Comparative evaluation of new TaqMan real-time assays for the detection of hepatitis A virus

Crystal digital RT-PCR for the detection and quantification of norovirus and hepatitis A virus RNA in frozen raspberries

Berries are important vehicles for norovirus (NoV) and hepatitis A virus (HAV) foodborne outbreaks. Sensitive and quantitative detection of these viruses in food samples currently relies on RT-qPCR, but remains challenging due to their low concentration and the presence of RT-qPCR inhibitors. Moreover, quantification requires a standard curve. In this study, crystal digital RT-PCR (RT-cdPCR) assays were adapted from RT-qPCR sets of primers and probe currently used in our diagnostic laboratory for the detection and precise quantification of norovirus genogroups I and II (NoV GI, GII) and hepatitis A virus (HAV) RNA in frozen raspberry samples. We selected assay conditions based on optimal separation of positive and negative droplets, and peak resolution. Using virus-specific in vitro RNA transcripts diluted in raspberry RNA extracts, we showed that all three RT-cdPCR assays were sensitive, and we estimated the 95 % detection limit at 9 copies per RT-cdPCR reaction for NoV GI, 3 for NoV GII, and 14 for HAV. Serial dilutions of the RNA transcripts showed excellent linearity over a range of four orders of magnitude. We achieved precise quantification (CV ≤ 35 %) of the RNA transcripts between runs down to 15-145 copies per reaction for NoV GI, <20 for NoV GII, and < 15 for HAV. The three RT-cdPCR assays also proved to be tolerant to inhibitors from frozen raspberries, although not as tolerant as the RT-qPCR assays in the case of NoV GI and HAV. We further evaluated the assays with inoculated frozen raspberry samples and compared their performance to that of the RT-qPCR assays. As compared to the corresponding RT-qPCR assays, the NoV GI and HAV RT-cdPCR assays showed a decreased qualitative sensitivity, while the NoV GII RT-cdPCR assay had an increased sensitivity. As for quantification, the NoV GI and NoV GII RT-cdPCR assays produced similar estimates of RNA copy number than their respective RT-qPCR assays, whereas for HAV, the RT-cdPCR assay produced lower estimates than the RT-qPCR assay. However, all the RT-cdPCR assays provided more precise quantitative measurements at low levels of contamination than the RT-qPCR assays. In conclusion, the potential of the RT-cdPCR assays in this study to detect viral RNA from frozen raspberries varied according to assay, but these RT-cdPCR assays should be considered for precise absolute quantification in difficult matrices such as frozen raspberries.

Norovirus GI and GII and hepatitis A virus in berries and pomegranate arils in Canada

Between 2016 and 2021, the Canadian Food Inspection Agency (CFIA) collected 4218 samples of fresh and frozen berries (blackberries, blueberries, raspberries, strawberries and mixed berries) and pomegranate arils at retail across 11 major cities in Canada and tested these samples for the presence of norovirus GI, norovirus GII and hepatitis A virus RNA. The purpose of this testing was to provide information on the prevalence of these viruses in berries and pomegranate arils on the Canadian marketplace. Of the 926 fresh fruit samples tested, norovirus GI RNA was detected in one raspberry sample and norovirus GII RNA was detected in one strawberry sample. Of the 3292 frozen fruit samples tested, norovirus GI RNA was detected in one blackberry sample, one raspberry sample and one strawberry sample, and norovirus GII RNA was detected in one blueberry sample, three raspberry samples, four strawberry samples, one pomegranate arils sample and one mixed berry sample. None of the fresh or frozen fruit samples tested positive for hepatitis A virus RNA. No statistically significant associations were observed between the prevalence of viral RNA in samples of fresh and frozen fruit, between the prevalence of viral RNA in samples of domestic and imported fruit or between the prevalence of viral RNA in samples of specific fruit types. Overall, the prevalence of norovirus GI and GII RNA together in fresh and frozen fruit samples in Canada was 0.36 %. The results of this study may be used to refine surveillance programs for norovirus and hepatitis A virus in fresh and frozen berries and pomegranate arils, e.g. by adapting the commodities tested and/or the numbers of planned samples to better target these hazards. This information may also be used to inform other Government of Canada approaches to better understand the controls associated norovirus and hepatitis A virus in fresh and frozen berries and pomegranate arils.

