Methods of Processing Instrument

Methods of Processing Instrument


The use of physical or chemical means to remove, inactivate, or destroy pathogens on a surface of item to the point where they are no longer capable of transmitting infectious particles and the surface or item is rendered safe for handling, for use, or for disposal. Decontamination is the first step in handling used instruments. Immediately after use, all instruments should be placed in an approved disinfectant such as 0.5% chlorine solution for 10 minutes to inactivate most organisms, including HBV and HIV. Decontamination could comprise cleaning, disinfection or sterilization as appropriate.

Table 5.1 Effective Methods of Processing Instrument

Method Effectiveness (Kill or Remove Microorganisms) End Point
Decontamination Kills HBV and HIV and most microorganisms 10 minute soak
Cleaning (water only) Up to 50% Until visibly clean
Cleaning (soap and rinsing with water Up to 80% Until visibly clean
High level disinfectant 95% (does not inactivate some endospores) Boiling, steaming or chemical for 20 minutes
Sterilization 100% High-pressure steam, dry heat or chemical for recommended time


Any process, chemical or physical, that destroys pathogens such that an item is safe to handle for its intended use. The process does not necessarily kill or remove all micro-organisms, but reduces their number to a level which is not harmful to health.


A disinfectant is a chemical agent that destroys most pathogens but may not kill bacterial spores. Chemical disinfection should only be used if heat treatment is impractical or if heat may cause damage to the equipment. There is a broad spectrum of chemical disinfectants that have different anti-microbial activities. Most of them do not necessarily kill all microorganisms or spores that are present on an inanimate object but instead reduce the number of microorganisms to a level that is not harmful to health. Disinfectants are used on inanimate objects only and not on living tissue. Chemicals used to kill microorganisms on skin or living tissue are known as antiseptics. The broad category of disinfection may be subdivided into high-level, intermediate-level, and low-level disinfection according to the anti-microbial activity of the disinfectant.

  • Low level disinfectant (LLD): LLD is an agent that destroys all vegetative bacteria (except tubercle bacilli), lipid viruses, some nonlipid viruses, and some fungus, but not bacterial spores.
  • Intermediate-level disinfectant (ILD): ILD is an agent that destroys all vegetative bacteria, including tubercle bacilli, lipid enveloped (HIV, herpes, hepatitis B and C virus)and some nonlipid enveloped (coxackie, enteroviruses, etc) viruses, and fungus spores, but not bacterial spores.
  • High-level disinfectant (HLD): A high-level disinfectant is a chemical or physical agent or process that is capable of killing some bacterial spores when used in sufficient concentration, temperature, and under suitable conditions. It is therefore expected to be effective against vegetative bacteria, fungi, viruses and other microorganisms. It does not kill high numbers of bacterial spores.

Commonly used disinfectant

A number of disinfectants are commercially available in most countries including Ethiopia, four disinfectants-chlorine, glutaraldehyde, formaldehyde and hydrogen peroxide are routinely used for HLD. Alcohols and iodophors are disinfectants and not high- level disinfectants and should not be used for HLD purpose.

A 0.5% chlorine solution (Barkina) can be made from readily available liquid or powder chlorine. Liquid chlorine is available under different brand names in different concentration for example "Ghion" available in Ethiopia contains 5% chlorine. Manufacturers of, widely used brand Sedex, contains 5% chlorine.

Achieving satisfactory decontamination is dependent on:

  • Make fresh solution every morning, or more often if the solution becomes cloudy.
  • Use plastic, non-corrosive container for decontamination. This prevents sharp instruments from getting dull due to contact with metal containers. It also prevents instruments from getting rusted due to chemical reaction (electrolysis) that can occur between two different metals when placed in water.
  • Do not soak metal instruments in water for more than one hour, even if they are electroplated, to prevent rusting.
  • Do not mix chlorine solutions with either formaldehyde or with ammonia-based solutions as toxic gas may be produced.
  • Place all instruments in 0.5% chlorine solution for 10 minutes immediately after completing the procedure.
High-Level Disinfection by Boiling

Although boiling instruments in water for 20 minutes will kill all vegetative forms of bacteria, viruses, yeast and fungi, boiling will not kill all endospores reliably

Last modified: Wednesday, 16 November 2016, 7:24 AM