Good Laboratory Practices and Disinfection/Sterilisation
Author: Sweta Kumari
Good Laboratory Practices
In order to avoid harm to human, animals and nature by human error or poor laboratory technique or misuse of laboratory equipment these are some standard good practices that we can keep in mind while handling infectious biological agents:
Use of pipettes and pipetting aids
Pipetting by mouth is not good practice it must be prohibited. A discard container should be kept inside the biological safety cabinet not outside, so the risk of infection could be minimised. If the pipette is contaminated then, it should be kept in a suitable disinfectant for certain periods of time.
Infectious material should not be mixed.
Reducing the dispersal of infectious materials
There should be precautions to ensure that there is no aerosol creation therefore care should be taken when drying sputum samples. The workspace must be decontaminated with suitable disinfectant at the end of each work done.
Use of biological safety cabinet
Before using the cabinets, it is better to check that it is working properly. Paperwork should not be placed inside the biological safety cabinet. There should be a minimum crowd behind the operator. The fan in the cabinet should be open at least for five minutes before and after use.
Avoiding the infectious material to enter through the route of ingestion and direct contact
Large particles during the microbiological manipulation settle on the surface of the bench and also on the hand of the operator therefore disposal gloves should be worn. The worker should not touch their eye, nose and face. Food and drink should not store in a laboratory.
Care and use of the refrigerator and freezer, etc.
All the containers should be kept with proper labelling includes the scientific name of content, the date on which the container is stored and there should be the name of the individual too who stored it. If there is an unlabelled container that should be discarded after autoclave.
Use of centrifuges
Tubes or specimen containers should be securely capped for centrifugation. Buckets must be loaded in paired weight in order to balance correctly. Distilled water or alcohol (ethanol 70%) should be used to balance the empty buckets, after use bucket should be stored in an inverted position to drain off the balancing fluid used.
Avoiding injection of infection agents
If possible then glass wear should be replaced with plastic wear because there may be inoculation from the broken or chipped glass.Disinfection/Sterilisation
Disinfection: A process by which chemical or mixture of the chemical that kills the microorganisms not necessarily spores. This can be applied to an inanimate surface or object.
Sterilisation: A process by which all class or microorganisms and spores kills or removed.
Cleaning of laboratory materials
Cleaning refers to the removal of dirt, soil and organic matter that can shield microorganisms and may interfere when we apply decontaminants (disinfectants chemical germicides) for the killing of m Therefore precleaning is essential to achieve proper sterilisation and disinfection.
Commonly used class of germicides is listed below:
Chlorine (sodium hypochlorite - NaOCl)
Hydrogen peroxide and peracids
Chlorine dioxide (ClO2)
Iodine and iodophors
Quaternary ammonium compounds
Hydrogen peroxide and peracids
Hand washing/hand - decontamination
While handling biohazardous material wear gloves and wash hands before leaving the laboratory after work. Use of germicidal based soap is recommended but usually, ordinary soap and water are also sufficient to decontaminate. If proper hand washing is not available use alcohol-based hand rubs.
Heat disinfection and sterilisation
A physical agent heat is most commonly used for decontamination of pathogenic organisms. Dry heat is used to process laboratory wear it is totally not corrosive at the temperature of 160 degrees Celsius or higher for two to four hours.
The quality of steam used is saturated steam under pressure. These are some following cycles:
1. 3 min holding time at 134 °C
2. 10 min holding time at 126 °C
3. 15 min holding time at 121 °C
4. 25 min holding time at 115 °C.
The operation should be assigned to the trained individual. There should be a regular inspection by qualified personnel to check the chamber, door seals and all gauges and controls. The operator must wear suitable gloves while opening the autoclave. If the drain screen filter of the chamber is available then it should be cleaned up daily. There are chances that the relief valves of the pressure cooker autoclave may block due to paper etc in load therefore care should be taken to ensure that this does not happen.
Laboratory biosafety manual. (2004). weblink