Implementing sequencing-based surveillance in developing countries: findings from a pilot rollout for hepatitis A in China

Background

The emergence of SARS-Cov2 variants has highlighted the need to implement sequencing-based surveillance in developing countries for early response to mutant viruses of concern. However, limited information on how to implement sequencing-based surveillance is available, and the feasibility and performance of this new type of surveillance are still in question.

Methods

To understand the challenges with the implementation and to promote sequencing-based surveillance, we reported findings from a pilot for hepatitis A (HepA) in five sentinel provinces in China as an example of sequencing-based surveillance implementation. The performance of the surveillance system was evaluated by indicators related to acceptability, data quality, simplicity, utility, and timeliness. We use a scale from 1 to 3 was used to provide a score for each aspect.

Results

During the pilot, 306 cases of HepA were reported, and 49.79% of samples were available for sequencing. Eleven genomic clusters were found, of which seven clusters were potentially related to a foodborne outbreak oyster based on identical viral sequence and epidemiologic investigations. The greatest strength of the system was its simplicity (Score: 2.63). The acceptability (Score: 2.0) and utility (Score: 2.33) were modest, but data quality (Score: 1.75) and timeliness (Score: 1.75) were the main challenges.

Conclusions

Overall, the system performed satisfactorily and proved to be useful for virological characterization of cases and early outbreak detection, with a great potential for scale-up. Further efforts are required to address financial and human resource constraints and inadequate support among physicians. Education should be given to health care professionals to improve the data quality. The establishment of decentralized surveillance networks can be an approach to improve timeliness for emerging infections.

Persistence of murine norovirus, bovine rotavirus, and hepatitis A virus on stainless steel surfaces, in spring water, and on blueberries

The viability of murine norovirus (MNV-1), bovine rotavirus (boRV), and hepatitis A virus (HAV) was evaluated at 21 °C, 4 °C, and -20 °C on stainless steel surfaces, in bottled water, and on blueberries for up to 21 days. After 14 days of incubation at 21 °C on stainless steel, a viability loss >4 log for MNV-1, >8 log for boRV, and >1 log for HAV was observed. Losses were observed for MNV-1 (>1 log) and HAV (>2 log) incubated in water at 21 °C for 21 days. No significant loss was detected for MNV-1 and HAV at 4 °C and -20 °C and for boRV at 21 °C, 4 °C, and -20 °C. On blueberries incubated at 4 °C and -20 °C, they all maintained their infectivity. After 7 days at 21 °C, a loss >2 log, a loss of 3 log, and no loss were observed for boRV, MNV-1, and HAV, respectively. After RNase pretreatment, the detection of extracted RNA from infectious and noninfectious samples suggested the protection of RNA inside the capsid. Even though they all are enteric viruses, their persistence varied with temperature and the nature of the commodity. It is therefore important to use more than one viral surrogate, during inactivation treatments or implementation of control measures.

Hepatitis A Outbreak in the General Population due to a MSM-Associated HAV Genotype Linked to a Food Handler, November 2017-February 2018, Germany

Hepatitis A (HAV) is a viral infection causing a range of symptoms, sudden onset of fever, malaise, diarrhea, and jaundice. It is mostly transmitted fecal-oral through contaminated food, with immediate household and sexual contacts having a higher risk of infection. Since 2016 an increased number of HAV infections, mostly affecting men who have sex with men (MSM) have been noticed worldwide, with three main genotypes circulating. We report here on the first spillover outbreak of the MSM-associated HAV genotype RIVM-HAV16-090 in the German general population in November 2017-February 2018. In total, twelve cases could be attributed to the outbreak with the index case and a coworker in a butchers shop being the most probable source of the outbreak. The identical HAV genotype was detected in two environmental samples in the premises of the butchers shop and in nine cases. Outbreak control measures included detailed contact tracing and stool examinations, several environmental investigations, thorough cleaning, and disinfection of the premises of the butchers shop. Post-exposure vaccination was recommended to all unprotected contacts during the investigation. Furthermore, although hand-washing facilities were in accordance with the required law, additional installment of soap and disinfectant dispensers and contactless faucets has been recommended.

