Outbreaks of viral gastroenteritis: whatʼs new in 2004?

Validation of a Laboratory-Developed Triplex Molecular Assay for Simultaneous Detection of Gastrointestinal Adenovirus and Rotavirus in Stool Specimens

Enteric viral pathogens causing gastroenteritis include adenovirus and rotavirus, among others. Rotavirus is the leading cause of severe diarrhea in infants and young children worldwide. Among the adenoviruses known to cause gastroenteritis are those of species F (serotypes 40, 41). Here, we describe the development and validation of a laboratory-developed gastrointestinal triplex rRT-PCR (triplex) assay that targets adenovirus and rotavirus. Stool specimens were tested from patients across Ontario. Specimens were previously tested for adenovirus and/or rotavirus by electron microscopy (EM) or immunochromatographic test (ICT). Triplex sensitivity, specificity, positive and negative predictive values compared to Seegene assay (a commercial assay used here as the standard reference method) were 100%, 97.8%, 86.0%, 100% for adenovirus, and 99.1%, 98.4%, 96.3%. 99.6% for rotavirus, respectively. The triplex assay had a 95.2% and 97.3% overall percent agreements (OPAs) when compared to EM for adenovirus or rotavirus detection, respectively, and an OPA of 90.9% when compared to rotavirus ICT for rotavirus detection. Triplex assay exhibited similar performance to the Seegene assay for both adenovirus and rotavirus and detected more adenovirus and rotavirus than traditional testing methods. The high performance along with lower cost and reduced turnaround time makes the triplex assay a desirable testing method for a clinical microbiology laboratory.

Development of a multiplex real-time PCR assay for detection of human enteric viruses other than norovirus using samples collected from gastroenteritis patients in Fukui Prefecture, Japan

There are many varieties of gastroenteritis viruses, of which norovirus (NoV) accounts for over 90% of the viral food poisoning incidents in Japan. However, protocols for rapidly identifying other gastroenteritis viruses need to be established to investigate NoV-negative cases intensively. In this study, a multiplex real-time PCR assay targeting rotavirus A, rotavirus C, sapovirus, astrovirus, adenovirus, and enterovirus was developed using stool samples collected from gastroenteritis patients between 2010 and 2013 in Fukui Prefecture, Japan. Of the 126 samples collected sporadically from pediatric patients with suspected infectious gastroenteritis, 51 were positive for non-NoV target viruses, whereas 27 were positive for NoV, showing a high prevalence of non-NoV viruses in pediatric patients. In contrast, testing in 382 samples of 58 gastroenteritis outbreaks showed that non-NoV viruses were detected in 13 samples, with NoV in 267. Of the 267 NoV-positive patients, only two were co-infected with non-NoV target viruses, suggesting that testing for non-NoV gastroenteritis viruses in NoV-positive samples was mostly unnecessary in outbreak investigations. Given these results, multiplex real-time PCR testing for non-NoV gastroenteritis viruses, conducted separately from NoV testing, may be helpful to deal with two types of epidemiological investigations, regular surveillance of infectious gastroenteritis and urgent testing when gastroenteritis outbreaks occur.

Evaluation and verification of the Seeplex Diarrhea-V ACE assay for simultaneous detection of adenovirus, rotavirus, and norovirus genogroups I and II in clinical stool specimens

