PHYSICAL AND CHEMICAL METHODS OF STERILIZATION Flashcards by siomai a

◦ Killing all microbial forms and spores.

Sterilization

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◦ Killing of microorganism without necessarily destroying the endospores

Disinfection

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◦ Chemical agents to prevent spread of bacteria

Antisepsis

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◦ Agent that kills bacteria

Bactericidal / Germicidal

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◦ Inhibiting the growth of bacteria without killing them

Bacteriostatic agent

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Agents that destroys spores, fungi, & viruses.

Sporicidal / Fungicidal / Viricidal

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Physcial methods of sterilisation

Heat, radiation, filtration

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Why we need sterilization?

Microorganisms capable of causing infection are constantly present in the external environment and on the human body.
Microorganisms are responsible for contamination and infection
The aim of sterilisation is to remove or destroy them from materials or from surfaces

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How can microorganisms be killed?

Denaturation of proteins, oxidation, filtration, interruption of DNA synthesis/repair, Interference with protein synthesis, Disruption of cell membrane

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Two types of sterilization:

physical and chemical

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Physical sterilization includes:

heat(dry heat or moist heat), radiation, filtration, sunlight

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Chemical sterilization includes:

alcohols, aldehydes, phenolics, oxidizing agents, quartenary ammonium compound, ethylene oxide gas, others

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Uses of sterilization

Sterilization of materials, instruments used in surgical and diagnostic procedures.

sterilization of media and reagents used in the microbiology laboratory

food and drug manufacturing to ensure safety from contaminating organisms.

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suffix cide

to kill

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viricide, fungicide, bactericide

destroy virus, destroy fungi, destroy bacteria

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suffix static/statix

meaning to stand still. indicating that the agent will prevent the growth or multiplication of the type of organism but are not killed outright.

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HIGHEST RESISTANCE

Bacterial endospore

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Moderate resistance

Protozoan cyst, some fungal spores, some naked virus, vegetative bacteria that have higher resistance (m. tuberculosis, s.aeuris, Pseudomonas)

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Lease resistance

most bacterial vegetative cells or ordinary fungal spores and hypae enveloped virus, yeasts, trophozoites

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What to sterilize?

all instruments that penetrate soft tissues and bone

instruments that are not intended to penetrate the tissues, but that may come into contact with oral tissues

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If the sterilization procedure may damge the instruments, then, sterilization can be replaced by ____ procedure

disinfection

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Ideal sterilization/ disinfection process

highly efficacious, fast, good penetrability, compatible with all materials, non toxic, effective despite presence of organic material, difficult to make significant mistakes in process, easily monitored

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Active germicidal effect due to its content of ultraviolet rays
natural method of sterilization of water in tanks, rivers, and lakes.

Sun light

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Most common method of physical sterilization

heat

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◦ The minimum time required to kill a suspension of an organism at a predetermined temperature and environment. ◦ originally developed for food canning and has found applications in cosmetics & pharmaceuticals.

Thermal Death Time

FACTORS AFFECTING THE STERILIZATION PROCESS THROUGH HEATING

Nature of the heat, Temperature and Time, Number of Microorganism, Type of Material, Presence of Organic Material

Moist heat has greater killing action than dry heat

Nature of the heat

Inversely proportional

Temperature and Time

◦ Directly proportional with temp and time

Number of Microorganism

◦ Heat sensitive; heat resistant

Type of Material

◦ Fats, proteins & sugars need higher temperature.

Presence of Organic Material

 Preferred over dry heat due to its fast killing action.  Causes coagulation and denaturation of proteins

MOIST HEAT

◦ Pasteurization ◦ Vaccine Bath ◦ Serum bath ◦ Inspissation

Temperature below 100C

◦ Boiling ◦ Fractional Sterilization (Tyndallization)

Temperature at 100C

◦ Autoclave (Steam under Pressure) ◦ use of pressurized steam and high temperature to kill microbes, spores, or viruses that are hard to destroy using conventional disinfection methods.

 Temperature Above 100C

➢ Destroying disease causing organism in milk and beverages.

PASTEURIZATION

Milk is heated at 60C-65C followed by rapid cooling

CONVENTIONAL METHOD

heating at 72C for 15s followed by quick cooling to 13C.

Flash Method

(UHT): heating at 140C for 15sec and 149C for 0.5 sec

Ultra-high Temperature

serum or body fluid is sterilized in a water bath at 56C for 1 hour - vaccines are sterilized in a special water bath at 60C for 1 hour

Vaccine bath

➢ Killing of bacteria contaminating serum preparations ➢ Heating at 56C for several successive days ➢ Only the vegetative forms are destroyed

Serum Bath

This is technique to solid as well as disinfect egg and serum containing media -heated at 80-85c for 30 mnts on three successive days

INSIPISSATIONS

T or F Boiling for 10-30 minutes may kill most of vegetative forms but spores with stand boiling

Steam at 100C for 20 minutes on three successive days | - used for egg, serum, and sugar containing media

Tyndallization

- steam at 100C for 90 minutes | - used for media which are decomposed at high temperature

Steam sterilizer

➢ process for sterilizing food substances ➢ named after its inventor, scientist John Tyndall ➢ can be used to kill heatresistant endospores. ➢ Exposed to live steam at 100C for 30-90min for 3 consecutive days. ➢ Fractional sterilization ➢ Selenite broth ➢ TCBS(Thiosulfate Citrate Bile Salt-Sucrose Agar)

