Sterlisation and disinfection: A review

Introduction

The main purpose of sterlisation as well as disinfection is inhibiting the growth as well as transmission of the microorganisms or pathogens that are capable of doing infection. Inhibition of growth or transmission of microorganisms should be done in two ways, first is the prevention of the vertical transmission and second is the prevention of the lateral transmission.1, 2, 3, 4 Vertical transmission is the one in which there is propagation of microorganisms from one generation to the other generation and lateral transmission is the one in which there is transfer of resistance of pathogen to the other pathogen of the same generation and along with it there will be spreading of the pathogen to the surrounding.

To prevent the spread the of vertical transmission, there should be proper use of antibiotics. And to prevent the lateral transmission is by the help of health care workers by hygiene maintenance, by the process of hand hygiene measure, maintaining hygiene by the process of disinfection in the surrounding area, health care workers must be having adequate knowledge disinfection measures.5, 6, 7, 8

Both the processes i.e. disinfection as well as sterlisation both occurs at the molecular level. Both the processes i.e. sterilisation and disinfection requires electrons for the process of oxidation, acidification and coagulation

Sterilisation

It can be defined as the process by which an article or surface or medium is made free from all the microorganisms either in the vegetative or in the spore form.

Disinfection

It is the process which helps in destruction of all pathogens that are capable of producing infection but not the spores necessarily. In the process of disinfection all the organisms that are capable of producing infection might not be killed by the process of disinfection but the number of infection causing microorganisms got reduced to the level that is not at all harmful to health.9, 10, 11, 12, 13, 14, 15, 16

Moist Heat Sterlisation

The most common example of using moist heat sterlisation is the use of autoclave. Autoclave is most commonly used in dental practice for the proper sterlisation of the dental instruments. Autoclave works on the principle of saturated steam. Most of the bacteria are more susceptible to moist heat sterlisation as bacterial proteins coagulates more readily by moist heat sterlisation as literature stated that moist heat can penetrate the material easily especially the porous material. It works on the principle of saturated steam which stated that whwn staeam comes in direct contact with the surrounding cooler surface it condenses in to water and results in liberation of latent heat to that surface. So the condensed water results in production of moist conditions that are responsible for the destruction of the microorganisms present over the surface of the article. Temperature sets at 121 degree Celsius for 15 minutes with the pressure of the chamber at 15 pounds, some other holding temperature for autoclave is at 126 degree Celsius for 10 minutes at 20 pound per square inch or at 133 degree Celsius for 3 minutes at 30 pounds per square inch. This equipment is used to sterlise the gowns, dressings, gloves, useful for all the materials that cannot with stand higher temperature of the hot air oven. One should take proper care of arranging the article to be autoclaved in such a manner, such that to ensure the free circulation of the steam inside the chamber. Spores of geobacillus stearothermophilus are use to check the proper sterlisation, brownes tube can also be used, brownes tube contains red solution when ultimately after proper sterlisation turns in to green.18, 19

Radiations

Gamma rays, x rays and cosmic rays come under the category of ionizing radiations. They have a high penetrating power. They can damage DNA by various mechanisms. These gamma rays are most commonly used for the process of sterlisation of plastic syringes, cannulas, culture plates. The other type of radiations that include infrared radiations and ultraviolet radiations comes under the category of non ionizing radiations. These radiations are most commonly used to disinfect laboratory areas, operation theatres.

Alcohols

Ethyl alcohol and isopropyl alcohol are most commonly used alcohol in dentistry. They are used most commonly as topical antiseptic agents. They act by the process of denaturating of bacterial protein.

Aldehydes

Formaldehyde falls under this category. It is basically bactericidal, sporicidal as well as virucidal. It is used in the concentration of 10 percent aqueous. It is most commonly used as tissue preservation for the process of histological examination. It is also helpful in sterlising bacterial vaccines. The second most commonly used aldehyde is glutaraldehyde. It very much effective against bacteria, viruses and fungi. it is used in the concentration of 2 percent as buffered solution. Glutaraldehyde is most commonly used in the sterlisation of endoscopes, bronchoscopes.

Phenols

The derivatives of phenols such as cresols, chlorhexdinie and hexachlorophene are most commonly used in dentistry and they used as antiseptics. Cresols most commonly used in the cleaning of the floor, disinfection of the excreta. Chlorhexidine solution is the most commonly used solution as an antiseptic mouth wash in the field of dentistry. They are mostly active against gram positive bacterias as compared to the gram negative bacteria.

Halogens

Chlorine and iodine falls under the category of the halogens. Chlorine is most commonly used in water supply, in swimming pools. Chlorine most commonly used in the form of bleaching powder, sodium hypochlorite solution. Its mechanism of action is basically due to release of free chlorine ions.

Oxidizing Agents

Most commonly used oxidizing agent is hydrogen peroxide in the concentration of 5 to 6 percent and is effective against most of the organisms at this concentration, hydrogen peroxide is effective over spores also at higher concentration of 10 to 25 percent. Its mechanism of action is basically from liberation of free hydroxyl radical. It is most commonly used in the disinfection of lenses, surgical prosthesis.

Salts such as copper, silver or mercury can be used as a disinfectant, as they have toxic effect on bacterial cell wall. Gases like formaldehyde gas, ethylene oxide are most commonly used as fumigation of operation theatres, ethylene oxide gas is mostly effective on most of the bacteria and viruses including spore form also, used for sterlisation of disposable needles.16

Conclusion

It is very much required to have an adequate knowledge of various materials that can be used for disinfection as well as sterlisation. As now a days sterlisation is very much helpful in inhibiting the spread of infection from dentist to the patient as well as from patient to the dentist.

Source of Funding

None.

Conflict of Interest

The authors declare no conflict of interest.