Development and evaluation of an indirect ELISA for detection of exfoliative toxin ExhA, ExhB or ExhC produced by Staphylococcus hyicus.

Immunoblot analysis and enzyme-linked immunosorbent assay (ELISA) confirmed previous reports that the Staphylococcus hyicus exfoliative toxins ExhA and ExhB are metalloproteins, and further indicated that ExhC is also a metalloprotein. An indirect ELISA was developed for the detection of toxigenic strains as an alternative method to the use of phage typing for selection of S. hyicus isolates to be used in autogenous vaccine against exudative epidermitis in pigs. The indirect ELISA was evaluated by investigating the presence of toxin among a total of 655 S. hyicus isolates from 69 pig skin samples, one from each of the 69 pig herds with outbreak of exudative epidermitis. Toxigenic S. hyicus were detected in 74% of the cases by ELISA. From each of the five cases, in which initially no toxigenic S. hyicus were found, a further 40 S. hyicus-like colonies were tested in ELISA. Testing of this number of colonies has a >99% probability of disclosing toxigenic S. hyicus. Toxin-producing isolates were found in only two of the five cases investigated. This may indicate the existence of one or more variants of the exfoliative toxin of S. hyicus that are not detected in the indirect ELISA or that S. hyicus may be displaced from lesions of exudative epidermitis.