Detection of Echinococcus granulosus and Echinococcus multilocularis in cyst samples using a novel single tube multiplex real-time polymerase chain reaction

Abstract

Cystic echinococcosis (CE) and alveolar echinococcosis (AE) caused by Echinococcus granulosus and Echinococcus multilocularis, respectively, are important helminthic diseases worldwide as well as in our country. Epidemiological studies conducted in Turkey showed that the prevalence of CE is 291-585/100.000. It has also been showed that the seroprevalence of AE is 3.5%. For the diagnosis of CE and AE, radiological (ultrasonography, computed tomography, magnetic resonance) and serological methods, in addition to clinical findings, are being used. The definitive diagnosis relies on pathological examination When the hydatid cysts are sterile or does not contain protoscolex, problems may occur during pathological discrimination of E.granulosus and E.multilocularis species. In this study, we aimed to develop a novel multiplex real-time polymerase chain reaction (M-RT-PCR) targeting mitochondrial 12S rRNA gene of E.granulosus and E.multilocularis using Echi S (5'-TTTATGAATATTGTGACCCTGAGAT-3') and Echi A (5'-GGTCTTAACTCAACTCATGGAG-3') primers and three different probes; Anchor Ech (5'-GTTTGCCACCTCGATGTTGACTTAG-fluoroscein-3'), Granulosus (5'-LC640-CTAAGGTTTTGGTGTAGTAATTGATATTTT-phosphate-3') and Multilocularis (5'-LC705-CTGTGATCTTGGTGTAGTAGTTGAGATT-phosphate-3') that will enable the diagnosis of CE and AE in same assay. During M-RTR-PCR, plasmids containing E.granulosus (GenBank: AF297617.1) and E.multilocularis (GenBank: NC_000928.2) mitochondrial 12S rRNA regions were used as positive controls. Cysts samples of patients which were pathologically confirmed to be CE (n: 10) and AE (n: 15) and healthy human DNA samples (n: 25) as negative control as well as DNA samples of 12 different parasites (Taenia saginata, Hymenolepis nana, Trichuris trichiura, Fasciola hepatica, Enterobius vermicularis, Toxoplasma gondii, Pneumocystis jirovecii, Trichomonas vaginalis, Cryptosporidium hominis, Strongyloides stercoralis, Plasmodium falciparum, Plasmodium vivax) were used to develop M-RT-PCR. E.granulosus and E.multilocularis control plasmids were constructed to detect analytic sensitivity of the test using TOPO cloning. Positive control plasmids were diluted to determine analytical sensitivity and specificity by distilled water at 10(6)-10(5)-10(4)-10(3)-10(2)-10(1)-1 plasmid copy of dilution in each reaction. According to the results, analytical sensitivity of the assay for E.granulosus and E.multilocularis was 1 copy plasmid/µl reaction. The non-existence of cross reactivity with 12 different parasites' DNA samples showed the analytical specificity of the assay. Displaying Echinococcus DNA in cyst samples among 25 patients and species discrimination as well as non-existence of cross reactivity with human DNA samples showed that the clinical sensitivity and specificity of the assay were 100%. As a result, the M-RT-PCR developed in the present study provided a sensitive, specific, rapid, and reliable method in the diagnosis of echinococcosis and the discrimination of E.granulosus and E.multilocularis from cyst samples.