David Fegredo
Medical Scientist
PathWest
Australia
Recently, we have begun to use adhesive mats to prevent contamination from human DNA and cellular material as workers and/or transport items enter into our PCR laboratory. As our laboratory analyzes human DNA, it is important that we use as many measures as possible to reduce contamination in “clean” and DNA prep rooms, including a one-way linear laboratory with separate rooms and a variety of appropriate accessories. There are problems associated with some of the products available for maintaining an uncontaminated environment and decontamination of the lab. Extensive use of bleach on the floors and benches produces a very strong odor and can be hazardous to your health if exposed to it for long periods of time. Overhead UV lighting causes degradation of plastic material, some of which can be quite expensive such as entire pipette sets, computer monitor casings etc. Thus better alternatives or added measures are needed. One such alternative is the BACS sticky floormat to assist in preventing some contamination in DNA laboratories.
BACS IT Protection, located in Australia, produces a relatively inexpensive product that consists of 30 1.2mm thick sheets of adhesive film that are rectangular in shape and long enough to ensure that anyone entering or exiting a room must step on the mat with both feet and the wheels of transport vehicles rotate at least one time in order to clean each wheel. As each mat loses its adhesiveness it should be pulled up and disposed of appropriately. Each of the 30 sheets is numbered and removal is easiest when pulled from the number tag. The composition of the sheets is unknown as it is a proprietary product. The mats have an adhesive undersurface so that they can be fixed to the floor in the desired area. They do not possess a bevelled edge frame like many of their competitors thus eliminating occupational health and safety issues. Because the mats are so thin doors can even be opened over them without any problems.
In order to test the effectiveness of these mats I excised a 10mm˛ section of a dirty mat from the middle to avoid contamination from people who remove the used sheets . Then I performed a standard Chelex DNA extraction on the excised section. Quantifiable human DNA was detected suggesting that the mats were effective at trapping contaminants. In addition, DNA profiling showed numerous distinct alleles at all of the loci in the assay we use indicates that DNA from at significant number of people had been trapped on the way into the “clean” areas of the laboratory and a smaller amount of DNA on the way out of the “dirty” areas. The results showed that these mats can be useful in preventing some human DNA or cellular material shed from staff from potentially contaminating laboratories. These mats are only one part of contamination prevention strategies and do not provide protection against contaminated consumables such as pipette tips, reagent bottles etc. The usual PCR lab protocols for prevention of contaminated items going into inappropriate rooms should always be observed.
