Persistence of Hepatitis A Virus RNA in Water, on Non-porous Surfaces, and on Blueberries

Comparison of sample pretreatments used to distinguish between infectious and non-infectious foodborne viruses by RT-qPCR

To detect viruses such as hepatitis A virus (HAV) and human norovirus (HuNoV) in foods, RT-qPCR or other molecular methods are used, which cannot distinguish between infectious and non-infectious virions. Samples can be pretreated to limit detection to intact and presumably infectious virions. We compared propidium monoazide (PMA or PMAxx), platinum (IV) chloride (PtCl4), magnetic silica beads and centrifugal filter using HAV or HuNoV inactivated by heat, pulsed light, or sodium hypochlorite (NaOCl). PMAxx completely or nearly eliminated (3.96 ± 1.24 log gc) the RT-qPCR signal of HAV inactivated at 100°C for 10 min. Pretreatments could not reduce significantly RT-qPCR signal of HAV after pulsed light (0.74 ± 0.36 log gc) and NaOCl (0.24 ± 0.14 log gc) inactivation. Enzymatic treatments did not improve the results obtained with PMAxx. The exudate of raspberry, strawberry or oyster used as food matrices needed dilution by at least tenfold for PMAxx to to yield results comparable to virions without a food matrix. Overall, PMAxx shows good potential to discriminate between infectious and non-infectious despite some remaining limitations.

How long do bacteria, fungi, protozoa, and viruses retain their replication capacity on inanimate surfaces? A systematic review examining environmental resilience versus healthcare-associated infection risk by "fomite-borne risk assessment"

SUMMARYIn healthcare settings, contaminated surfaces play an important role in the transmission of nosocomial pathogens potentially resulting in healthcare-associated infections (HAI). Pathogens can be transmitted directly from frequent hand-touch surfaces close to patients or indirectly by staff and visitors. HAI risk depends on exposure, extent of contamination, infectious dose (ID), virulence, hygiene practices, and patient vulnerability. This review attempts to close a gap in previous reviews on persistence/tenacity by only including articles (n = 171) providing quantitative data on re-cultivable pathogens from fomites for a better translation into clinical settings. We have therefore introduced the new term "replication capacity" (RC). The RC is affected by the degree of contamination, surface material, temperature, relative humidity, protein load, organic soil, UV-light (sunlight) exposure, and pH value. In general, investigations into surface RC are mainly performed in vitro using reference strains with high inocula. In vitro data from studies on 14 Gram-positive, 26 Gram-negative bacteria, 18 fungi, 4 protozoa, and 37 viruses. It should be regarded as a worst-case scenario indicating the upper bounds of risks when using such data for clinical decision-making. Information on RC after surface contamination could be seen as an opportunity to choose the most appropriate infection prevention and control (IPC) strategies. To help with decision-making, pathogens characterized by an increased nosocomial risk for transmission from inanimate surfaces ("fomite-borne") are presented and discussed in this systematic review. Thus, the review offers a theoretical basis to support local risk assessments and IPC recommendations.

A Cell-Based Electrochemical Biosensor for the Detection of Infectious Hepatitis A Virus

Hepatitis A virus (HAV), a major cause of acute liver infections, is transmitted through the fecal-oral route and close contact with infected individuals. Current HAV standardized methods rely on the detection of virus antigen or RNA, which do not differentiate between infectious and non-infectious HAV. The objective of this study was to develop a prototype cell-based electrochemical biosensor for detection of infectious HAV. A cell culture-adapted HAV strain (HM175/18f) and its permissive cells (FRhK-4), along with gold nanoparticle-modified screen-printed electrodes, were used to develop the biosensor. Electrochemical impedance spectroscopy was used to quantify the electrical impedance signal. Nyquist plots showed successful fabrication of the cell-based biosensor. The optimum period of HAV incubation with the biosensor was 6 h. A significant linear relationship (R2 = 0.98) was found between the signal and a 6-log range of HAV titers, with a limit of detection of ~5 TCID50/mL (tissue culture infectious dose). The biosensor did not detect non-target viruses such as feline calicivirus and human coronavirus 229E. The biosensor was stable for 3 to 7 days at an abusive temperature (37 °C), retaining ~90 to 60% of the original signal, respectively. In conclusion, this prototype cell-based biosensor is capable of rapidly detecting low levels of infectious HAV.

