This ppt explains about sterilisation and disinfection . Dr. C P Prince is an eminent microbiology teacher with years of teaching practice.

1. STERILIZATION
AND
DISINFECTION
Dr. C P Prince
HOD & Associate Professor
Department of Microbiology,
Mother Theresa Post Graduate & Research Institute of Health Sciences
(Government of Puducherry Institution)

2. TERMINOLOGY IN STERILIZATION
• Sterilization – a process that destroys all viable
microbes, including viruses and endospores;
microbicidal
• Disinfection – a process to destroy vegetative
pathogens, not endospores; inanimate objects
• Antiseptic – disinfectants applied directly to
exposed body surfaces
• Sanitization – any cleansing technique that
mechanically removes microbes

3. TERMINOLOGY IN STERILIZATION
• Degermation – mechanically removing microbes
form surface (skin) such as surgical hand
scrubbing, or wiping skin with alcohol prior to
venipuncture
• Sepsis – bacterial contamination
• Asepsis – absence of significant contamination
• Bactericidal (microbicidal) - -cidal means kill
• Bacteriostatic (micro biostatic) - -static means
inhibition of growth and multiplication

5. AIM OF STERILIZATION - ASEPSIS
• Asepsis is the practice to reduce or eliminate
contaminants (such as bacteria, viruses,
fungi, and parasites) from entering the
operative field in surgery or medicine to
prevent infection. Ideally, a field is "sterile"
— free of contaminants — a situation that is
difficult to attain. However, the goal is
elimination of infection, not sterility.

6. HOW STERILIZATION WORKS
• Cell wall maintains integrity of cell . When
disrupted, cannot prevent cell from bursting due
to osmotic effects
• Cytoplasmic membrane contains cytoplasm and
controls passage of chemicals into and out of cell,
When damaged, cellular contents leak out
• Viral envelope responsible for attachment of virus
to target cell .Damage to envelope interrupts viral
replication
• So…non enveloped viruses have greater tolerance
of harsh conditions

14. Physical Methods of Microbial Control
• Heat: Kills microorganisms by denaturing their enzymes
and other proteins. Heat resistance varies widely among
microbes.
• Thermal Death Point (TDP): Lowest temperature at which
all of the microbes in a liquid suspension will be killed in
ten minutes.
• Thermal Death Time (TDT): Minimal length of time in
which all bacteria will be killed at a given temperature.
• Decimal Reduction Time (DRT): Time in minutes at which
90% of bacteria at a given temperature will be killed. Used
in canning industry.

16. BOILING
• Kills vegetative cells of bacteria and fungi, protozoan
trophozoites, and most viruses within 10 minutes at
sea level
• Temperature cannot exceed 100ºC at sea level; steam
carries some heat away
• Boiling time is critical
• Water boils at lower temperatures at higher elevations;
requires longer boiling time
• Endospores, protozoan cysts, and some viruses can
survive boiling

17. MOIST HEAT
• Used to disinfect, sanitize, and sterilize
• Kills by denaturing proteins and destroying cytoplasmic
membranes
• More effective than dry heat; water better conductor
of heat than air
• Methods of microbial control using moist heat
• •Boiling
• •Autoclaving
• •Pasteurization
• •Ultrahigh-Temperature Sterilization

18. MOIST HEAT
• Pasteurization
• Definition: a process in which fluids are heated at
temperatures below boiling point to kill
pathogenic microorganisms in the vegetative
state without altering the fluid’s palatability.
• Conditions: 62℃, 30min or 71.7℃, 15sec
• Significance: kills vegetative pathogens
• Applications: milk, beer

19. Pasteurisation
• First used with milk: 72°C for 20 seconds
• Heating to 80°C for 1 minute will kill most
vegetative organisms
• Examples: bed-pan washer, proctoscope

20. AUTOCLAVING
• Pressure applied to boiling water prevents
steam from escaping
• Boiling temperature increases as pressure
increases
• Autoclave conditions – 121ºC, 15 psi, 15
minutes

29. PHENOL AND PHENOLICS
• Intermediate- to low-level disinfectants
• Denature proteins and disrupt cell membranes
• Effective in presence of organic matter and
remain active for prolonged time
• Commonly used in health care settings, labs, and
homes (Lysol, triclosan)
• Have disagreeable odor and possible side effects

34. SURFACTANTS
• Surface active” chemicals that reduce surface tension of
solvents to make them more effective at dissolving solutes
• Soaps and detergents
• Soaps have hydrophilic and hydrophobic ends; good
degerming agents but not antimicrobial
• Detergents are positively charged organic surfactants
• Quats – colorless, tasteless, harmless to humans, and
antimicrobial; ideal for many medical and industrial
application
• •Low-level disinfectants

35. HEAVY METALS
• Ions are antimicrobial because they alter the 3-D shape
of proteins, inhibiting or eliminating their function
• Low-level bacteriostatic and fungistatic agents
• 1% silver nitrate to prevent blindness caused by N.
gonorrhoeae
• Thimerosal (mercury-containing compound) used to
preserve vaccines
• Copper controls algal growth in reservoirs, fish tanks,
swimming pools, and water storage tanks; interferes
with chlorophyll

36. ALDEHYDES
• Denature proteins and inactivate nucleic acids
• •Glutaraldehyde both disinfects (short
exposure) and sterilizes (long exposure)
• •Formalin used in embalming and disinfection
of rooms and instruments

37. GASEOUS AGENTS
• Ethylene oxide, propylene oxide, and beta-
propiolactone used in closed chambers to
sterilize items
• Denature proteins and DNA by cross-linking
functional groups
• Used in hospitals and dental offices
• Can be hazardous to people, often highly
explosive, extremely poisonous, and are
potentially carcinogenic

38. PROBLEMS WITH STERILITY
• Lack of understanding of risk/process
• physicians introducing new products (borrowed,
samples)
• Multidose vials
• What is sterile vs not
• Lack of understanding of components of process
• less training

40. PLASMA STERILIZATION
• A plasma is a quasi-neutral collection of electrons,
positive ions, and neutrals capable of collective
behaviour
• Positive ions = free radicals
• Plasma sterilization operates synergistically via three
mechanisms:
• Free radicals interactions
• UV/VUV radioactive effects
• Volatilization
• Dead microorganisms = sterilization

41. DISADVANTAGES OF PLASMA STERILIZATION
• Weak penetrating power of the plasma species.
Complications arise in:
• Presence of organic residue
• Packaging material
• Complex geometries
• Bulk sterilization of many devices
• Solutions: Introduce preferentially targeting
UV/VUV radiation of proper wavelength

45. THANK YOU