To do this requires a pump that is easy and quick to use, does not require cleaning or maintenance, and guarantees no cross-contamination between samples. Peristaltic pumping technology from Watson-Marlow was adopted to achieve this objective.
Each Pathatrix system consists of five independent testing stations within one housing, with five Watson-Marlow 313D-series pumpheads per machine. The tubing in the pumphead is only ever used for one sample, thereby eliminating the risk of cross-contamination.
"One of the benefits of the Pathatrix system is that it needs only around two minutes of hands-on time, and the 313D pumphead's flip-top design and automatic tube tensioning are perfect in this respect," said Dr Adrian Parton, Matrix Microscience managing director.
Furthermore, with the tubing made from a compliant silicone rubber, the instruments are capable of analysing an extremely wide variety of food samples, from milk and yoghurt to acidic products and solid samples - such as ground beef - that are homogenised with the 225 ml of liquid growth media.
Another element of the recirculated medium is the Pathatrix capture reagent, which consists of magnetic particles that are coated with an antibody specific to the target pathogen. Once loaded, the Pathatrix workstation runs for 180 minutes at the desired incubation temperature - from 30 to 37 degrees C - with the Watson-Marlow pump circulating the fluid within a closed loop to ensure complete incubation.
After the incubation step is finished, the target microorganisms, now captured by the reagent, are magnetically restrained while the residual debris and other unwanted material is removed when the peristaltic pump operates again for the wash step.
The capture phase is then removed from the system and is further processed so that pathogen colonies can be viewed within 16 hours of the start of the analysis. This is a significant saving compared with the two days or so that is usually required, and there is an additional benefit in that the sample is not contaminated with non-target organisms.
Matrix Microscience claims that independent tests have shown the Pathatrix system to be 221 per cent more sensitive than the standard USDA FSIS (United States Department of Agriculture, Food Safety and Inspection Service) method, as well as being quicker and requiring only minimal hands-on time, unlike the labour-intensive alternatives. As a result of the tests undertaken at Campden & Chorleywood Food Research Association, the Pathatrix system has now received AOAC (Association of Official Analytical Chemists) R1 Validation.
Whereas the food standards in USA are driven by the USDA FSIS, there is no equivalent body in the UK. Instead, the supermarket chains tend to lay down their own quality standards, including zero tolerance for certain pathogens, which is understandable, because Listeria, Salmonella and E. coli can all be fatal for vulnerable groups such as the young, elderly and infirm.
Furthermore, with many perishable fresh foods having a short shelf life - sandwiches are a good example - there is a need for cost-effective, rapid testing. Matrix Microscience has therefore developed its state-of-the-art Pathatrix system to meet the demands of the supermarket chains, as well as food manufacturers, livestock breeders and contract laboratories.