Prevalence and evaluation strategies for viral contamination in food products: Risk to human health-a review

Nowadays, viruses of foodborne origin such as norovirus and hepatitis A are considered major causes of foodborne gastrointestinal illness with widespread distribution worldwide. A number of foodborne outbreaks associated with food products of animal and non-animal origins, which often involve multiple cases of variety of food streams, have been reported. Although several viruses, including rotavirus, adenovirus, astrovirus, parvovirus, and other enteroviruses, significantly contribute to incidence of gastrointestinal diseases, systematic information on the role of food in transmitting such viruses is limited. Most of the outbreak cases caused by infected food handlers were the source of 53% of total outbreaks. Therefore, prevention and hygiene measures to reduce the frequency of foodborne virus outbreaks should focus on food workers and production site of food products. Pivotal strategies, such as proper investigation, surveillance, and reports on foodborne viral illnesses, are needed in order to develop more accurate measures to detect the presence and pathogenesis of viral infection with detailed descriptions. Moreover, molecular epidemiology and surveillance of food samples may help analysis of public health hazards associated with exposure to foodborne viruses. In this present review, we discuss different aspects of foodborne viral contamination and its impact on human health. This review also aims to improve understanding of foodborne viral infections as major causes of human illness as well as provide descriptions of their control and prevention strategies and rapid detection by advanced molecular techniques. Further, a brief description of methods available for the detection of viruses in food and related matrices is provided.

Hepatitis A virus infections and outbreaks in asylum seekers arriving to Germany, September 2015 to March 2016

From September 2015 to March 2016, hepatitis A notifications in Germany increased by 45% to 699 cases compared to 482 cases in the same period of the previous year. Children aged five to nine years were predominantly affected (22% of all cases in this period). We hypothesized that this increase could be explained by the marked influx of asylum seekers in this time period. We analysed national surveillance data and estimated the number of imported and autochthonous hepatitis A cases in asylum seekers. We also investigated molecular signatures of hepatitis A viruses sampled from asylum seekers to identify chains of transmission. We found that 40% (278 cases) of all 699 hepatitis A cases notified between September 2015 and March 2016 in Germany concerned asylum seekers. Most infections were acquired abroad, but at least 24% accounted for autochthonous infections. Among asylum seekers, children aged five to nine years were overrepresented with 97 of 278 (35%) notified cases. The analysed hepatitis A virus sequences were primarily subgenotype IB strains and clustered with previously isolated samples from the Middle East, Turkey, Pakistan and East Africa. Except one transmission from an asymptomatic child to a nursery nurse working in a mass accommodation, we are not aware of infection chains involving asylum seekers and German residents. We conclude that asylum-seeking children and adolescents are susceptible to hepatitis A virus infections, particularly children aged five to nine years. Measures to prevent secondary infections in asylum seekers such as extended hygiene measures and post-exposure prophylaxis seem advisable.

Concentration and detection of hepatitis A virus and its indicator from artificial seawater using zeolite

Hepatitis A virus (HAV) infection is the leading worldwide cause of acute viral hepatitis, and outbreaks caused by this virus often occur in fecal polluted waters. Rapid concentration and detection of viral contamination in water environments can prevent economic loss and can identify the source of contamination within a short time. However, conventional methods for virus concentration are often laborious, time consuming, and subject to clogging. Furthermore, most methods require a secondary concentration step to reduce the final volume of samples. We developed a method to concentrate HAV from seawater using zeolite in aid of rapid detection. In this method,artificial seawater was inoculated with HAV (7-8 log TCID50) and filtered with zeolite. The viruses were then eluted from zeolite with sodium dodecyl sulfate and detected via real-time PCR (qPCR). Zeolite was able to concentrate HAV from artificial seawater with ∼99% efficiency in less than 5min and was more efficient in seawater than in fresh water. The entire concentration and detection can be done in approximately 2h. Compared to existing methods, this method eliminated the need for a secondary concentration step as well as the necessity to modify the pH or salinity of the seawater during concentration, and was simple and inexpensive.

