Evaluation of a continuous flow centrifuge for recovery of Cryptosporidium oocysts from large volume water samples

This study aimed to evaluate the continuous flow centrifuge (CF centrifuge) for recovering Cryptosporidium oocysts from water under realistic environmental conditions. This was achieved by taking 100 l samples from a water tank with known seeding and turbidity levels. Samples were concentrated and purified using percoll discontinuous gradients and stained using monoclonal antibody on polycarbonate membrane filters. The maximum percent recoveries were achieved at a flow rate of 0.75 l/min and centrifuge speed of 2900×g. When compared directly with cartridge filtration at a seeding level of 10 oocysts/l and low turbidity of 1 nephelometric turbidity unit (NTU), recoveries were 14.8 and 9.7% (n=3) for the CF centrifuge and cartridge filtration respectively. At a higher turbidity of 5 NTU, recoveries were 13.0 and 9.0% respectively. These differences were not significant but the CF centrifuge sample is faster, simpler and safer to process. Its integration into flow cytometry is also evaluated. The recovery of Giardia by CF centrifugation at 10 cysts/l and 5 NTU gave a mean recovery of 37.9%.