Swine salmonella ab test

Sera from sows (Large White × Landrace) at a university-owned pig farm in Lower Austria were tested by the IDEXX Swine Salmonella Ab test (IDEXX Europe, Hoofddorp, The Netherlands) prior to the study. The five sows with the lowest sample to positive control (S/P) ratios (S/P ratios: 0.295–0.473, cut-off for positivity: 1.0) were selected and 44 female and male castrated pigs (Large White × Landrace × Pietrain) from those sows were included in the study at the age of four weeks. All piglets underwent routine vaccinations against PCV-2 (Ingelvac CircoFLEX^®, Boehringer-Ingelheim, Ingelheim am Rhein, Germany) at three weeks of age and Mycoplasma hyopneumoniae (M⁺PAC^®, MSD Animal Health, Kenilworth, NJ, USA) in the first and third week of life at the farm. The Salmonella-free status of the piglets at the start of the study was validated by serological testing for Salmonella-specific antibodies by the IDEXX Swine Salmonella Ab test (IDEXX Europe) and by microbiological testing of fecal samples collected on three consecutive days after arrival (study days (SD) −11, −10, −9). Antibody S/P ratios were below the positivity cut-off for piglets (0.25). Additionally, no Salmonella were detectable in the fecal samples of the piglets at the stated time points.

Serum was obtained after centrifugation of blood samples for 10 min and 1,900 × g at room temperature. For the detection of Salmonella-specific antibodies, serum samples were tested using a commercially available ELISA kit (IDEXX Swine Salmonella Ab Test, IDEXX Europe, Hoofddorp, The Netherlands) according to the manufacturer’s instructions. Results were recorded as S/P ratios determined by the ratio between mean optical density (OD) of each sample and mean OD of the positive control. According to the manufacturer’s recommendations, S/P ratios < 0.25 were defined as negative and samples ≥ 0.25 as positive.