Epidemiologic evaluation of multiple alternate microbial water quality monitoring indicators at three California beaches

INTRODUCTION

Advances in molecular methods provide new opportunities for directly measuring pathogens or host-associated markers of fecal pollution instead of relying on fecal indicator bacteria (FIB) alone for beach water quality monitoring. Adoption of new indicators depends on identifying relationships between either the presence or concentration of the indicators and illness among swimmers. Here we present results from three epidemiologic studies in which a broad range of bacterial and viral indicators of fecal contamination were measured simultaneously by either culture or molecular methods along with Enterococcus to assess whether they provide better health risk prediction than current microbial indicators of recreational water quality.

METHODS

We conducted prospective cohort studies at three California beaches -- Avalon Bay (Avalon), Doheny State Beach (Doheny), Surfrider State Beach (Malibu) -- during the summers of 2007, 2008 and 2009. The studies enrolled 10,785 swimmers across the beaches and recorded each swimmer's water exposure. Water and sand samples were collected several times per day at multiple locations at each beach and analyzed for up to 41 target indicators using 67 different methodologies. Interviewers contacted participants by phone 10-14 days later and recorded symptoms of gastrointestinal illness occurring after their beach visit. Regression models were used to evaluate the association between water quality indicators and gastrointestinal illness among swimmers at each beach.

RESULTS

F+ coliphage (measured using EPA Method 1602) exhibited a stronger association with GI illness than did EPA Method 1600 at the two beaches where it was measured, while a molecular method, F+ RNA Coliphage Genotype II, was the only indicator significantly associated with GI illness at Malibu. MRSA, a known pathogen, had the strongest association with GI illness of any microbe measured at Avalon. There were two methods targeting human-associated fecal anaerobic bacteria that were more strongly associated with GI illness than EPA Method 1600, but only at Avalon. No indicator combinations consistently had a higher odds ratio than EPA Method 1600, but one composite indicator, based on the number of pathogens detected at a beach, was significantly associated with gastrointestinal illness at both Avalon and Doheny when freshwater flow was high.

DISCUSSION

While EPA Method1600 performed adequately at two beaches based on its consistency of association with gastrointestinal illness and the precision of its estimated associations, F+ coliphage measured by EPA Method 1602 had a stronger association with GI illness under high risk conditions at the two beaches where it was measured. One indicator, F+ Coliphage Genotype II was the only indicator significantly associated with GI illness at Malibu. Several indicators, particularly those targeting human associated bacteria, exhibited relationships with GI illness that were equal to or greater than that of EPA Method 1600 at Avalon, which has a focused human fecal source. Our results suggest that site-specific conditions at each beach determine which indicator or indicators best predict GI illness.

Evolutionary origins of hepatitis A virus in small mammals

Hepatitis A virus (HAV) is an ancient and ubiquitous human pathogen recovered previously only from primates. The sole species of the genus Hepatovirus, existing in both enveloped and nonenveloped forms, and with a capsid structure intermediate between that of insect viruses and mammalian picornaviruses, HAV is enigmatic in its origins. We conducted a targeted search for hepatoviruses in 15,987 specimens collected from 209 small mammal species globally and discovered highly diversified viruses in bats, rodents, hedgehogs, and shrews, which by pairwise sequence distance comprise 13 novel Hepatovirus species. Near-complete genomes from nine of these species show conservation of unique hepatovirus features, including predicted internal ribosome entry site structure, a truncated VP4 capsid protein lacking N-terminal myristoylation, a carboxyl-terminal pX extension of VP1, VP2 late domains involved in membrane envelopment, and a cis-acting replication element within the 3D(pol) sequence. Antibodies in some bat sera immunoprecipitated and neutralized human HAV, suggesting conservation of critical antigenic determinants. Limited phylogenetic cosegregation among hepatoviruses and their hosts and recombination patterns are indicative of major hepatovirus host shifts in the past. Ancestral state reconstructions suggest a Hepatovirus origin in small insectivorous mammals and a rodent origin of human HAV. Patterns of infection in small mammals mimicked those of human HAV in hepatotropism, fecal shedding, acute nature, and extinction of the virus in a closed host population. The evolutionary conservation of hepatovirus structure and pathogenesis provide novel insight into the origins of HAV and highlight the utility of analyzing animal reservoirs for risk assessment of emerging viruses.

