Detection of antibodies to Streptobacillus moniliformis in rats by an immunoblot procedure.
An immunoblot (IB) technique for detecting antibodies to Streptobacillus moniliformis in rat sera was evaluated. Immune sera to three S. moniliformis strains showed a similar reactivity pattern with both autologous and homologous antigens in the 18-87 kDa range. Using a rat S. moniliformis strain as the antigen, a similar reactivity pattern was found with sera from rats infected experimentally with S. moniliformis and sentinels. Two to five proteins were detected in the 32-55 kDa range. Over a period of 2.5 years, 27/133 rat serum panels submitted for routine monitoring yielded one or more S. moniliformis enzyme-linked immunosorbent assay (ELISA)-positive samples. In one of these 27 panels, sera showed an IB reactivity pattern resembling that observed with immune sera and with sera from infected and exposed rats. S. moniliformis was confirmed in the colony by both culture and polymerase chain reaction (PCR). Sera from the remaining 26 ELISA-positive serum panels frequently showed activity to a 57 kDa antigen but not more than one antigen was detected in the 32-55 kDa range. We conclude that the IB can be used as a confirmatory test for the detection of S. moniliformis infection in ELISA-positive rats.