Application of reverse transcriptase-nested-PCR for detection of poliovirus in mussels

Vidas UP-enzyme-linked fluorescent immunoassay based on recombinant phage protein and fluorescence in situ hybridization as alternative methods for detection of Salmonella enterica serovars in meat

Several methods for the rapid and specific detection of Salmonella spp. in meat have been described. This study was conducted to evaluate the capability of the VIDAS(®) UP (SPT [Salmonella Phage Technology]), an enzyme-linked fluorescent immunoassay method, and fluorescence in situ hybridization (FISH) to complement the International Organization for Standardization Method 6579 (ISO) in detecting Salmonella spp. from beef, pork, and poultry meat samples. The meat was inoculated with a mixture of Salmonella spp. on three levels of contamination. It was also checked that the tests did not produce cross-reactions with other Enterobacteriaceae rods. On the basis of the results, the relative specificity, relative accordance, and relative sensitivity of the method were determined. In meat samples, Vidas UP and FISH detection results were in substantial agreement with ISO, with relative specificity, accordance, and sensitivity rates of 90%, 96.3%, and 100%, respectively, for Vidas UP and 100%, 100%, and 99.4%, respectively, for FISH. This is the first report on the evaluation of both Vidas UP and FISH compared to ISO for the rapid detection of Salmonella enterica serovars in meat.

A decade with nucleic acid-based microbiological methods in safety control of foods

In the last decade, nucleic acid-based methods gradually started to replace or complement the culture-based methods and immunochemical assays in routine laboratories involved in food control. In particular, real-time polymerase chain reaction (PCR) was technically developed to the stage of good speed, sensitivity and reproducibility, at minimized risk of carry-over contamination. Basic advantages provided by nucleic acid-based methods are higher speed and added information, such as subspecies identification, information on the presence of genes important for virulence or antibiotic resistance. Nucleic acid-based methods are attractive also to detect important foodborne pathogens for which no classical counterparts are available, namely foodborne pathogenic viruses. This review briefly summarizes currently available or developing molecular technologies that may be candidates for involvement in microbiological molecular methods in the next decade. Potential of nonamplification as well as amplification methods is discussed, including fluorescent in situ hybridization, alternative PCR chemistries, alternative amplification technologies, digital PCR and nanotechnologies.

Prevalence of hepatitis A virus in sea food in Iran

The objective of this study was to determine the prevalence of Hepatitis A Virus (HAV) in sea food samples in the Isfahan and Shahrekord townships in Iran. From September 2010 to April 2011, a total of 300 samples of fresh fish, shrimp, crab and lobster were obtained from randomly selected retail stores in the Isfahan and Shahrekord townships in Iran. The samples were tested for the presence of HAV using a reverse transcriptase- polymerase chain reaction method. Out of the total number of samples examined, 8 (2.7%) were found to be positive for HAV. This virus was detected in 5% and 1.7% of fresh fish and shrimp, respectively. This study shows the importance of sea food as potential sources of HAV infection in people in Iran.

A sensitive and reliable reverse transcriptase PCR-enzyme-linked immunosorbent assay for the detection of human pathogenic viruses in bivalve molluscs

A colorimetric method, reverse transcriptase PCR with an enzyme-linked immunosorbent assay (RT-PCR-ELISA) was evaluated for ease of use, reliability, and sensitivity when detecting known human pathogenic virus present in shellfish, using a traditional polyethylene precipitation or immunocapture virus concentration method. The newly developed ELISA method could successfully detect enteroviruses and noroviruses in artificially and naturally contaminated shellfish. Overall, ELISA was shown to be a robust and sensitive method, which had a detection limit of 10 to 100 50% tissue culture infective dose enterovirus per gram of Crassostrea gigas (Pacific oyster) digestive gland and whole Mytilus edulis (common blue mussel). The technique was easily established in a new laboratory and required no specialized equipment. The method had a high sample throughput capable of screening 96 samples per run, making the technique extremely time efficient. RT-PCR-ELISA is a safe, quick, reliable technique, which has the potential for use as a standard virus detection method.