Acute viral gastroenteritis is an intestinal infection that can be caused by several different viruses. Here we describe the evaluation and verification of Seeplex Diarrhea-V ACE (Seeplex DV), a novel commercial multiplex reverse transcription-PCR (RT-PCR) assay that detects 5 diarrheal pathogens, including adenovirus, rotavirus, norovirus genogroup I (GI) and GII, and astrovirus. We describe a retrospective study of 200 clinical specimens of which 177 were stool specimens previously tested for the presence of gastrointestinal viruses by electron microscopy (EM) and/or real-time RT-PCR (rRT-PCR). The remaining 23 specimens comprised other human pathogens of viral or bacterial origin. Discordant norovirus GI and GII results were resolved using a commercial kit; discordant adenovirus and rotavirus results were resolved using a home brew multiplex rRT-PCR assay. Diagnostic sensitivities and specificities were calculated before and after discordant analysis. After discordant analysis, estimated diagnostic sensitivities were 100% for adenovirus, rotavirus, and norovirus GI and 97% for norovirus GII. Diagnostic specificities after discordant analysis were 100% for adenovirus, rotavirus, and norovirus GI and 99.4% for norovirus GII. The 95% limits of detection were 31, 10, 2, and 1 genome equivalent per reaction for adenovirus, rotavirus, and norovirus GI and GII, respectively. The results demonstrate that the Seeplex DV assay is sensitive, specific, convenient, and reliable for the simultaneous detection of several viral pathogens directly in specimens from patients with gastroenteritis. Importantly, this novel multiplex PCR assay enabled the identification of viral coinfections in 12 (6.8%) stool specimens.

Norovirus GII-4 2006b variant circulating in patients with acute gastroenteritis in Thailand during a 2006-2007 study

Noroviruses (NoVs) are recognized as a significant cause of acute gastroenteritis in children and adults. A 14-month study, from January 2006 to February 2007, was undertaken in a hospital in Thailand to determine the prevalence and genetic characterization of NoVs in patients of all ages with acute gastroenteritis. Based on reverse transcription-nested polymerase chain reaction (RT-nested PCR), NoVs were detected in 122 of 273 (44.7%) collected stool samples. Of the 122 NoV-positive samples, 28 (23%) belonged to GI, 79 (64.8%) belonged to GII, and 15 (12.2%) were mixed infections of GI and GII strains. Three NoV GI-positive and 42 NoV GII-positive samples were characterized successfully by DNA sequencing of the RT-nested PCR products and phylogenetic analysis. For NoV GI, two genotypes were identified: GI-2 (one sample) and GI-6 (two samples). NoV GII could be classified further into five distinct genotypes: GII-2 (1 sample), GII-3 (3 samples), GII-4 (14 samples), GII-6 (3 samples), and GII-17 (2 samples), and one unclassified genotype (19 samples). All NoV GII-4 strains showed 88-98% nucleotide identity with NoV GII-4 2006b variants reported worldwide. Among genotypes of NoV characterized, one co-infected stool sample exhibited NoVs GI-6 and GII-4 2006b. This study suggests that there is an important role of NoVs as etiologic agents in patients with acute gastroenteritis. The predominant circulating genotype of NoV infections is GII-4 2006b variant.

Antiviral strategies to control calicivirus infections

Caliciviridae are human or non-human pathogenic viruses with a high diversity. Some members of the Caliciviridae, i.e. human pathogenic norovirus or rabbit hemorrhagic disease virus (RHDV), are worldwide emerging pathogens. The norovirus is the major cause of viral gastroenteritis worldwide, accounting for about 85% of the outbreaks in Europe between 1995 and 2000. In the United States, 25 million cases of infection are reported each year. Since its emergence in 1984 as an agent of fatal hemorrhagic diseases in rabbits, RHDV has killed millions of rabbits and has been dispersed to all of the inhabitable continents.

In view of their successful and apparently increasing emergence, the development of antiviral strategies to control infections due to these viral pathogens has now become an important issue in medicine and veterinary medicine. Antiviral strategies have to be based on an understanding of the epidemiology, transmission, clinical symptoms, viral replication and immunity to infection resulting from infection by these viruses. Here, we provide an overview of the mechanisms underlying calicivirus infection, focusing on the molecular aspects of replication in the host cell. Recent experimental data generated through an international collaboration on structural biology, virology and drug design within the European consortium VIZIER is also presented. Based on this analysis, we propose antiviral strategies that may significantly impact on the epidemiological characteristics of these highly successful viral pathogens.