Foodborne hepatitis A outbreak associated with bakery products in northern Germany, 2012

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Hepatitis A Outbreak in Europe: Imported Frozen Berry Mix Suspected to be the Source of At least One Infection in Austria in 2013

We tested 19 sera from Austrian patients with acute hepatitis A. A serum from a 48-year-old female patient yielded HAV-nucleic acid that showed 99.7% homology to the HAV-sequence obtained from samples taken during the current outbreak in several European countries, which is associated with consumption of frozen berries. So far, Austria was considered not to be affected by this hepatitis A outbreak.

Coherence among different microbial source tracking markers in a small agricultural stream with or without livestock exclusion practices

Over 1,400 water samples were collected biweekly over 6 years from an intermittent stream protected and unprotected from pasturing cattle. The samples were monitored for host-specific Bacteroidales markers, Cryptosporidium species/genotypes, viruses and coliphages associated with humans or animals, and bacterial zoonotic pathogens. Ruminant Bacteroidales markers did not increase within the restricted cattle access reach of the stream, whereas the ruminant Bacteroidales marker increased significantly in the unrestricted cattle access reach. Human Bacteroidales markers significantly increased downstream of homes where septic issues were documented. Wildlife Bacteroidales markers were detected downstream of the cattle exclusion practice where stream and riparian habitat was protected, but detections decreased after the unrestricted pasture, where the stream and riparian zone was unprotected from livestock. Detection of a large number of human viruses was shown to increase downstream of homes, and similar trends were observed for the human Bacteroidales marker. There was considerable interplay among biomarkers with stream flow, season, and the cattle exclusion practices. There were no to very weak associations with Bacteroidales markers and bacterial, viral, and parasitic pathogens. Overall, discrete sample-by-sample coherence among the different microbial source tracking markers that expressed a similar microbial source was minimal, but spatial trends were physically meaningful in terms of land use (e.g., beneficial management practice) effects on sources of fecal pollution.

Comparative evaluation of a novel TaqMan real-time reverse transcription-polymerase chain reaction assay for hepatitis A virus detection

OBJECTIVE

To develop and evaluate a novel system for detecting and quantifying hepatitis A virus (HAV) nucleic acid.

METHODS

Real-time TaqMan® reverse transcription-polymerase chain reaction (PCR) procedures were established, based on amplification of the highly conserved 5'-non-coding region. Synthetic single-stranded RNA transcripts synthesized in vitro were used as the quantification standard. Ten-fold dilutions were prepared from HAV strain stock suspension to determine precision, accuracy, sensitivity and specificity. In addition, serum specimens from patients with acute HAV underwent clinical evaluation.

RESULTS

The novel assay had a detection limit for HAV RNA of 10 TCID50/ml (where TCID50 is median tissue culture infective dose). It was more sensitive and specific than the commercial quantitative PCR kit manufactured by Shanghai Zhijiang Bio-Tech. However, the Artus HAV RT-PCR kit (Qiagen) had the best performance of the three assays and had a detection limit of 5 TCID50/ml. The new HAV real-time PCR detection system was also successfully applied in 90 serum specimens from patients with confirmed acute HAV infection.

CONCLUSION

Considering its high reproducibility, sensitivity, specificity and simplicity, this novel amplification system may be suitable for wide clinical application as a diagnostic tool, and for the surveillance and investigation of infectious diseases in developing countries where HAV is endemic.

