Abstract
In a large comparative survey of Danish and Swedish slaughter pig herds performed prior to this work, it was unexpectedly found that some Swedish herds harbored seropositive pigs. Serum samples from the Swedish herds had moderate responses in the Salmonella rnix-ELISA (detecting serogroup B and C I infections) compared to the Danish herds classifying some of them as seropositive using a cut-off value at 40 OD%. In Sweden, extensive Salmonella control is carried out by bacteriological screening of feces and lymph nodes, and the overall prevalence has been proven to be below 0.1%. The serological positive results were therefore unexpected; hence the reactivities of the Swedish sera were studied by a number of immunochemical analyses (Western blot, indirect ELISA, inhibition ELISA, avidity ELISA) and compared to sera from Danish pig herds with verified Salmonella infections ("the reference sera"). In Western blot, the Swedish sera had high binding reactivities against Salmonella Typhimurium LPS of different molecular weights, and gave binding patterns similar to that of the reference sera. Pre-incubation with free S. Typhimurium LPS or PS (the polysaccharide part of LPS) was able to inhibit the reactivity of the Swedish sera in the mix-ELISA. Reactivities against other related bacterial LPS such as Citrobacter freundii LPS and Yersinia enterocolitica 0:3 LPS were observed in the Swedish sera, but these LPS antigens were unable to inhibit the reactivities in: the m_ix-ELISA as efficiently as S. Typhimurium LPS. Furthermore, the Swedish sera did not bind Salmonella LPS of another serogroup (S. Meleagridis LPS, serogroup El) or rough Salmonella LPS, both lacking the specific O-antigenic parts of S. Typhimurium LPS. The avidity of the Swedish sera was much lower than the avidity of the reference sera, which could indicate the presence: of transient low-dose infections or stimulation by inactivated bacteria in. feed. The results obtained in this investigation strongly indicate that the Swedish sera contain antibodies directed against the O-antigenic part of LPS from S. Typhimurium or possibly on as yet unknown bacterium.
Original language | English |
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Journal | Veterinary Microbiology |
Volume | 85 |
Issue number | 1 |
Pages (from-to) | 69-82 |
ISSN | 0378-1135 |
DOIs | |
Publication status | Published - 2002 |
Keywords
- Salmonella Typhimurium
- LPS
- antibodies
- immunochemical analyses