2. Sterilization grew partly out of preservation and
also by trying to prevent infection caused by
bacteria.
Nicolas Appert-1809 heat as a preservative
method.
Louis Pasteur -1865 invented pasteurization.
Charles Chamberland –1879 invented
pressure steam sterilizer (autoclave).
Joseph lister-1880 invented carbolic acid
spray.
HISTORY
4. DEFINITIONS
Sterilization – process by which an article,
surface or medium is freed of all living
microorganisms either in the vegetative or
spore state.
Disinfection – process of destroyingall
pathogenic microorganisms capable of
producing infections but not necessarily
spores.
5. Asepsis – It refers to the complete absence of
viable pathogenic microorganisms in any
environment.
Antiseptics – Chemical disinfectants which
can be safely applied to skin or mucous
membrane and are used to prevent infection
by inhibiting growth of bacteria.
Bactericidal – Agent which can kill bacteria.
Bacteriostatic – Agent which only prevents
multiplication of bacteria.
DEFINITIONS
6. HOW CAN MICROORGANISMS
BE KILLED ??
Denaturation of proteins
Oxidation
Filtration
Interruption of DNA synthesis/repair
Interference with protein synthesis
Disruption of cell membranes
7. Most Resistant
Endospores
Mycobacteria
Fungal spores
Small non-enveloped viruses (polio,
rota virus, rabies)
Vegetative fungal cells
Enveloped viruses (Herpes,
Hepatitis B and C, HIV)
Least Resistant
8. Proposed by Earl H. Spaulding
Categorized into 3 categories
Critical devices
Semi critical devices
Non critical devices
CLASSIFICATION OF MEDICAL
DEVICES FOR REPROCESSING
17. HOT AIR OVEN
Kills by oxidation effects
Utilizes dry heat to sterilize
Used to sterilise culture
media, petri dish, specimen
bottle,culture bottle and test
tubes,liquid paraffin
21. TEMPERATURE BELOW 100o C
(PASTEURISATION)
.
❖ HOLDER METHOD – Heating
at 63o C for 30 minutes.
❖ FLASH PROCESS – Heating at
72o C for 15-20 seconds.
23. Vegetative bacteria are killed at 90-100 o C.
Requires immersion in water and boiling for
10-30 minutes.
TEMPERATURE AT 100o C
(BOILING)
24. TYNDALLISATION
❖ Steam at 100o C for 20 mins for 3 consecutive
days
PRINCIPLE - The first exposure kills all vegetative
forms and bacteria and spores which survived
the heating process will germinate into
vegetative state and are killed in subsequent
exposure.
25. TEMPERATURE ABOVE 100O C
(AUTOCLAVE)
❖ Most reliable method of sterilisation.
❖ Works on the principle of Steam under
pressure.
❖ Invented by Charles
Chamberland in 1879.
26. TYPES OF AUTOCLAVES
Gravity displacement sterilisers
High vaccum sterilisers
Autoclaves used in health care setting
laboratory autoclave
Hospital dressing sterilisers
Instrument sterilisers
40. IONISING RADIATION
Lethal action – breakdown of single stranded or
sometimes double-stranded DNA and effect on
other vital cell component
X-rays, gamma rays and beta
rays
44. MODES OF ACTION OF
CHEMICAL DISINFECTANTS
Protein coagulation
Disruption of cell membrane
Removal of free sulfhydryl groups
45. ALCOHOLS
Ethanol (80% v/v ethyl alcohol) or 2-propanol
(60-70% v/v iso- propyl alcohol) solutions are
used to disinfect skin and decontaminate clean
surfaces.
47. FORMALDEHYDE
Formalin is 37% w/v formaldehyde gas in water
Bactericidal, sporicidal, virucidal
13% v/v formalin is a good
decontaminant (but has an irritating odour)
8% v/v formalin in 80% v/v alcohol
is effective against vegetative bacteria,
spores and viruses
48. Concentration: Glutaraldehyde is commercially available
as 2% w/v aqueous solution which must be made alkaline
to "activate" (e.g. by addition of 0.3% sodium
bicarbonate).
A 2% glutaraldehyde solution, for at least 10 hours, can
be used to sterilize heat labile items.
GLUTARALDEHYDE
49. Use: for instruments such as
cystoscopes, bronchoscopes,
corrugated rubber anesthetic
tubes, face masks, endotracheal
tubes, metal instruments,
polythene tubing.
50. These are inexpensive, broad spectrum
chlorine releasing disinfectants of choice
against viruses, including hepatitis B virus.
Aqueous solution of sodium
hypochlorite (5.25%) is called
household bleach.
HYPOCHLORITE
51. PHENOLS
Effective against bacteria (especially gram +ve
bacteria) and enveloped viruses.
Used for decontamination of the hospital
environment, including laboratory surfaces.
Ex Cresol, Chlorhexidine,
Chlorxylenol, Hexachlorophines
60. GASES
ETHYLENE OXIDE
It is an alkylating agent.
Exerts lethal effect on proteins of bacteria.
It is gas at ordinary room temperature and
active against all types of bacteria and spores.
62. BETAPROPIOLACTONE
(BPL)
It is a condensation product of ketone and
formaldehyde having a boiling point of 163’C.
It is capable of killing all microorganisms including
viruses.
63. Sterilization and Disinfection are costly and
time consuming process.
However it is essential in all health care
facilities to avoid spread of disease.
It depends on the ethics of the instrument
users.
Users should keep in mind that contaminated
instrument present risk to patient as well as
the user himself.
CONCLUSION