Comparison of different RT-qPCR assays for the detection of human and bovine group A rotaviruses and characterization by sequences analysis of genes encoding VP4 and VP7 capsid proteins

AIMS

The aim of this study was to compare the performance of four RT-qPCR assays for the detection of human and bovine group A rotaviruses and to characterize the positive samples by sequence analysis of VP4 and VP7 genes.

METHODS AND RESULTS

RNA extracted from eight human rotavirus strains, and a panel of 33 human and 25 bovine faecal samples was subjected to different RT-qPCR detection systems. Among these assays, only RT-qPCR primers and probe systems B and C were able to detect all human rotavirus strains from cell culture solutions and faecal samples. However, the results showed that the system C was generally more sensitive by one or two logs than the other RT-qPCR assays tested. With the bovine faecal samples, the most efficient RT-qPCR systems were B and A with the detection in 100 and 92% of samples tested, respectively. Human group A rotavirus G1P[8] and bovine G6P[11] were the most frequently used strains identified in this study. A G3P[9] strain, closely related to a feline rotavirus isolated in the USA, was also discovered in a human rotavirus infection.

CONCLUSION

The RT-qPCR system B was the only TaqMan assay evaluated in this study able to detect rotavirus RNA in all positive human and bovine faecal samples.

SIGNIFICANCE AND IMPACT OF THE STUDY

Utilization of only one RT-qPCR for the detection of human and bovine group A rotaviruses and the possibility of human infection by a feline rotavirus strain.

New approaches in microbial pathogen detection

Viruses are common causes of foodborne outbreaks. Viral diseases have low fatality rates but transmission to humans via food is important due to the high probability of consuming fecally contaminated food or water because of poor food handling. Because of the low infectious doses of some foodborne viruses, there is a need for standardization and the development of new sensitive methods for detecting viruses. The focus is on molecular and non-molecular approaches, and emerging methods for the detection of foodborne viruses. The detection of noroviruses, hepatitis A and E viruses, rotaviruses and adenoviruses will be discussed. The chapter will conclude with insights into future research directions.

Rapid detection method for hepatitis A virus from lettuce by a combination of filtration and integrated cell culture-real-time reverse transcription PCR

We have developed a rapid and simple method for filtration using a positively charged membrane to concentrate hepatitis A virus (HAV) from lettuce and an integrated cell culture-real-time reverse transcription PCR (ICC-real-time RT-PCR) to detect infectious HAV. The most suitable buffer for HAV concentration by filtration was 100 mM Tris-HCl, 50 mM glycine (pH 9.5). Filtration using the NanoCeram matrix was compared with polyethylene glycol precipitation for viral concentration from lettuce inoculated with 6 log RNA copies of HAV. The recovery rate of filtration was statistically higher than that of polyethylene glycol precipitation (47.3 versus 24.9%, respectively). The sensitivity of ICC-real-time RT-PCR for detection of infectious HAV was determined by inoculation of FRhK-4 cells with HAV (4 log to 0 log RNA copies). ICC-real-time RT-PCR detected infectious HAV on average 5 days earlier than cytopathic effects at all inoculation levels. HAV recovered from lettuce (approximately 3 log RNA copies) was also analyzed with ICC-real-time RT-PCR. Infectious HAV was detected within 2 days postinfection by ICC-real-time RT-PCR, whereas cytopathic effects were not observed until 7 days postinfection. Coupled with a virus concentration and purification system using a positively charged membrane, ICC-real-time RT-PCR has the potential to become a novel and rapid method for the detection of infectious HAV in vegetables.

The use of bovine serum albumin to improve the RT-qPCR detection of foodborne viruses rinsed from vegetable surfaces

AIMS

To demonstrate that produce rinsates used for RT-qPCR detection of foodborne viruses may cause significant PCR inhibition and propose a means to reduce its impact on sensitivity.

