Development of a serologic panel for the recognition of nocardial infections in a murine model

A murine model was used to develop a sensitive and specific serologic test for clinical and subclinical infections caused by Nocardia. The following tests were used: (a) enzyme-linked immunosorbent assays (ELISAs) with culture filtrate and cytoplasmic extract antigens from Nocardia asteroides; (b) ELISA with N. asteroides trehalose dimycolate (cord factor); (c) indirect immunofluorescent antibody assay with whole cells of N. asteroides; and (d) Western-blot analysis for the 54 to 55-kD, 35-kD, and 62-kD proteins of N. asteroides. The sera from BALB/c mice, experimentally infected with nonlethal doses of three species of Nocardia, nine species of Mycobacterium, Rhodococcus equi, two species of Actinomadura, and two species of Streptomyces were tested using this panel. The serologic tests did, indeed, identify mice infected with nocardiae and could differentiate them from mice infected with the other actinomycetes, including mycobacteria.