Keeping the cleanroom clean requires that several factors be taken into consideration
when designing a cleaning and disinfection regime, such as user requirements and types
of disinfectants available. The principle aims of an effective cleaning and disinfection
regime are microbiological and particulate control appropriate to the grade of area, and
also using correct, safe and well documented materials as not to damage the surfaces or
Basic cleaning is the process of removing residues and soiling from surfaces to the extent
that they are visually clean. This will slightly reduce the microbial population, but will not
achieve the same level of kill as a disinfectant. It is important that surfaces to be disinfected
must be clean as disinfectants can be chemically inactivated by the presence of soiling and
in turn create a physical barrier preventing the disinfectants reaching the microbial cells.
When selecting a cleaning agent it is significant to choose a known composition that is
compatible with the surface to be cleaned along with the disinfectants in use. Lowfoaming
or non-foaming agents are preferred, since they are easy to rinse which avoids
residue formation. If the cleaning agent is to be used in a Grade A and B area, the product
must be sterile.
The process of removing or destroying microorganisms and reducing them to an acceptable
level, efficacy is dependent on several factors. These are concentration, temperature,
time, soiling, mode of application and type of organism. The ideal disinfectant
kills all microorganisms, is non-corrosive, fast acting, safe and leaving no residue. It is
also compatible with other cleaning agents/disinfectants and available in a variety of
formats. Different disinfectants are effective against different types of organisms, so
check the biocidal claims made by the manufacturer.
On what type of surfaces will the cleaning agent be used is an important factor to look
at along with what format that is best suited. To avoid waste and cut costs, use of the
appropriate pack size such as wipes for sessional use in sterile areas (e.g. LAF, isolators);
large packs of tub wipes for areas where high volume usage is expected (e.g. transfer
disinfection). Keep in mind that bulk sterile concentrates are no longer sterile once
opened; unit dose concentrates ensure fresh sterile solution is used every time. Trigger
sprays: available in 500ml, 1L and 4L in a protected system ensuring the contents remain
sterile during use.
Small surfaces are typically treated by spraying and/or wiping and have significant variation
in techniques. BEST PRACTICE is to spray and wipe to ensure maximum bioburden
reduction and particulate removal, since microbes are killed by exposure to the disinfectant
and those that are not killed are physically removed from the surface due to the mechanical
action of wiping. Particulates are removed from the surface due to mechanical action.
Spraying onto a dry wipe shows significant variation in wetting of the wipe between
operators. However, results show lower levels of airborne alcohol expected in comparison
to surface spraying. It is ideal for flat, smooth surfaces (e.g. benches) and will prevent
biocides from pooling in crevices. Spraying onto a surface is likely to achieve a more
consistent surface coverage. Higher levels of airborne alcohol is expected in comparison
to spraying onto the wipe. It is ideal for small items and uneven surfaces, but can result in
pooling of biocides in crevices resulting in corrosion (not an issue with alcohol).
Use of impregnated wipes (without spraying) will significantly reduce operator exposure
to the biocide/alcohol. Also the use of a pre-impregnated wipe in conjunction with
spraying will result in maximum bioburden reduction.
Wipe in unidirectional over-lapping strokes (10–25%) and use slow, deliberate movements
so as not to generate particulates and minimise disruption to airflows. A careful
technique is required to maximise mechanical action and ensure good contact of the
surface with the biocide. The wipe should be folded to allow maximum surface usage and
ideally a fresh surface of the wipe should be used for each stroke. Keep in mind that the
order of wiping just as important as it is with mopping (back > front, top > bottom, cleanest >
Points to consider are that the wipe should be folded to roughly hand size (this will
vary depending on the size of your hand and the size of the wipe). How often the wipe
must be re-folded to expose a “clean” side will depend on how dirty the surface is and the
criticality of the surface. There is a potential for contamination from the used surface of
the wipe to be transferred to the gloved hand! Some customers prefer to use a small wipe
and not fold it all for use in for Grade A areas for this reason.