Novel approach for detection of enteric viruses to enable syndrome surveillance of acute viral gastroenteritis

Acute gastroenteritis is one of the most common diseases worldwide, with viruses, particularly noroviruses, being the leading cause in developed countries. In The Netherlands, systematic surveillance of gastroenteritis outbreaks of suspected viral etiology was established by the National Institute for Public Health and the Environment in 1994. Since 2002, the total number of outbreaks reported has been increasing, and with that comes the need for sensitive assays that can be performed quickly. In addition, the diagnostic demand changed so that now the proportion of samples from hospitals is higher and there is a need for patient-based test results. In order to target the diagnosis of acute gastroenteritis, we reviewed our data on outbreaks of gastroenteritis and the prevalence of individual viruses to provide a priority list of viruses for which samples should be evaluated. Random primers were used to replace the separate specific primers for each virus used in the reverse transcription steps. The individual PCR assays were replaced by multiplex PCR assays. We employed a two-step method in which in the first step we screened for the most common causes of viral gastroenteritis, noroviruses of genogroup II and rotaviruses of group A, with equine arteritis virus used as the internal control. Subsequently, in the second step, two parallel PCR assays were developed for the detection of noroviruses of genogroup I and equine arteritis virus in one run and adenoviruses, sapoviruses, and astroviruses in the other run. The specificities of the assays were calculated to be 92.5% for the assay for noroviruses of genogroup I and 100% for the assays for all other viruses, the detection limits were equal for all viruses, and the turnaround time was reduced to 1 day compared to the at least 3 days required for the methods used previously. This approach allows the targeted, rapid, and cost-effective elucidation of the causes of acute gastroenteritis outbreaks.

Molecular characterization of rotaviruses, noroviruses, sapovirus, and adenoviruses in patients with acute gastroenteritis in Thailand

Outbreaks of viral gastroenteritis occur worldwide including Thailand. Unfortunately, there is limited information since etiologic agents have not been identified in several outbreaks of nonbacterial gastroenteritis. The genotype of enteric viruses causing acute gastroenteritis in Thailand was determined using reverse transcription-multiplex polymerase chain reaction and DNA sequencing. From January 2006 to February 2007, stool samples were collected from patients with acute gastroenteritis of all age groups attending a hospital in Thailand, and patients with nonbacterial acute gastroenteritis (262 patients) were tested for enteric viruses. The overall positive detection rate of enteric viruses was 14.9%; group A rotaviruses (6.1%), noroviruses (6.5%): GI (0.8%) and GII (5.7%), adenoviruses (1.5%), and sapoviruses (0.8%) were found. Group B and C rotaviruses, and astroviruses were not detected in the enrolled patients. Viral acute gastroenteritis occurred in children less than 15 years of age (25.2%, 33/131) with higher frequency than in adults (4.6%, 6/131), P-value <0.001. Rotavirus G1 was the most predominant genotype, followed by G3, and G9. Among noroviruses, GI-2 was identified; whereas, GII was predominant with a high frequency of GII-4 observed, followed by GII-16, GII-2, GII-3, and GII-12. Sapovirus GII-3 and human adenoviruses were identified. This study suggests that enteric viruses play an essential role in patients with acute gastroenteritis attending hospital and mainly in children who have a higher prevalence of group A rotaviruses and noroviruses. The genetic analyses provide molecular epidemiological data for viruses important to public health.

Aetiology and epidemiology of viral gastroenteritis outbreaks in Catalonia (Spain) in 2004-2005

BACKGROUND

Acute infectious gastroenteritis causes substantial morbidity and economic loss.

OBJECTIVE

The aetiology, epidemiology, and clinical features of acute viral gastroenteritis outbreaks reported during 1 year in Catalonia were investigated.

STUDY DESIGN

This was a population-based study in which enzyme immunoassay and reverse transcriptase-polymerase chain reaction (RT-PCR) techniques were used to determine the presence of virus in stool specimens from outbreaks clinically and epidemiologically compatible with a viral aetiology and negative for bacteria, parasites and toxins.

