Staining bacterial smears with fluorescent antibody. III. Antigenic analysis of Salmonella typhosa by means of fluorescent antibody and agglutination reactions.

Moody et al. (1956) and Thomason et al. (1956) have applied fluorescent antibody techniques to the specific detection of Malleomyces pseudomallei in dried smears. This method already has proved successful for the detection and identification of several other pathogenic bacteria. It is potentially a valuable tool for the identification of pathogenic bacteria in clinical specimens and should be of interest to clinicians and bacteriologists in public health and hospital laboratories. Experience with the use of fluorescent antibody for the detection of bacteria has shown the need for more basic information regarding the nature and specificity of the reaction. The antigenic constitution of cells of a given species of bacteria may vary both quantitatively and qualitatively, depending upon the medium on which the cells have been cultured and upon the physicalchemical manipulations to which they have been subjected, and upon natural variation from unknown causes. In order to analyze the influence of the different classes of antigenic cell constituents upon staining by fluorescent antibody, a model system was sought. Salmonella typhosa seemed to qualify in this respect, since its serological characteristics are well-known and since it contains components representing three common classes of antigens, i. e., the K or envelope antigens (Vi), the flagellar or H antigens (d), and the somatic or 0 antigen (9, 12). The fact that each of the specific antigens, (Vi), (9, 12), and (d) is found in bacteria which have no other serological relationship to S. typhosa makes it possible to prepare individual sera containing antibody for each class of antigen found in the typhoid organism. By this approach it has been possible to show that three classes of antigens present in smears of cells of S. typhosa may be stained specifically with fluorescent antibody and that this specificity is roughly equivalent to that demonstrable by the agglutination test.