Statistical correlation between enterovirus genome copy numbers and infectious viral particles in wastewater samples.

AIMS: Classic virological tests are time consuming and labour-intensive; real-time RT-PCR has proven to be a fast method to detect and quantify enterovirus genomes in clinical and environmental samples. This method is unable to discriminate between infective and noninfective enterovirus particles; few clinical studies have compared real-time RT-PCR and viral culture. We wondered if the enterovirus genome quantification could be correlated to the infectivity. METHODS AND RESULTS: We used the statistical approach to verify our hypotheses to correlate data, obtained by the standard method (most probable number of cytopathic units-MPNCU) and molecular test (real-time RT-PCR), on wastewater treatment plant samples. Chi-squared test was used, considering several cut-off values ('50'-'100'-'200' genome copy numbers), to determine statistical significance in comparison of the two methods. Chi-square value was not significant when cut-off of 50 (P = 0.103) and 100 (P = 0.178) was assumed but was significant with cut-off of 200 (P = 0.044). CONCLUSION: This limit, 200 genome copy, could be used as cut-off value to indicate enterovirus survival in environmental monitoring. SIGNIFICANT AND IMPACT OF THE STUDY: To introduce a fast procedure that is able to compensate for disadvantages of cell culture method for viral environmental analyses.

Presence and environmental circulation of enteric viruses in three different wastewater treatment plants.

AIMS: The aim of the work was to evaluate the circulation of the viruses and to determine a correlation between faecal indicators and viruses. METHODS AND RESULTS: Raw wastewater and effluent samples were collected from three wastewater treatment plants, during three sampling periods, and analysed, using cultural and molecular methods, to determine bacteria and virus presence. The results show a removal of bacterial indicators, but a limited reduction of the phages. The viral analysis displays the circulation of cultivable enteroviruses and differences in the seasonal-geographical distribution. Hepatitis A virus was found with only two genotypes: IA-IB. Rotavirus was present in 11.11%, 24.14%, 2.78% of the samples in the 1st, 2nd and 3rd sampling periods; Astrovirus in 33.33%, 6.9%, 25%; Adenovirus in 7.41%, 3.45%, 2.78%; Norovirus in 7.41%, 10.34%, 5.56% respectively. Adenovirus was never identified in plants B and C as Rotavirus in plant C. CONCLUSIONS: The presence of faecal indicators was not predictive of the enteric virus presence, whereas a different circulation of Enteroviruses was found in the wastewater treatment plants. SIGNIFICANCE AND IMPACT OF THE STUDY: The study shows the importance and the usefulness of molecular methods to evaluate the virus circulation and the genetic variability of Enteroviruses.