Abstract
Several studies have shown that enteric viruses can be transferred onto the surface of vegetables and fruits through spray irrigation, but, recently, reports have suggested viral contamination of vegetables sub-irrigated with reused wastewater. Hydroponic cultures, used to grow ready to eat fresh lettuce, have also been used to study the possibility of viral absorption through roots. This study was conducted to assess a possible risk of viral contamination in lettuce from contaminated water. The leaves of lettuce plants grown in hydroponic cultures where the roots were exposed to water containing Coxsakievirus B2, were analysed for evidence of the virus. The plants and water were sampled at different times and virus was measured using quantitative RT-PCR and infectivity assay. In leaf samples, the lowest observed infective data were lower than the qRT-PCR detection limits, suggesting that free viral RNA or damaged viruses are eliminated rapidly while infectious particles remain stable for a longer time. The obtained data revealed that the leaves were contaminated at a water concentration of 4.11 ± 1 Log Most Probable Number/L (8.03 ± 1 Log GC/L) a concentration observed in contaminated untreated water of wastewater treatment plants. However, the absorption dynamics and whether the virus is inactive in the leaves still remains to be clarified. Nevertheless, this work has practical implications for risk management in using reclaimed water for agricultural use; when irrigated vegetables are destined for raw consumption, virological contamination in water sources should be evaluated.
Highlights
Epidemiological evidence indicates that enteric viruses are a growing cause of foodborne illnesses in developed countries [1]
The results were expressed as the number of genomic copies per liter (GC/L) for the nutrient solution and the number of genomic copies per gram (GC/g) for the leaves
According to the results of the qRT-polymerase chain reaction (PCR) analyses, the viral titres of the water at the starting point of the experiment were similar to the expected values
Summary
Epidemiological evidence indicates that enteric viruses are a growing cause of foodborne illnesses in developed countries [1]. This technique only provides information about whether viral genomes are present, not about the viability of viruses This analytical technique could be important for assessing the risk of biological contamination in vegetables and establishing concentration limits for the irrigation water. As other enteric viruses chosen for the same aim by several authors [6,13], enteroviruses are pathogenic and small This could facilitate their internalization through plant roots, and they have surface characteristics similar to noroviruses [35]. With these viruses, the same sample can be analysed both with cultural and biomolecular methods without the use of surrogates, permitting the study of different inactivations of genome and infective particles at the same time and experimental condition
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