This presentation contains needed information for a medico on different physical methods of sterilization and disinfection. I haven't prepared slides for chemical methods. If anyone wants, he or she can put it in the comments section below. Also, some pictures have not been labeled but are mostly in the sequence (some pictures could be missing). If anyone wants to know any particular picture, he or she can put it in the comments section below.

1. STERILIZATION AND
DISINFECTION

2. INTRODUCTION
 STERILIZATION : Destroys or removes all living organisms
including viable spores
• reduction of at least 106 log colony-forming units of
microorganisms and their spores
• achieved by a physical agent or a chemical agent

3.  DISINFECTION : Destroys or removes all/ most pathogenic
organisms but not bacterial spores
• reduction of at least 103 log colony-forming units of
microorganism, but not spores
• By physical and chemical agents, but used only on inanimate
objects
 ASEPSIS : Chemical agents (called antiseptics) applied on
body surface to kill or inhibit microorganisms
• prevent the entry of pathogens into sterile tissues and thus
prevents infection or sepsis
• generally not as toxic as disinfectants as diey must not
destroy too much of host tissue

4.  DECONTAMINATION (OR SANITIZATION) : Reduction of
pathogenic microbial population to a level at which items
are considered as safe to handle without protective attire
• reduction of atleast 1 log colony-forming unit of most of the
microorganisms, but not spores
• manual or mechanical cleaning by soap and detergents to
eliminate debris or organic mater from the medical devices
 ‘cides’ – to kill microorganisms eg: bactericide, virucide,
fungicide
 ‘statics’ – inhibit microbial growth eg: bacteriostatic,
fungistatic

5. FACTORS INFLUENCING EFFICACY OF
STERILANT/ DISINFECTANT
1. Organism load – Larger microbial populations > smaller
microbial populations
2. Nature of Organisms - Prions (highest resistance) >
Cryptosporidium oocysts > Bacterial spores > Mycobacteria
> Other parasite cysts (e.g. Giardia) > Small non-enveloped
viruses> Trophozoites > Gram-negative bacteria> Fungi >
Large non-enveloped viruses> Gram-positive bacteria >
Enveloped viruses

6. 3. Concentration of the chemical sterilization or temperature
of heat sterilization
4. Nature of sterilant/ disinfectant
5. Duration of exposure
6. Temperature
7. Local environment
• pH – heat kills more readily at an acidic Ph
• Organic matter – can provide protection for microbes
• Biofilm -

8. PHYSICAL AGENTS
1. DRYING : does not affect many microbes and spores
2. HEAT : most common and reliable
 DRY HEAT - kills by charring, denaturation of bacterial protein, oxidative
damage and by the toxic effect of elevated levels of electrolytes
• Flaming - Long time (eg: inoculating loops or wires), short time (eg: mouth
of test tubes
• Incineration – 870-1200 degrees
• Hot air oven – electrically heated, at 160 degrees for 2 hrs (eg: glassware,
surgical instruments) , lots of precautions, spores destroyed
 MOIST HEAT - kills by denaturation and coagulation of proteins
• Temp < 100 degrees – Pasteurization (non sporing), Water bath (serum,
body fluids and vaccines), inspissation (fractional sterilization for serum
based media)
• Temp = 100 degrees – boiling, steaming, tyndallization
• Temp > 100 degrees - Autoclave

13. AUTOCLAVE
 Principal : similar to pressure cooker
 Components : pressure chamber (with steam jacket), lid, electric
heater
 Biological indicator : Geobacillus stearothermophilus
 Uses : method of choice for -
• Surgical instruments
• Culture media
• Autoclavable plastic cotainers
• Plastic tubes and pipette tips
• Solutions and water
• Biohazardous waste
• Glassware (autoclave resistible)

15. 3. Filtration:
• Depth filters (candle filters, asbestos filters etc)
• Membrane filters – most widely used for bacteria
4. Radiation
• Ionizing (highly penetrable, does not heat) – X-rays, gamma
rays, cosmic rays
• Non ionizing – UV rays and Infrared