Development and evaluation of a real-time PCR assay for quantification of Giardia and Cryptosporidium in sewage samples

Cryptosporidium and Giardia are major causes of diarrheal disease in humans worldwide and are major causes of protozoan waterborne diseases. Two DNA TaqMan PCR-based Giardia and Cryptosporidium methods targeting a 74-bp sequence of the beta-giardin Giardia gene and a 151-bp sequence of the COWP Cryptosporidium gene, respectively, were used as models to compare two different LNA/DNA TaqMan probes to improve the detection limit in a real-time PCR assay. The LNA probes were the most sensitive resulting in 0.96 to 1.57 lower C (t) values than a DNA Giardia TaqMan probe and 0.56 to 2.21 lower than a DNA Cryptosporidium TaqMan probe. Evaluation of TaqMan Giardia and Cryptosporidium probes with LNA substitutions resulted in real-time PCR curves with an earlier C (t) values than conventional DNA TaqMan probes. In conclusion, the LNA probes could be useful for more sensitive detection limits.