Ideally a fresh “side” of the wipe should be used for each stroke, but in practice this is
not cost effective or necessary for all applications. In reality cost must be balanced
against risk. Surface area to be covered by 1 stroke will depend on the criticality of the
surface. Staff training and SOPs should define company practice to ensure consistency
There is no such thing as a “particulate/lint free wipe”, however some grades of wipe
will shed more particulates that others – dependant on material of construction and method
of manufacture. Ensure that the wipe selected is compatible with the disinfectant/alcohol
in use. Wipes manufactured using chemical binders may not be compatible. Wipes should be single use – re-used wipes will degrade and shed more particulates each time they are re-processed. When disinfecting large surfaces the some basic principle apply: Kill of microbes due to exposure to biocide Physical removal of microbes due to mechanical action Removal of particulates due to mechanical action For this reason the spray system should ideally be used in conjunction with a mopping system (mopping can be used as the residue removal step). When using a single bucket system, the disinfectant/cleaning solution quickly becomes contaminated due to soiling reducing the efficacy of the solution, which is not suitable for use in a GMP environment. The double bucket system is a slight improvement on the single bucket system due to the addition of a waste bucket so the mop head is rinsed in “clean” solution. There is a declining use of this system in pharmaceutical industry. Using a triple bucket system the mop is dipped into “clean” solution, wrung out and applied to the surfaces. Then it is rinsed in middle bucket and wrung out into the waste. Use of disinfectant as a rinse agent is best practice as it avoids the potential for the solution in the front bucket to become diluted. Water may be used as a rinse agent to control cost. Note that some disinfectants are more sensitive to dilution than others, resulting is significant reduction in efficacy (e.g. phenol-based disinfectants). Concentration Exponents is a measure of the impact of biocide concentration on biocidal activity. Products with a relatively high concentration exponent are more susceptible to dilution errors. Biocides with a high concentration exponents rapidly loose efficacy when diluted. This is important for preparation of the disinfectant, as well as use. The rinse/disinfectant solutions and mop heads should be replaced when they become visibly dirty. Solutions/mops may be taken from a higher grade area/surface to a lower grade area/surface, but where it is necessary to control cross-contamination equipment should be dedicated to a specific area. To ensure consistency company procedures should define the maximum area to be mopped with one bucket of solution/mop head (with the proviso that the solution is replaced earlier if found to be visibility dirty). There is no such thing as a “particulate/lint free mop”, as some mops will shed more particulates that others – dependant on material of construction and method of manufacture. Ensure that the mop material is compatible with the disinfectant in use. Mop fabrics manufactured using chemical binders may not be compatible. Select the appropriate grade of mop for the task at hand – sterile mops for applying sterile solutions. Mops should be for single use as re-used mops will degrade and shed more particulates each time they are used. Pre-impregnated mop wipes avoid over-application, reduces operator exposure, there is no need for disinfectant preparation and associated costs, and there is no need to dispose of liquid. This can be ideal for small cleanrooms that may not have space for a bucket system. Regulatory requirement (EU GMP/ PIC/S Annex 1, USP <1072>) originally introduced due to concerns regarding the potential build-up of microbial resistance (as observed with antibiotics). No scientific evidence to date of resistance occurring due to lack of rotation in a cleanroom setting. Unlike the use of antibiotics, disinfectants are used at relatively high concentration on a relatively small population, therefore the selective pressure for mutation is reduced. Disinfectant rotational schemes are still recommended as they ensure that the full spectrum of microbicidal activity is maintained, without the need to continually use a sporicidal agents, which are traditionally unpleasant to use. It is recommended that a bactericide/fungicide be rotated with a sporicide. USP <1072> Antiseptics and Disinfectants: The rotation of an effective disinfectant with a sporicide is encouraged. It is prudent to augment the daily use of a bactericidal disinfectant with weekly (or monthly) use of a sporicidal agent. The daily application of sporicidal agents is not generally favoured because of their tendency to corrode equipment and because of the potential safety issues with chronic operator exposure. Other disinfection rotation schemes may be supported on the basis of a review of the historical environmental monitoring data. PhaMIG survey revealed that there is no industry standard for rotation. EM data should be used to justify the frequency – if EM is in control then the current frequency is appropriate. Frequency of detergent cleaning will depend on risk factors associated with area, such as the amount of traffic (e.g. material transfer airlocks and gowning rooms higher risk), nature of processes that occur in the area (e.g. washrooms or areas where powders are handled are higher risk) and type of biocides used (low residue disinfectants = lower risk) and whether rinsing is performed (traditional disinfectants without rinsing = high risk). Contact times is the time needed for the required level of kill to be achieved. A product may have different contact times depending on the target organisms (e.g. extended contact time for sporicidal action). Whether a “wet” contact time is required depends on how efficacy validation was performed. NOTE: the surface is not re-wetted during the contact time for EN 13697 testing. To achieve longer “wet” contact times re-wetting may be required. The surface does not need to be completely saturated. Alcohol is very fast acting, some customers have validated full bactericidal activity at > 1min contact. For some products (Glucoprotamin) microbial kill may continue after the surface has dried. Effective cleaning and disinfection is a critical part of contamination control and GMP and to achieve the maximum benefit it is necessary to select the right products and use them appropriately. Deciding on the appropriate technique requires a pragmatic approach balancing risk, practicality and overall benefit and in order to be effective a controlled and consistent technique must be employed. Simple processes encourage compliance and it is essential that cleaning staff know not only HOW to perform these techniques, but WHY.
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