Reappraisal of the Berg method to assess viral contamination of the soil

Abstract number: 1733_1056

Bianchi S., Amendola A., Canuti M., Zappa A., Tanzi E., Koncan R., Cornaglia G.

Objectives: Some viruses are able to contaminate the soil and persist in it. Nevertheless, at present, no widely accepted standards exist for the evaluation of viral contamination in this environment. The recent scientific literature is not particularly informative, since most studies on this subject date back to roughly 30 years ago and focus on soil contamination by sewage and on controlling the circulation and transmission of oro-faecal agents. The Berg method was developed in 1980 for `recovering viruses from sludges', and the following years did not witness any evolution in that technique or its application to other types of viral contamination. Thus, we have re-examined it in order to extend its applicability to soil.

Methods: Known amounts of enteric viruses (namely Coxsackie B6 virus and Echovirus 12) were used to infect the dry soil. The viral particles were subsequently eluted with 10% beef extract, by means of centrifuging and serial passages through 3-mm, 0.45-mm and 0.22-mm filters, respectively. All tests were performed in the absence of sterility and under standardised environmental conditions, namely aerobiosis, 23°C and pH 7. Following every step of the elution procedure, the presence of the virus was tested by means of gene amplification assays specific for the enteroviruses used. The viability of the viruses in the eluates was assessed on the basis of their cytopathic effect on permissive cells (human rhabdomyosarcoma cell line RD).

Results and Conclusions: Optimal parameters were identified as regards quantity of soil and beef extract (100 g and 100 mL, respectively). Titration of the filtrates obtained from each single step made it possible to assess the efficiency of viral recovery, which exceeded by 50% that envisaged in the original Berg method (reported recovery values, 35–40%). The application of this revised technique to the soil may permit effective monitoring of different viruses with alleged high environmental resistance.

Session Details

Date: 31/03/2007
Time: 00:00-00:00
Session name: European Society of Clinical Microbiology and Infectious Diseases
Location: ICC, Munich, Germany
Presentation type:
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