Until recently, the manual IMS procedure was the only step in the approved Cryptosporidium method which had not been improved.
TCS Biosciences have now developed an automated IMS system, which uses an IMS test developed by ImmuCell Corporation, USA.
The Isolate® system not only eliminates the RSI risk associated with manual rocking, but also improves the repeatability of the IMS test by standardising the rocking action.
A further advantage of the Isolate® system is its ability to handle packed pellets up to 2ml, significantly reducing the need for split samples and multiple microscope slides.
In a study comparing the Isolate® system with a manual IMS test, samples from two sources, a treated upland water and a river water, were filtered and concentrated to give known packed pellet volumes. 10 ml aliquots of each concentrate were spiked with 100 flow-sorted Cryptosporidium oocysts and processed by IMS. Slides were stained and counted, and the counts were expressed as percentage recoveries.
Recovery of Cryptosporidium was significantly better using the Isolate® system, as seen in Tables 1 and 2.
|Table 1. Percentage recovery of Cryptosporidium from an upland treated water
|Table 2. Percentage recovery of Cryptosporidium from river water
Isolate® yielded more consistent results than the manual test, as evidenced by the narrower data ranges obtained. These results suggest that the manual rocking procedure is sensitive to variations in operator technique. This study also demonstrated that adjustments to the speed, angle and vigour of the automated rocking procedure had significant effects upon Cryptosporidium recoveries. Once these factors were optimised, consistency of recovery was enhanced.
The regulation of Cryptosporidium testing has been a success, resulting in improved laboratory performance and better standardisation of methodologies. The DWI is now implementing changes to encourage laboratories to evaluate new technology. By doing this, laboratories can expect to benefit from improvements in health & safety, working efficiencies and turnaround times.
Automation has improved several aspects of the Cryptosporidium method, including filter washing, sample concentration and detection. Now, by applying automation to IMS, further improvements to both standardisation and Cryptosporidium recovery have been achieved.