title: Detection of anti-listeriolysin O in dairy cattle experimentally infected with Listeria monocytogenes.
abstract: A dot-blot assay and an enzyme-linked immunosorbent assay (ELISA) to detect listeriosis in dairy cattle were developed that detected anti-listeriolysin O antibodies in the serum of cows experimentally infected with Listeria monocytogenes. The tests utilized purified listeriolysin O (LLO) as the detection antigen and streptolysin O (SLO) to absorb cross-reacting antibodies. The two tests were compared with an agglutination test that used formalin-killed whole L. monocytogenes cells. Blood samples were collected periodically from 17 cows after intramammary gland infection, and the development of anti-LLO antibodies was followed by an agglutination test, the dot-blot test, and the ELISA. In general, an agglutination titer of > 640 was needed for a positive dot-blot anti-LLO test for nonpregnant cows. However, 1 pregnant cow with an agglutination titer of 20 was positive in the dot-blot test. The ELISA was as sensitive as the dot-blot assay but gave a quantitative measurement to distinguish serum samples of positive reactors from cross-reactors. The specificity of the LLO-based tests was further evaluated using serum from cows that had been experimentally infected with Staphylococcus aureus, 17 of which had agglutination titers for L. monocytogenes > 640. These elevated agglutination titers were probably due to cross-reacting bacterial antigens because serum from 9 of 17 of these animals did not react to the purified LLO antigen. A positive response to the LLO-based dot-blot and ELISA assays is indicative of previous or current infection with L. monocytogenes.
authors.affiliation: Physiopathology Research Unit, US Department of Agriculture, Agriculture Research Service, Ames, IA 50010, USA.
authors.forename: A L
authors.initials: AL
authors.lastname: Baetz
authors.forename: I V
authors.initials: IV
authors.lastname: Wesley
mesh_terms: D000372:Agglutination Tests; D000818:Animals; D000907:Antibodies, Bacterial / Q000097:blood*; D001427:Bacterial Toxins; D002417:Cattle; D003429:Cross Reactions; D004797:Enzyme-Linked Immunosorbent Assay / Q000379:methods / Q000662:veterinary; D005260:Female; D006360:Heat-Shock Proteins / Q000276:immunology*; D006460:Hemolysin Proteins / Q000276:immunology*; D008089:Listeria monocytogenes / Q000302:isolation & purification*; D008088:Listeriosis / Q000097:blood / Q000276:immunology*; D008321:Mammary Glands, Animal / Q000382:microbiology; D011247:Pregnancy; D012680:Sensitivity and Specificity
chemical_list: D000907:Antibodies, Bacterial; D001427:Bacterial Toxins; D006360:Heat-Shock Proteins; D006460:Hemolysin Proteins; C038705:hlyA protein, Listeria monocytogenes