Pathogenic Escherichia coli and enteric viruses in biosolids and related top soil improvers in Italy

To investigate the presence of genomic traits associated with a set of enteric viruses as well as pathogenic Escherichia coli in top soil improvers (TSI) from Italy.

Twenty-four TSI samples originating from municipal sewage sludges, pig manure, green and household wastes were analysed by real time PCR for the presence of hepatitis E virus (HEV), porcine and human adenovirus (HuAdV), norovirus, rotavirus and diarrhoeagenic E. coli. None of the samples was found positive for HEV or rotavirus. Four samples were positive for the presence of nucleic acids from human norovirus, two of them being also positive for HuAdV. Real time PCR screening gave positive results for many of the virulence genes characteristic of diarrhoeagenic E. coli in 21 samples. These included the verocytotoxin-coding genes, in some cases associated with intimin-coding gene, and markers of enteroaggregative, enterotoxigenic and enteroinvasive E. coli.

These results provide evidence that enteric viruses and pathogenic E. coli may be released into the environment through the use of sludge-derived TSI.

The results highlight that the TSI-related environmental risk for the food chain should be more deeply assessed.