METHODS AND RESULTS

Here, it is shown that rinsing and concentration from spinach and precut lettuce have the potential to generate RNA extracts that are inhibitory to RT-qPCRs assembled from commercial kits for the detection of norovirus GII (NoV GII), hepatitis A virus (HAV), hepatitis E virus (HEV), rotavirus (RV) and feline calicivirus (FCV) as sample process control. It is further shown that the addition of bovine serum albumin (BSA) to those reactions restored a positive signal in all cases. The effect of BSA was dependent upon the primer/probe combination. Moreover, two of the detection systems (FCV and HAV) strongly benefited from the addition of BSA even in the absence of PCR inhibitors.

CONCLUSIONS

BSA was shown to restore positive signals in five different RT-qPCR systems that were otherwise completely inhibited by produce rinsate extracts. It is therefore suggested to consider the addition of BSA to RT-qPCRs for the detection of foodborne viruses when inhibition is observed.

SIGNIFICANCE AND IMPACT OF THE STUDY

This study clearly demonstrates the potency of PCR inhibitors generated during routine virus concentration from produce and that it can be alleviated by the addition of BSA to the RT-qPCRs. Although used elsewhere, the addition of BSA to PCRs is not a common practice in this growing field of research.

Prevalence of nucleic acid sequences specific for human parvoviruses, hepatitis A and hepatitis E viruses in coagulation factor concentrates

BACKGROUND AND OBJECTIVES

Due to their high resistance to inactivation procedures, nonenveloped viruses such as parvovirus B19, human bocavirus (HBoV), human parvovirus 4 (PARV4), hepatitis A (HAV) and hepatitis E virus (HEV) pose a particular threat to blood products. Virus transmission to patients treated with blood products presents an additional burden to disease. We determined the frequency and the amount of nucleic acid specific for nonenveloped viruses in recently manufactured preparations of commercial coagulation factor concentrates.

MATERIALS AND METHODS

At least three different batches of each of 13 different plasma-derived and recombinant coagulation factor products were tested for the presence and the amount of nucleic acid for parvovirus B19, HBoV, human parvovirus 4, hepatitis A virus and HEV by using quantitative polymerase chain reaction.

RESULTS

Whereas none of the recombinant products tested positive for any of these viruses, parvovirus B19 DNA with amounts ranging between 2×10(1) and 1.3×10(3) genome equivalents/ml was detected in five plasma-derived products. In addition to parvovirus B19 genotype 1, genotypes 2 and 3 were observed in two batches of a factor VIII/von-Willebrand factor product. In two products (one factor VIII concentrate and one activated prothrombin complex concentrate), a combination of both genotypes 1 and 2 of parvovirus B19 was detected.

CONCLUSION

The data show that nucleic acids from several relevant nonenveloped viruses are not found at detectable levels in coagulation factor concentrates. In some cases, parvovirus B19 DNA was detectable at low levels. Testing of the plasma pools for the full range of parvovirus genotypes is advocated for ensuring product safety.

Evaluation of rapid methods and novel indicators for assessing microbiological beach water quality

A broad suite of new measurement methods and indicators based on molecular measurement technology have been developed to assess beach water quality, but they have generally been subjected to limited testing outside of the laboratory in which they were developed. Here we evaluated 29 assays targeting a variety of bacterial, viral, and chemical analytes by providing the method developers with twelve blind samples consisting of samples spiked with known concentration of sewage or gull guano and negative controls. Each method was evaluated with respect to its ability to detect the target organism, absence of signal in the negative controls and repeatability among replicates. Only six of the 30 methods detected their targets in at least 75% of the samples while consistently determining the absence of the target in the negative controls. Among quantitative methods, QPCR for Bacteroides thetaiotamicron and Enterococcus detected by Luminex reliably identified all but one sample containing human fecal material and produced no false positive results. Among non-quantitative methods, the Enterococcus esp gene, the Bacteroidales human specific marker and culture-based coliphage were the most reliable for identifying human fecal material. We also found that investigator-specific variations of methods targeting the same organism often produced different results.