Tyndallization

Temperature Above 100C ◦ Autoclave (Steam under Pressure) ◦ use of pressurized steam and high temperature to kill microbes, spores, or viruses that are hard to destroy using conventional disinfection methods

moist heat

What are sterilization conditions:

sterilization conditions: temperature- 121C , chamber pressure -15lb per square inch, holding time-15 minutes,

Uses of autoclaves

For materials which can not withstand high temp. to sterilize culture media, rubber material, gowns, dressings, gloves, etc

(killing or removal of all microorganisms, including bacterial spores) technique  requires longer exposure time (1.5 to 3 hours) and higher temperatures

DRY HEAT

Various methods of dry heat sterilization are; ___,___.___

Various methods of dry heat sterilization are; hot air oven, incineration, flaming (wire loop) etc

◦ Wire loops, straight wires, forceps & spatulas ◦ Until they become red hot

RED FLAME

 high temperature, short time processin  applied to sealed metal cans.  applicable to processing of both high and low acid products  used to exhaust packs to produce a high vacuum when cooled. Passing the article over a bunsen flame, but not heating it to redness

FLAMING

Use of flaming

Scalpels, mouth of test tubes, flasks, glass slides, cover slips

a waste treatment process that involves the combustion of organic substances contained in waste materials. "thermal treatment" converts the waste into ash, flue gas and heat.

Incineration

 Depriving the microorganism of moist  For food preservation like preparation of dried fish & fruits  Destroys vegetative form  Endospores are not killed

dessication

 method of preserving food by lowering the temperature to inhibit microorganism growth. by immersion in an ice and salt brine.

Freezing

Lyophilization

(freeze-drying

Does not destroy but removes the microorganisms. It is used for both the clarification and sterilization of liquids and gases as it is capable of preventing passage of both viable and non viable particles used for the removal of microbes from solutions that cannot easily be treated in other fashions. Typically head-sensitive compounds such as antibiotic and vitamis

Filtration

Major mechanisms of filtration:

sieving, adsorption, and trapping within the matrix of the filter material ex HEPA FILTERS

Several types of filters

candle filters, asbestos disc filters, sintered glass filters, membrane filters, air filters, syringe filters

Examples of this are electromagnetic radiation, particulate radiation. The major target of this is microbial DNA. Useful method for the industrial sterilization of heat sensitive products. Articles in dry state like surgical instruments

Radiation Sterilization

Non ionizing radiation:___ &___ | ionizing radiation:___ &___

Non ionizing radiation: Infrared radiation and UV radiation | Ionizing radiation: X-rays & Gamma Rays

 Exposure to sound waves frequency  20,000 cycles/sec for one hour can kill some bacteria and viruses  To disinfect instruments and reduce microbial load

Sonic and ultrasonic vibrations

- High concentrations of salt or sugar in foods to inhibit growth - cells in hypertonic solution of salt or sugar lose water - fungi have greater ability than bacteria to survive hypertonic environments

Osmotic Pressure

Effective Chemical Disinfectant

Broad spectrum of activity Fast acting Inexpensive Easy to apply Odorloss Non toxic to human tissues

for skin, clinical thermometers, cabinets, incubators | Ethanol (80% v/v ethyl alcohol or 2-propanol (60-70% v/v isopropyl alcohol)

Alcohols

To preserve anatomical specimen, sterilizing incubators and heat sensitive catheters, clothing bedding furniture; fumigation

Aldehydes

Affective against tubercle bacilli, fungi, and viruses. Also for plastics, rubbers, and metals

Gluteraldehyde

Aniline and acridine dyes for skin and wound antisepsis. Affective against Gm+ ve.

Dyes

Aqueous solutions of iodine, Chlorine

Halogens

Microbicidal

Phenols

In aqueous solution it acts as a bactericidal and sporicidal. active against gram -ve bacteria, spores, viruses (hiv) and fungi

formaldehyde (formalin)

Effective agains bacteria and eveloped viruses.

Phenol

The seventh column of the periodic table of elements

Halogens

Two halogens are regularly employed as antimicrobials

iodine and chloride

Commonly used as an antiseptic against all microbes, fungi, and viruses. It inhibits protein synthesis and oxidizes -SH groups of amino acids

Iodine

Used as disinfectant Hypochlorous acid is a product, formed in water, that is the active from of the disinfectant applied in treatment of drinking water, swimming pool and sewage

Chlorine

What are the heavy metals?

mercury, silver, zinc, arsenic, copper ions

form precipitates with cell proteins. At one time were frequently used in medically as antiseptics but much of their use has been replace by less toxic alternatives

Heavy Metals

 group of chemical compounds that lower the surface tension of water.

Surface Active Agents

are the major ingredients in soaps and detergents.

Surfactants

Kind of dyes

Aniline dyes and acridine dyes

Skind and wound antiseptics, bacteriostatic in high concentrations

Dyes

used as a disinfectant and sterilant both in the liquid and gaseous states. Is sold and used principally as a water based solution called formalin. The acqueous solution is bactericidal, tuberculocidal, fungicidal, virucidal, and sporicidal

Formaldehyde

is the process of sterilizing the producrs that are used in medical and pharmaceuticals.

ETO (Ethylene Oxide)

ETO gas sterilization process is carried out in four different constituents:

concentration of gas, humidity, temperature, and time.