Getting cleaning and disinfection right: Application techniques

BY DR TIM SANDLE  |  12 DECEMBER 2022

 

 

Sections 4.33 to 4.36 of the 2022 edition of EU GMP Annex 1 focus on cleaning and disinfection. In this GMP blog, we look at cleaning and disinfection techniques.


For effective cleaning, the application technique is important. Wiping strategy includes the applied pressure force, wiped surface area, the geometry of the mechanical action, the number of passages.

Each of these is influenced by the presentation.

 

 

There are five primary means of application:

 

Spray, with no wiping

  • This method is the least effective. the absence of mechanical action means there is no physical activity to disassociate organisms from the surface and no direct application and hence penetration of the cleaning agent towards the soil. This method is best avoided.


Spray and wipe

  • Although there is a wiping aspect, the application of the cleaning agent can be difficult to apply leading to either overspray or with some parts of the surface being missed. The use of pre-saturated wipes (see below) can be more effective

Dip and wipe

  • The sipping of a wipe into a disinfectant solution is hard to control, especially given the short contact time that the wipe is in contact with the solution for which limits the concentration applied to the wipe and the even distribution of the agent across the wipe

  • With wipes, the surface of the wipe should not be used more than once (as part of the ‘one wipe side, one application, one direction’ strategy). An economy can be introduced by folding the wipe so that four surfaces are available (the four-fold wipe technique). It is important to avoid inappropriate reuse of the towelette as this may promote the accumulation of microorganisms and raise the risk of cross-contamination during the cleaning or disinfection process. With mops, the rinsing of the mop and reapplication enable the mop to be reused for the duration of a cleaning session

Soak and wipe

  • This method is the “bucket method”, where a wipe or mop is soaked into a detergent or disinfectant solution for a recommended time period. The material is then wrung out to remove the excess solution and directly applied to a hard surface. This method allows a relatively long contact time ensuring enough active ingredient load in the towelette before use

  • It is important to understand any possible interactions between wipes and detergent or disinfectant based on a longer soaking time or with any chemical binding of the active ingredient to the wipe which could lead to a decrease in concentration in the bulk solution

  • With the techniques for the cleaning and disinfection of cleanroom floors, either the “two-bucket” or the “three-bucket” technique is recommended. Both of these techniques involve using a bucket of disinfectant and a bucket of water. In the “two-bucket” technique there is a “wringer” (for the mop) over the bucket of water. In the “three-bucket” technique there is a third bucket, empty except for having a wringer mounted over it. To illustrate this, the three-bucket technique involves:

    - Dipping the mop in disinfectant
    - Mopping the floor
    - Dipping the mop in the bucket of water
    - Rinsing the excess water off the mop head into the third (empty) bucket
    - Dipping the mop in disinfectant
    - Repeating

  • Surface wiping or mopping should be carried out from top to bottom, from back to front and from cleanest to dirtiest, changing the wipe at appropriate intervals

 

Pre-saturated wipes or mop heads

  • Pre-saturated wipes or mop heads come with the active ingredient pre-soaked into the material. It is important to assess whether the supporting efficacy studies from the manufacturer have been based on the material and cleaning solution in tandem and not simply upon the detergent or disinfectant as a separate study. An understand is also required of the amount of liquid released and for how long the pre-saturated material can be used for. Care must be taken when opening packets of pre-saturated wipes since remaining wipes will begin to dry out and lose a quantity of the impregnated liquid once the packet is opened, leading to an eventual loss of efficacy at a given time point. 



Based on the above, the cleaning technique used for cleanrooms should be defined and standardised. It does not matter how effective the cleaning agents selected are if the cleaning technique practised by cleanroom operators is poor.

 

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