A Useful Method to Provide Infectious and Cultivable In Vitro Naked Viral Particles of Hepatitis A Virus

Hepatitis A virus (HAV) is an enteric virus mainly transmitted by the faecal-oral route. Belonging to the Picornaviridae family, HAV was first described as small naked particles, like all viruses of this family. However, for about a decade, it was demonstrated that HAV particles can exist surrounded by a lipid bilayer. This type of particle, called enveloped HAV (eHAV), acquires its lipid bilayer by hijacking a part of cell membranes during the virion egress in the last steps of the viral cycle. In vitro culture systems produce mainly eHAV, and so, to date, most of the studies on HAV have been carried out using this type of viral particle. In this study, a method based on lipid bilayer removal by chemical delipidation is proposed for the production of naked HAV particles. The resulting naked HAV particles conserve their infectivity and are therefore fully cultivable in vitro. By using this method, naked HAV particles can easily be produced in vitro and can be useful to perform further studies such as inactivation processes for the food industry, as HAV is a main concern for food safety.

Evaluation of a new automated viral RNA extraction platform for hepatitis A virus and human norovirus in testing of berries, lettuce, and oysters

Fruits, vegetables, and shellfish are often associated with outbreaks of illness caused particularly by human norovirus (HuNoV) and hepatitis A virus (HAV), the leading causative agents of foodborne illness worldwide. The aim of this study was to evaluate a new automated nucleic acid extraction platform (EGENE-UP EASYPREP) for enteric viruses in several at-risk food matrices and to test its limit of detection in comparison to a semi-automated method (EGENE-UP) using Boom methodology for nucleic acid extraction as suggested in the reference method ISO 15216-2:2019. Fresh and frozen raspberries, frozen blackberries, romaine lettuce and oyster digestive glands were artificially contaminated with HAV, HuNoV GII.4 or HuNoV GI.7 at 102, 103 or 104 genome copies/sample. Virus was then recovered from the food matrix using the ISO method. Viral RNA extracted from frozen berry samples by the automated system was purified on a column for additional removal of RT-qPCR inhibitors. For fresh raspberry, oysters, and romaine lettuce, the two extraction platforms were deemed equivalent. For frozen raspberry, the automated platform appeared to be more efficient for viral recovery, particularly for HAV and HuNoV GI at lower concentrations. With frozen blackberries, the two platforms may be considered equivalent for all targeted viruses. However, the automated method led to less sample-associated inhibition of the PCR, 56.5 % of samples versus 95.0 % for the semi-automated. We thus found that the automated extraction can be performed easily by users while obtaining equivalent or even superior results to the ISO 15216-2:2019 method, and therefore appears to be suitable for routine sanitary monitoring in food processing and for tracing outbreaks of illness.

Concentration of foodborne viruses eluted from fresh and frozen produce: Applicability of ultrafiltration

Foodborne illnesses involving raw and minimally processed foods are often caused by human noroviruses (HuNoV) and hepatitis A virus (HAV). Since food is contaminated usually with small numbers of virions, these must be eluted from the food surface and then concentrated for detection. The objective of this study was to optimize an ultrafiltration (UF) concentration method for HAV and HuNoVs present on various fresh and frozen produce. The detection range of the optimized method and its applicability to different food matrices was compared to the reference method ISO 15216-1:2017. Strawberry, raspberry, blackberry, lettuce, and green onion (25 g) were contaminated with HAV, HuNoV GI.7 and HuNoV GII.4 and then recovered therefrom by elution. A commercial benchtop UF device was used for the concentration step. Viral RNA was extracted and detected by RT-qPCR. From fresh strawberries, recovery of HAV loaded at 104 genome copies per sample was 30 ± 13 %, elution time had no significant impact, and UF membrane with an 80-100 kDa cut-off in combination with Tris-glycine elution buffer at pH 9.5 was found optimal. At lower copy numbers on fresh strawberry, at least 1 log lower numbers of HuNoV were detectable by the UF method (103 vs 104 GII.4 copies/sample and 101 vs 103 GI.7 copies/sample), while HAV was detected at 101 genome copies/sample by both methods. Except on raspberry, the UF method was usually equivalent to the ISO method regardless of the virus tested. The UF method makes rapid viral concentration possible, while supporting the filtration of large volume of sample. With fewer steps and shorter analysis time than the ISO method, this method could be suitable for routine analysis of viruses throughout the food production and surveillance chain.