RESULTS

Sixty outbreaks affecting 1791 people were evaluated. Fifty-five outbreaks were positive for norovirus, four were positive for norovirus and other microorganisms (adenovirus, astrovirus, S. Typhimurium and V. parahaemolyticus in one each). Thirty-seven percentage of the outbreaks occurred in collective catering; 18.3% in nursing homes; 10% in hospitals and long-term-care facilities. Foodborne transmission accounted for 50% of outbreaks. Norovirus genotype GGII.4 accounted for 42% of all the outbreaks, being more prevalent in nursing homes, hospital and long-term-care facilities.

CONCLUSIONS

The large number of norovirus outbreaks and resulting health service demand and absenteeism indicate that acute gastroenteritis caused by norovirus is an important health problem in Catalonia. Preventive measures should target education and control of food handlers, and immediate specific control measures should be adopted in institutions.

Simple and rapid F+ coliphage culture, latex agglutination, and typing assay to detect and source track fecal contamination

Simple, rapid, and reliable fecal indicator tests are needed to better monitor and manage ambient waters and treated waters and wastes. Antibody-coated polymeric bead agglutination assays can fulfill these needs and are inexpensive and portable for nonlaboratory settings, and their reagents can be stored at ambient temperatures for months. The goal of this study was to develop, optimize, and validate a rapid microbial water quality monitoring assay using F+ coliphage culture, latex agglutination, and typing (CLAT) to detect F+ coliphage groups with antibody-coated particles. Rapid (180 min) F+ coliphage culture gave comparable results to those with the 16- to 24-h culture time used in EPA method 1601 and was amenable to CLAT assay detection. CLAT was performed on a cardboard card by mixing a drop of coliphage enrichment culture with a drop of antibody-coated polymeric beads as the detection reagent. Visual agglutination or clumping of positive samples occurred in <60 seconds. The CLAT assay had sensitivities of 96.4% (185/192 samples) and 98.2% (161/164 samples) and specificities of 100% (34/34 samples) and 97.7% (129/132 samples) for F+ RNA and DNA coliphages, respectively. CLAT successfully classified F+ RNA coliphages into serogroups typically obtained from human (groups II and III) and animal (groups I and IV) fecal sources, in similar proportions to those obtained with a nucleic acid hybridization assay. This novel group-specific antibody-based particle agglutination technique for rapid and simple detection and grouping of F+ coliphages provides a new and improved tool for monitoring the microbiological quality of drinking, recreational, shellfishing, and other waters.

Etiological role of viruses in outbreaks of acute gastroenteritis in The Netherlands from 1994 through 2005

Acute gastroenteritis is one of the most common diseases worldwide. In developed countries, viruses, particularly noroviruses, are recognized as the leading cause. In The Netherlands, the surveillance of gastroenteritis outbreaks with suspected viral etiologies (as determined by Kaplan criteria) was established by the National Institute for Public Health and the Environment in 1994. This paper presents an overview of viral gastroenteritis outbreaks reported from 1994 through 2005. A minimum epidemiological data set consisting of the associated setting(s), the probable transmission mode, the date of the first illness and the date of sampling, the number of persons affected, and the number of hospitalizations was requested for each reported outbreak. Stool samples were tested for the presence of norovirus, sapovirus, rotavirus, astrovirus, adenovirus, and Aichi virus by electron microscopy, enzyme-linked immunosorbent assay, and/or reverse transcription-PCR. A total of 6,707 stool samples from 941 gastroenteritis outbreaks were investigated. Noroviruses were detected as the causative agent in 735 (78.1%) of the outbreaks, and rotaviruses, adenoviruses, and astroviruses were found to be responsible for 46 (4.9%), 9 (1.0%), and 5 (0.5%) outbreaks, respectively. Among the gastroenteritis outbreaks in which a mode of transmission was identified, most outbreaks (38.1%) were associated with person-to-person transmission, and the majority (54.9%) of the outbreaks investigated were reported by residential institutions. Since 2002, the total number of outbreaks reported and the number of unexplained outbreaks have increased. Furthermore, the number of rotavirus-associated outbreaks has increased, especially in nursing homes. Despite thorough testing, 115 (12.2%) outbreaks suspected of having viral etiologies remain unexplained. Increases in numbers of reported outbreaks may indicate undefined changes in the criteria for reporting or the emergence of new pathogens.

