Evaluation of immunomagnetic separation in combination with modified semi-solid Rappaport Vassiliadis medium and Rambach agar for the isolation of Salmonella

Abstract

The ability of polymagnetic beads coated with Salmonella antibodies to enhance detection of Salmonella using Modified Semi-solid Rappaport Vassiliadis (MSRV) medium and Rambach agar was evaluated. Inoculation of the MSRV medium with pre-enriched buffered peptone water (BPW) resulted in the isolation of Salmonella from 60% of raw poultry samples. Capture of the Salmonella with the beads and inoculation of the beads onto MSRV medium resulted in the isolation of Salmonella from 62% of the samples. If the pre-enriched BPW was centrifuged and the pellet was resuspended in 1 ml of BPW before capture of the Salmonella with the beads and inoculation of the beads onto MSRV medium, Salmonella were isolated from 65% of the samples. Direct plating of the beads to Rambach agar after capture of Salmonella from the pre-enriched BPW, but without selective enrichment in the MSRV medium, resulted in low recovery rates of Salmonella. Plating of pure cultures of Salmonella belonging to subspecies IIIa and IIIb onto Rambach agar resulted in colonies with an atypical appearance.