Impact of Capsid and Genomic Integrity Tests on Norovirus Extraction Recovery Rates

Human norovirus (HuNoV) is the leading pathogen responsible for food-borne illnesses. However, both infectious and non-infectious HuNoV can be detected by RT-qPCR. This study evaluated the efficiency of different capsid integrity treatments coupled with RT-qPCR or a long-range viral RNA (long RT-qPCR) detection to reduce the recovery rates of heat inactivated noroviruses and fragmented RNA. The three capsid treatments evaluated (RNase, the intercalating agent PMAxx and PtCl₄) reduced the recovery of heat inactivated HuNoV and murine norovirus (MNV) spiked on lettuce, when combined with the ISO 15216-1:2017 extraction protocols. However, PtCl₄ also reduced non-heat-treated noroviruses recovery as estimated by RT-qPCR. The PMAxx and RNase treatments had a similar effect on MNV only. The most efficient approaches, the RNase and PMAxx treatments, reduced the heat-inactivated HuNoV recovery rates estimated using RT-qPCR by 2 and >3 log, respectively. The long RT-qPCR detection approach also reduced the recovery rates of heat inactivated HuNoV and MNV by 1.0 and 0.5 log, respectively. Since the long-range viral RNA amplification could be applied to verify or confirm RT-qPCR results, it also provides some advantages by reducing the risk of false positive HuNoV results.

Prevalence of Foodborne Viruses in Berries Harvested in Canada

It is known that the transmission of different foodborne viruses can occur either via discharge of contaminated water close to the production environment or via close contact with animal feces. Cranberries are intimately associated with water throughout their production cycle, and blueberries grow close to the ground which could lead to contact with wildlife. The aim of this study was to evaluate the prevalence of human norovirus (HuNoV GI and GII), hepatitis A virus (HAV) and hepatitis E virus (HEV) in two berries produced commercially in Canada. The detection of HuNoV and HAV on RTE cranberries and of HEV on wild blueberries was evaluated using the ISO method 15216-1:2017. Only 3 of 234 cranberry samples tested positive for HuNoV GI (3.6, 7.4, 5.3 genome copies/g, respectively) and all were negative for HuNoV GII and HAV. PMA pre-treatment and sequencing confirmed the absence of potential intact HuNoV GI particles on cranberries. None of the 150 blueberry samples tested positive for HEV. Overall, the prevalence of foodborne viruses in RTE cranberries and wild blueberries harvested in Canada is low, making these products relatively safe for consumers.

Comparison of the risk of infection of human rotavirus and astrovirus according to fishing and swimming activities at Las Cañas beach, Uruguay

AIMS

To estimate the risk of human Rotavirus (RV) and Astrovirus (HAstV) infections for swimmers and fishers at Las Cañas beach, Uruguay.

METHODS AND RESULTS

Surface water samples were collected monthly for one year. The dose response models used were β Poisson and ₁ F₁ hypergeometric for RV and HAstV, respectively. The probabilities of infection were calculated using a kernel density estimate to fitting the data and then sampling from this distribution (Monte Carlo simulation). The probability of RV infection for fishers was between 0 and 65% and for swimmers was between 0 and 50% (<18 years old) and between 0 and 38% (>18 years old). For HAstV, the probability of infection for fishers was between 0% and 45% and for swimmers was between 0 and 38% (<18 years old) and between 0 and 18% (>18 years old).

CONCLUSIONS

This study suggests that fishers are at higher risk of infection for both viruses when compared with swimmers mainly due to higher viral frequency and concentration at the site for fishing activities.