Detection of Norovirus genogroup I and II by multiplex real-time RT- PCR using a 3'-minor groove binder-DNA probe

BACKGROUND

Due to an increasing number of norovirus infections in the last years rapid, specific, and sensitive diagnostic tools are needed. Reverse transcriptase-polymerase chain reactions (RT-PCR) have become the methods of choice. To minimize the working time and the risk of carryover contamination during the multi-step procedure of PCR the multiplex real-time RT-PCR for the simultaneous detection of genogroup I (GI) and II (GII) offers advantages for the handling of large amounts of clinical specimens.

METHODS

We have developed and evaluated a multiplex one-tube RT-PCR using a combination of optimized GI and GII specific primers located in the junction between ORF1 and ORF2 of the norovirus genome. For the detection of GI samples, a 3'-minor groove binder-DNA probe (GI-MGB-probe) were designed and used for the multiplex real-time PCR.

RESULTS

Comparable results to those of our in-house nested PCR and monoplex real-time-PCR were only obtained using the GI specific MGB-probe. The MGB-probe forms extremely stable duplexes with single-stranded DNA targets, which enabled us to design a shorter probe (length 15 nucleotides) hybridizing to a more conserved part of the GI sequences. 97% of 100 previously norovirus positive specimens (tested by nested PCR and/or monoplex real-time PCR) were detected by the multiplex real-time PCR. A broad dynamic range from 2 x 10(1) to 2 x 10(7) genomic equivalents per assay using plasmid DNA standards for GI and GII were obtained and viral loads between 2.5 x 10(2) and 2 x 10(12) copies per ml stool suspension were detected.

CONCLUSION

The one-tube multiplex RT real-time PCR using a minor groove binder-DNA probe for GI is a fast, specific, sensitive and cost-effective tool for the detection of norovirus infections in both mass outbreaks and sporadic cases and may have also applications in food and environmental testing.

Nosocomial rotavirus infection in European countries: a review of the epidemiology, severity and economic burden of hospital-acquired rotavirus disease

The data currently available on the epidemiology, severity and economic burden of nosocomial rotavirus (RV) infections in children younger than 5 years of age in the major European countries are reviewed. In most studies, RV was found to be the major etiologic agent of pediatric nosocomial diarrhea (31-87%), although the number of diarrhea cases associated with other virus infections (eg, noroviruses, astroviruses, adenoviruses) is increasing quickly and almost equals that caused by RVs. Nosocomial RV (NRV) infections are mainly associated with infants 0-5 months of age, whereas community-acquired RV disease is more prevalent in children 6-23 months of age. NRV infections are seasonal in most countries, occurring in winter; this coincides with the winter seasonal peak of other childhood virus infections (eg, respiratory syncytial virus and influenza viruses), thus placing a heavy burden on health infrastructures. A significant proportion (20-40%) of infections are asymptomatic, which contributes to the spread of the virus and might reduce the efficiency of prevention measures given as they are implemented too late. The absence of effective surveillance and of reporting of NRV infections in any of the 6 countries studied (France, Germany, Italy, Poland, Spain and the United Kingdom) results in severe underreporting of NRV cases in hospital databases and therefore in limited awareness of the importance of NRV disease at country level. The burden reported in the medical literature is potentially significant and includes temporary reduction in the quality of children's lives, increased costs associated with the additional consumption of medical resources (increased length of hospital stay) and constraints on parents'/hospital staff's professional lives. The limited robustness and comparability of studies, together with an evolving baseline caused by national changes in health care systems, do not presently allow a complete and accurate overview of NRV disease at country level to be obtained. RV is highly contagious, and the efficiency of existing prevention measures (such as handwashing, isolation and cohorting) is variable, but low at the global level because of the existence of numerous barriers to implementation (eg, lack of staff, high staff turnover, inadequate hospital infrastructure). Prevention of RV infection by mass vaccination could have a positive impact on the incidence of NRV by reducing the number of children hospitalized for gastroenteritis, therefore reducing the number of hospital cross-infections and associated costs.