Diversity of enterovirus sequences detected in oysters by RT-heminested PCR

Oysters harvested in western France, from five sites associated with outbreaks of food-borne norovirus gastroenteritis between February 2000 and March 2001, were assayed for enterovirus RNA by reverse transcriptase-heminested polymerase chain reaction (RT-heminested PCR). Forty percent (21/52) of shellfish samples (pool of seven oysters) were contaminated by enteroviruses. Infectious coxsackieviruses serotype A21 were isolated from three of these positive samples. Amplicons corresponding to 65 base sequences in the 5' untranslated region of the enteroviral genome were analyzed by direct sequencing. Interpretable results were obtained from 18 amplicons, but mixtures of sequences confused the results from 3 samples. Sequences isolated from samples from the different sites were different but similarities were observed between sequences detected in shellfish from two sites at different dates. Sequences were also compared to sequences of human, bovine and porcine enteroviruses. Both human and animal origins of enterovirus contamination of shellfish seemed likely.

Detection of hepatitis A virus in shellfish (Mytilus galloprovincialis) with RT-PCR

A PCR assay for the detection of hepatitis A virus (HAV) in shellfish is described. The procedure involves the concentration of viral particles with the use of polyethylene glycol (PEG), followed by viral RNA extraction and purification with oligo(dT) cellulose. Reverse transcriptase-PCR detection was accomplished in a single step with the use of primers specific for the VP3-VP1 region of the genome. The procedure detected one 50% tissue culture infective dose (0.6 PFU) per 25 g of shellfish homogenate. Heminested PCR was then carried out to verify the specificity of the PCR products. The method was used to detect HAV in shellfish samples from EU categories B and C and to evaluate the quality of shellfish in routine monitoring for HAV in view of the relevant public health implications of this foodborne disease.

Three-year study to assess human enteric viruses in shellfish

The main pathogenic enteric viruses able to persist in the environment, such as hepatitis A virus (HAV), Norwalk-like virus (NLV), enterovirus (EV), rotavirus (RV), and astrovirus (AV), were detected by reverse transcription-PCR and hybridization in shellfish during a 3-year study. Oyster samples (n = 108), occasionally containing bacteria, were less frequently contaminated, showing positivity for AV (17%), NLV (23%), EV (19%), and RV (27%), whereas mussel samples, collected in areas routinely impacted by human sewage, were more highly contaminated: AV (50%), HAV (13%), NLV (35%), EV (45%), and RV (52%). Sequences obtained from HAV and NLV amplicons showed a great variety of strains, especially for NLV (strains close to Mexico, Snow Mountain Agent, or Norwalk virus). Viral contamination was mainly observed during winter months, although there were some seasonal differences among the viruses. This first study of virus detection over a fairly long period of time suggests that routine analysis of shellfish by a molecular technique is feasible.

Determination of enteroviruses, hepatitis A virus, bacteriophages and Escherichia coli in Adriatic Sea mussels

The aim of the present study was to evaluate the incidence of enteric viruses in mussels and to verify the possibility of using phages as indirect indicators of mussel viral contamination. Mussels (36 samples) collected from three different areas of the Adriatic Sea were analysed to determine the following parameters: Escherichia coli, somatic coliphage (T6 phage), F-Plus (MS2 phage), B40-8 (phage of Bacteroides fragilis), enteroviruses and hepatitis A virus. Most of the results of the bacteriological analysis (most probable number (MPN) ml-1) were in accordance with the bacteriological limits established by European law, with the exception of seven samples. The bacteriophage analyses were always negative for F-Plus and B40-8, with the exception of a few samples, whereas the somatic coliphages were generally between 0 and 20 MPN g-1, with the exception of two samples (110 MPN g-1). The virological analysis showed five samples positive for the presence of enteroviruses and 13 for the presence of hepatitis A virus (in three samples both viruses were present). Most of these samples presented acceptable bacteriological parameters and the bacteriophages were absent or their value was generally very low. The results show that the detection of E. coli and phages does not seem to be a good indicator of viral contamination.