الفهرس 
AcknowledgmentOnly 14 pages are availabe for public view
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Abstract
In our study, a molecular beaconbased reverse transcriptase polymerase chain reaction (MBRTPCR) assay was developed for realtime detection of HAV particles. Molecular beacons are singlestranded oligonucleotide probes that form a stemloop structure that fluoresce upon hybridization to their targets. The sensitivity of the realtime RTPCR assay using KH1 and KH2 primers in the presence of the designed molecular beacon was evaluated using serial tenfold dilutions of vial RNA of HAV. As low as 1.0 (Plaque Forming Unit) PFU of the viral RNA was detected. The selectivity of the assay relies on the selected sequence of the primer set and the probe moiety. Different organisms were tested using our assay. The results of our experiments showed that none of the other enteric viruses or phages tested produced any significant fluorescence. An alternative to RTPCR that is potentially applicable to the detection of RNA viruses is the nucleic acid sequence based amplification (NASBA) technique. NASBA is an isothermal nucleic acid amplification method that is particularly suited to RNA targets. A NASBA assay in combination with molecular beacon was developed for the realtime detection and quantification of Hepatitis A virus (HAV). By combining the capability of immunomagnetic separation (IMS) to concentrate HAV, separate the viruses from inhibitory substances, and recover target RNA using only a simple heating step followed by molecular beaconreverse transcription polymerase chain reaction (MBRTPCR), a detectable signal was obtained up to 20 PFU. These observations further confirm the potential use of the combined IMS/MBRTPCR assay as a simple tool for rapid detection and quantification of HAV from environmental samples. In the same way, we were able to use the same technique for detecting the virus in intentionally contaminated food samples by spiking some vegetables and fruits with the virus and collecting it using IMS technique followed by MBRTPCR. A detection signal was obtained at 25 PFU dilution of the virus.