Evaluation of the Copan flocked swab with UTM-RT medium for antigen detection of HSV, direct immunofluorescence of RSV and viral culture of HSV

Abstract number: P1911

Vijgen S., Nys S., Cartuyvels R., Magerman K.

Objectives: Successful preservation of viral viability and antigens depends on specimen collection, transport and preservation system used. In this study, the newly developed nylon-flocked swab with universal transport medium (UTM), specially designed to optimise specimen collection and to minimise entrapment of the microorganisms, was compared with the Copan virus transport system for antigen detection of HSV-1, direct immunofluorescence of RSV and viral culture of HSV-1.

Methods: Viral culture of a PCR-confirmed HSV-1 positive clinical sample was harvested and serially diluted in MEM 2% culture medium (CAMBREX).

The Copan flocked swab with UTM-RT medium (UTM, Copan, 395C) and the virus transport system (VTS, Copan 147C) were inoculated in 100 mL of each dilution and preserved respectively at room temperature or 4°C for 2 hours. Each swab was inoculated on the cell lines A459, MRC-5 and Hep2 and controlled daily for the cytopathogenic effect of HSV-1. The serial dilutions of the positive clinical sample were used as a positive control.

For the antigen detection and direct immunofluorescence, 500 mL of the UTM cell suspension was pelleted, washed and resuspended in PBS. Twenty microliters of this final suspension was stained using standard procedures.

Results: The MRC-5 and A549 cell lines inoculated with samples of the UTM swab showed a cytopathogenic effect as soon as the positive control wells. Also, dilutions of UTM were sooner positive as compared to VTS. These differences were less clear in the Hep-2 cells.

There were no significant differences in results of HSV-1 antigen detection and direct immunofluorescence of RSV with UTM compared to VTS. However, the yield with UTM was higher as compared to VTS, even at low viral loads.

Conclusion: The flocked swab with UTM-RT medium showed an overall better recovery of HSV-1 after culture. Furthermore, the flocked swab seems to have a greater diagnostic sensitivity in the HSV-1 antigen detection and RSV direct immunofluorescence.