Polymeric flooring versus peel-off mats
Dr Caroline Clibbon evaluates the effectiveness of polymeric flooring compared with peel-off mats
Dr Caroline Clibbon evaluates the effectiveness of polymeric flooring compared with peel-off mats
To maintain the highest levels of cleanliness within a cleanroom environment, GMP and quality assurance demand that particle and microbiological contamination levels within any critical area should be minimised to prevent contamination of the product.This paper compares two different types of floor covering used to reduce foot- and wheel-borne contamination - the peel-off/acrylic mat and polymeric floor covering - the aim being to minimise the presence of both viable and non-viable contamination, before entering cleanroom conditions.
cost considerations
It is recognised that both foot- and wheel-borne contamination are two major sources of both viable and non-viable contamination. Therefore, control and preferably elimination of entry of these particles into cleanroom areas is of paramount importance as particulate contamination affects yield, quality, productivity and cost. Studies of current practice suggest that this type of contamination can reduce product yield by as much as 20%.
Since people are a major source of contamination through body regenerative processes, operator behaviour and work habits, particulates can be readily transferred into critical cleanroom environments from operators' footwear or from inanimate objects, such as wheels, materials or equipment. Therefore to minimise particulate contamination, some form of floor anticontamination system is required, since it is easier and less expensive to control foot- and wheel-borne contamination prior to the critical environment.
The study was performed within the Pharmaceutical Microbiology Unit (PMU) at GlaxoSmithKline's r&d facility in Ware, Hertfordshire. Dycem's polymeric floor covering was placed for a trial period within the corridor area at the entrance to the cleanroom facility. The clean room is used primarily for water testing within the unit at Ware.
contaminant levels
The two types of flooring, polymeric flooring and the peel-off mat, were evaluated using a swabbing technique. Levels of contaminants were determined before contact with the floors to determine base values. Swabs were moistened with sterile 0.9% peptone water and samples taken from trolley wheels. Each sample was approximately one half of a wheel circumference. In addition, the soles of operators' footwear, wearing overshoes at the entry to the corridor area of the PMU clean suite, were also swabbed with the peptone water before contact with the flooring or the mat.
The swabs were plated out onto Tryptone Soya Agar(TSA) plates for bacteria and Sabouraud's Dextrose Agar(SDA) plates for yeasts and moulds, and incubated at 30 to 35°C for three to five days and at 20 to 25°C for five to seven days respectively.
The procedure was repeated with swabs being taken from two wheels from each trolley after being pushed across the polymeric floor covering or the peel-off mat. The remaining half of the trolley wheel was also swabbed.
In addition, swabs were taken from operators' footwear after walking across either type of floor covering and making at least four imprints onto the flooring. The surface swabs were plated out using the procedure described previously.
high values
The experimental investigation was performed under test conditions comparable with those used in practice.
The length of flooring allowed for a minimum of at least four imprints or foot falls (i.e. two imprints for each foot) onto the flooring and also four rotations of trolley wheels. Surface swabs were taken using overlapping strokes to obtain maximum recovery.
The acceptance criteria for this investigation were to demonstrate a reduction in the microbial count for wheel- and foot-borne contamination after contact with the flooring and compare the results with those obtained from peel-off mats.
The averaged and mean percentage reduction values were calculated and are shown in Tables 1 and 2. The mean percentage reduction values for the polymeric flooring were 99.4% for TSA plates and 100% for SDA plates for wheel-borne contamination and 99.8% for TSA and SDA plates for foot-borne contamination.
In contrast, the mean percentage reduction values after contact with the peel-off mats were much lower for both contamination types. For wheel-borne contamination the values were 25.2% for TSA plates and 27.15% for SDA plates, and 11.5% for TSA plates and 15% for SDA plates for foot-borne contamination.
effective flooring
Graphical representation of mean viable counts for contamination using TSA and SDA are shown in Figures 1 and 2 respectively.
This investigation has demonstrated that polymeric flooring is far more effective in controlling microbiological contamination than peel-off mats for both wheel- and foot-borne contamination. Indeed, the flooring is highly effective in controlling microbiological contamination of both bacteria and yeasts/moulds from operators' footwear and trolley wheels.
Further investigative work is required to assess the minimum number of foot prints required to achieve an effective reduction of microbiological contamination from operators' footwear after contact with flooring.
In addition, further studies would be appropriate to determine the minimum amount of contact for trolley wheels with the flooring to reduce or control microbiological contamination of both viable and non-viable particles into the cleanroom.
Peptone water
Peptone water is a culture medium. The nutrient-rich broth produces high resuscitation rates for subletally injured bacteria and intense growth. A phosphate buffer system prevents bacterial damage due to changes in the pH of the medium.