not raised
31. Destroys
1. All vegetative bacteria (except TB bacilli)
2. Enveloped viruses
3. Some fungi, but not bacterial spores.
Examples
1. Quaternary ammonium compound
32.
33. Destroys
• All vegetative bacteria (including tubercle bacilli)
• Enveloped and some non-enveloped viruses
• Most fungi, but not bacterial spores.
Examples
1- Alcohol
2- Phenol group
3- Halogens: - Iodine and iodophore
- chlorine, hypochlorites
34. • Examples:
1. Ethyle alcohol 70%
2. Isopropyl alcohol 35% (less volatile, more cidal)
• Uses:
1. Topical antiseptics (70%)
2. Disinfect the surface of medical equipment (Thermometer)
35. • 5% used as disinfectant of stool in typhoid or
sputum in T.B
• 1% bactericidal
-Surface and household disinfectants
-Mouth washes
-Scrub soaps
• 0.5% preservative for sera, vaccines
• remain active in presence of organic matter
• Irritant to skin, offensive odor
Phenolic derivatives
*Lysol =Crysol
*Chlorhexidine 10%+ certrimide 1% =
Savlon
*Chloroxylenol = Dettol
40. It is a chemical sterilant; often used in conjunction
with H2O2, to disinfect hemodialyzers.
It is also used for sterilizing endoscopes.
41. • Example:
2% (cidex) for 20 min
• Uses: (cold sterilant)
Very potent disinfectant
endoscope
• Disadvantages:
Highly toxic used under trained supervision in a well ventilated setting and
with appropriate PPE
Inactivated by organic matter (prior cleaning)
Active at alkaline PH
42. Ortho-phthaladehyde
(OPA)
• Example:
0.55% (cidex OPA) for 10-12 min
• Uses: high-level disinfection
endoscope
• Advantages: (over glutaraldehyde)
Not irritant to the eyes and nasal passages, does not require exposure monitoring
fast acting, has good material compatibility, and does not coagulate blood or fix tissues
to surfaces
stability in a broad range of pH (3–9) and not require activation
43. • Example:
Formalin
Formaldhyde gas
• Uses:
Disinfectant in both liquid and gaseous state
• Disadvantages:
Potential carcinogen
44. • Used for heat- and moisture- sensitive medical
devices
1- Ethylene oxide gas
2- Hydrogen peroxide gas plasma
45. Plasma is the fourth state of matter
Produced in strong
electromagnetic field
The plasma is combined with H2O2
e.g.; surgical instrument,
endoscopes
46.
47.
48. Case Scenario
2
1
3
4
• In an operation room, during an Orthopaedic surgery, one
of the surgical instruments accidentally dropped on the
theater floor. Unexperienced nurse picked it and soaked it
in cidex solution (glutaraldehyde) only for one minute then
gave it to the surgeon. The patient developed
postoperative surgical site infection.
49. 1- How long should instruments be soaked in cidex (glutaraldehyde)?
2- What are the 3 levels of disinfectants? and to which level
glutaraldehyde belongs to?
3- what are the factors that affect the efficiency of disinfectant?
50. Summary & Wrap up
Sterilization destroys all microbes including
spores while Disinfection destroys all microbes
except spore.
Physical agents kill (or remove) bacteria by one of
three processes: heat, radiation, or filtration.
Chemical agents can be classified into high, low
and intermediate level disinfectants
Spaulding classification is a Strategy for reprocessing contaminated medical
devices. The system classifies a medical device on the basis of risk of infection into
critical, semicritical, and noncritical items
54. References or
further readings
Brooks, G. F., Jawetz, E., Melnick, J. L., & Adelberg, E. A.
(2013). Jawetz, Melnick, & Adelberg's medical microbiology. New
York: McGraw Hill Medical.
Murray, Patrick R., Ken S. Rosenthal, and Michael A. Pfaller.
2018. Medical microbiology. Philadelphia: Elsevier/Saunders.
http://www.clinicalkey.com/dura/browse/bookChapter/3-s2.0-
C20100666946.
Textbook of Medical Microbiology and Immunology 2020-2021:
Textbook by staff members of medical Microbiology and Immunology
Department.
