New rapid test for diarrhoea-causing bug

Identifying individual species of Cryptosporidium

Source of Article:  http://www.tcetoday.com/tcetoday/NewsDetail.aspx?nid=11270

by Wendy Laursen








THE TIME TAKEN to identify the diarrhoea-causing microorganism Cryptosporidium in water samples has been reduced from 15 hours to three, and the new technique enables the most harmful species to be identified so that sources of contamination can be more readily identified.


The technology is based on the detection of the Cryptosporidium species usually found in human faeces using fluorescent probes that target specific sequences of nucleic acid. Existing immuno-chromatographic and immuno-fluorescence-based assays do not provide species or genotype-specific information and polymerase chain reaction techniques involve expensive equipment and reagents.


“The probes can distinguish C. parvum and C. hominis which are responsible for most of the outbreaks that are harmful to humans,” says Anitha Alagappan, test developer and a PhD candidate at Australia’s Environmental biotechnology Cooperative Research Centre.


“Species data is important to understand the risk of infection to exposed people. There are many different species of Cryptosporidium, some of which are infectious to humans and some which aren’t. Many current testing methods only detect the presence or absence of Cryptosporidium, but not the species of concern.”


The new rapid screening tool uses fluorescent in situ hybridisation technology. The reliability of the new technology was tested against one of the standard methods applied in the water industry in collaboration with the Cryptosporidium Reference Laboratory in the UK. A strong correlation (0.994) between the two methods confirmed that the species identification method was as reliable as currently-used methods.


“The test has been validated now and could be used by water utilities worldwide as it fits into current testing methods quite easily,” says Belinda Ferrari team leader from the University of New South Wales.


The diarrhoeal illness, cryptosporidiosis, can be life threatening in immuno-compromised people and currently there is no effective treatment. Public swimming pools and drinking water have been sources of the disease in the UK and the US.





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