A Nested PCR Assay to Avoid False Positive Detection of the Microsporidian Enterocytozoon hepatopenaei (EHP) in Environmental Samples in Shrimp Farms.
Hepatopancreatic microsporidiosis (HPM) caused by Enterocytozoon hepatopenaei (EHP) is an important disease of cultivated shrimp. Heavy infections may lead to retarded growth and unprofitable harvests. Existing PCR detection methods target the EHP small subunit ribosomal RNA (SSU rRNA) gene (SSU-PCR). However, we discovered that they can give false positive test results due to cross reactivity of the SSU-PCR primers with DNA from closely related microsporidia that infect other aquatic organisms. This is problematic for investigating and monitoring EHP infection pathways. To overcome this problem, a sensitive and specific nested PCR method was developed for detection of the spore wall protein (SWP) gene of EHP (SWP-PCR). The new SWP-PCR method did not produce false positive results from closely related microsporidia. The first PCR step of the SWP-PCR method was 100 times (104 plasmid copies per reaction vial) more sensitive than that of the existing SSU-PCR method (106 copies) but sensitivity was equal for both in the nested step (10 copies). Since the hepatopancreas of cultivated shrimp is not currently known to be infected with microsporidia other than EHP, the SSU-PCR methods are still valid for analyzing hepatopancreatic samples despite the lower sensitivity than the SWP-PCR method. However, due to its greater specificity and sensitivity, we recommend that the SWP-PCR method be used to screen for EHP in feces, feed and environmental samples for potential EHP carriers.
Department of Biochemistry, Faculty of Science, Mahidol University, Bangkok, Thailand.|Center of Excellence for Shrimp Molecular Biology and Biotechnology (Centex Shrimp), Faculty of Science, Mahidol University, Bangkok, Thailand.
Pattana
P
Jaroenlak
Center of Excellence for Shrimp Molecular Biology and Biotechnology (Centex Shrimp), Faculty of Science, Mahidol University, Bangkok, Thailand.|Shrimp Pathogen Interaction Laboratory (SPI), National Center for Genetic Engineering and Biotechnology (BIOTEC), Bangkok, Thailand.
Piyachat
P
Sanguanrut
Biosciences, College of Life and Environmental Sciences, University of Exeter, Exeter, United Kingdom.
Bryony A P
BA
Williams
European Community Reference Laboratory for Crustacean Diseases, Center for Environment, Fisheries and Aquaculture Science (Cefas), Weymouth, Dorset, United Kingdom.
Grant D
GD
Stentiford
Center of Excellence for Shrimp Molecular Biology and Biotechnology (Centex Shrimp), Faculty of Science, Mahidol University, Bangkok, Thailand.|National Center for Genetic Engineering and Biotechnology (BIOTEC), National Science and Technology Development Agency (NSTDA), Pathum Thani, Thailand.
Timothy W
TW
Flegel
Shrimp Pathogen Interaction Laboratory (SPI), National Center for Genetic Engineering and Biotechnology (BIOTEC), Bangkok, Thailand.|National Center for Genetic Engineering and Biotechnology (BIOTEC), National Science and Technology Development Agency (NSTDA), Pathum Thani, Thailand.
Kallaya
K
Sritunyalucksana
Department of Biochemistry, Faculty of Science, Mahidol University, Bangkok, Thailand.|Center of Excellence for Shrimp Molecular Biology and Biotechnology (Centex Shrimp), Faculty of Science, Mahidol University, Bangkok, Thailand.
Ornchuma
http://orcid.org/0000-0003-0371-3877
O
Itsathitphaisarn
D000818:Animals; D001483:Base Sequence; D004271:DNA, Fungal / Q000032:analysis* / Q000235:genetics; D021862:Enterocytozoon / Q000235:genetics / Q000302:isolation & purification*; D005398:Fisheries; D017403:In Situ Hybridization; D016881:Microsporidiosis / Q000382:microbiology* / Q000662:veterinary*; D033561:Penaeidae / Q000382:microbiology*; D016133:Polymerase Chain Reaction / Q000379:methods; D016415:Sequence Alignment; D012758:Shellfish / Q000382:microbiology*
D004271:DNA, Fungal