SIGNIFICANCE AND IMPACT OF THE STUDY

This study highlights the different risk of infection for Rotavirus and Astrovirus, determined according to two popular activities such as swimming and fishing evidencing their negative impact in public health when contaminated waters are used mainly in developing countries like Uruguay.

Inanimate Surfaces as a Source of Hospital Infections Caused by Fungi, Bacteria and Viruses with Particular Emphasis on SARS-CoV-2

The carriers of nosocomial infections are the hands of medical personnel and inanimate surfaces. Both hands and surfaces may be contaminated as a result of contact with the patient, their body fluids, and touching contaminated surfaces in the patient's surroundings. Visually clean inanimate surfaces are an important source of pathogens. Microorganisms have properties thanks to which they can survive in unfavorable conditions, from a few days to several months. Bacteria, viruses and fungi are able to transmit from inanimate surfaces to the skin of the patient and the medical staff. These pathogens include SARS-CoV-2, which can survive on various types of inanimate surfaces, being a potential source of infection. By following the recommendations related to washing and disinfecting hands and surfaces, and using appropriate washing and disinfecting agents with a broad biocidal spectrum, high material compatibility and the shortest duration of action, we contribute to breaking the chain of nosocomial infections.

Inactivation of hepatitis A virus and norovirus on berries by broad-spectrum pulsed light

Foodborne diseases are still a major global health and economic burden, and are mainly caused by viral pathogens, such as human norovirus and hepatitis A virus, which may remain infective for long times on food contact surfaces and on produce. The strategies of viral inactivation applied in the industry are not generally suitable for delicate foods such as berries. Brief exposure to high-intensity white light (UV to IR) has been shown to inactivate many bacteria. The effectiveness of this treatment against foodborne viruses on fresh produce is largely unknown. We show that pulsed light treatment causes a moderate drop in the luminosity (L*, which ranges from bright (high) to dark (low)) of blueberries (to 36.31 ± 0.99 from 42.47 ± 1.17) and affects the luminosity of lettuce slightly but does not affect the appearance of strawberries, blackberries or raspberries. Hepatitis A virus and murine norovirus 1 are thus reduced by 2 log cycles. Viral inactivation on blackberries was less effective. These results will help food industries evaluate the suitability of pulsed light disinfecting technology for specific fruits and vegetables.

Natural Products and Their Potential Anti-HAV Activity

The role of purified natural products in the prevention and treatment of countless diseases of bacterial, fungal, and viral origin cannot be overestimated. New antiviral drugs have been obtained from natural sources and transformed into preparations for prophylactic and therapeutic purposes. Flavonoids, polyphenols, saponins, proanthocyanins, polysaccharides, organic acids, proteins, polypeptides, and essential oils derived from plants, animals, or microorganisms can control and combat foodborne viral infections, including hepatitis A. The components of essential oils are characterized by numerous therapeutic and antioxidant properties and exhibit a broad spectrum of antimicrobial and antiviral activity. Due to these properties, they can be used to preserve meat, fruit, vegetables, and their products. Over the past two decades, much effort has been made to identify natural products, mostly of plant origin, to combat foodborne viruses. Natural plant extracts have several potential uses, not limited to increasing the safety of food products and improving their quality, but also as natural antiviral agents.

Application of virome capture sequencing in shellfish sold at retail level in Singapore

During the period from late 2019 to early 2020, we performed a foodborne virus detection from shellfish collected in Singapore at retail level. Multiple human enteric viruses were included as our targets including human noroviruses (NoVs) GI and GII, hepatitis A virus, hepatitis E virus and rotavirus. Out of the 60 shellfish samples, 23 (38·3%) were detected to be positive by reverse transcription-quantitative polymerase chain reaction (RT-qPCR) with human enteric viruses. Six samples were selected to proceed with virome capture sequencing with positive control samples spiked with serially diluted NoV GII clinical samples in oyster extract. As a result, the natural sample with comparable Ct values (34·0-35·0) of the spiked sample as detected by RT-qPCR generated much lower read counts (>7-log₂ cumulative sum scaling difference) and genome coverage (406 nt. vs 3715 nt.), suggesting that the RT-qPCR positive signals detected from the shellfish samples collected at the retail market were likely from degraded RNA derived from inactive virus particles.