Development of a TaqMan real-time PCR assay for quantification of airborne conidia of Botrytis squamosa and management of botrytis leaf blight of onion

The use of a DNA-based method for quantifying airborne inoculum of Botrytis squamosa, a damaging pathogen of onion, was investigated. A method for purifying DNA from conidia collected using rotating-arm samplers and quantifying it using a TaqMan real-time quantitative polymerase chain reaction (qPCR) assay is described. The sensitivity of the qPCR assay was high, with a detection limit of 2 conidia/rod. A linear relationship between numbers of conidia counted with a compound microscope and those determined with the qPCR assay was obtained. Receiver operating characteristic curve analysis was used to evaluate the reliability of the two methods of conidia quantification (microscope examination and qPCR assay) to predict the risk of disease being below or above a damage threshold (D(th)). In total, 142 field samples from commercial onion fields were analyzed. At damage thresholds of 5 or 10 lesions/leaf, conidia quantification with the qPCR assay was more reliable at predicting disease risk than conidia quantification based on microscope counts. The proportion of decisions where the disease was present and predicted was higher for the qPCR assay than for the microscope counts, with values of 0.95 and 0.89 compared with 0.79 and 0.81 for D(th) of 5 and 10 lesions/leaf, respectively. The proportion of decisions where the disease was present but not predicted was lower for the qPCR assay than for microscope counts, with values of 0.05 and 0.11 compared with 0.20 and 0.19 for D(th) of 5 and 10 lesions/leaf, respectively. The results demonstrated that this new qPCR assay was reliable for quantifying B. squamosa airborne inoculum in commercial onion fields and that molecular conidia quantification could be used as a component of a risk management system for Botrytis leaf blight.

Nested real-time PCR for hepatitis A detection

AIMS

The hepatitis A virus (HAV) is one of the most important human foodborne pathogens causing a number of worldwide outbreaks each year. The detection of HAV in food samples remains a complex issue, because commonly used detection tools, such as conventional or even real-time PCR assays, are often unable to detect HAV with sufficient sensitivity. The aims of this study were to develop highly sensitive and specific nested real-time PCR (NRT-PCR)-based method for HAV detection in food and to compare it with currently available methods.

METHODS AND RESULTS

By combining conventional PCR, nested PCR and real-time PCR techniques, we have developed a specific NRT-PCR assay for the detection of HAV. The procedure involves two consecutive PCRs, the first of which is performed as a conventional RT-PCR using primers specific for HAV 5' noncoding region. The second reaction involves a real-time PCR using a nested primer pair specific for the first PCR product and a TaqMan probe.

CONCLUSIONS

We have developed a novel NRT-PCR method capable of detecting as little as 0.2 PFU of HAV, which is significantly more sensitive than any other PCR technique tested in our system.

SIGNIFICANCE AND IMPACT OF THE STUDY

NRT-PCR provides a potentially useful method for detecting HAV at extremely low levels, as frequently found in food samples, and can be potentially adopted as a regulatory method to ensure food safety.

The feline calicivirus as a sample process control for the detection of food and waterborne RNA viruses

Many food and waterborne outbreaks of infectious disease are caused by viruses. While numerous methods exist and are being developed to test food and water for the presence of enteric viruses, there is no standard control for the comparison of different methods. Potential control viruses should be well characterized, share the physical characteristics of the enterically infecting viruses and not normally be associated with foods. Here, the feline calicivirus (FCV) is proposed as a sample process control for methods aimed at the extraction and detection of RNA viruses in food and water. FCV is shown to be useful as a control for the extraction of hepatitis A virus (HAV) from water using filtration technology and from strawberries using the Pathatrix system. The FCV standard provides a valuable quality control tool when testing potentially contaminated food samples.

Solid-phase capture of pathogenic bacteria by using gangliosides and detection with real-time PCR

We developed a method for concentrating pathogens from samples without enrichment. Immobilized gangliosides concentrated bacteria for detection with real-time PCR. A sensitivity of approximately 4 CFU/ml (3 h) in samples without competing microflora was achieved. Samples with competing microflora had a sensitivity of 40,000 CFU/ml. The variance was less than one cycle.