SEROLOGICAL IDENTIFICATION OF SHIGELLA FLEXNERI BY MEANS OF FLUORESCENT ANTIBODY

Publisher Website
Google Scholar
Abstract
The fluorescent antibody technique has been employed to group and type Shigella flexneri in pure culture. When the direct staining procedure was used the staining reactions were of the same specificity as those of the slide agglutination method. All S. flexneri serotypes were stained by labeled Shigella group B antiserum but not by antisera against Shigella groups A, C, or D. The degree and number of cross staining reactions between various S. flexneri serotypes and their labeled unadsorbed antisera was tested. In general, serotypes with common group factor antigens were both agglutinated and stained by labeled Flexner antisera containing antibodies against homologous group factor antigens. A few instances were noted where cross agglutination reactions occurred but staining was absent. Tube agglutination tests revealed that a cross agglutinin titer of 1:160 was necessary to give a good cross staining reaction. Heterol-ogous agglutinin titers lower than this gave variable cross staining reactions. S. flexneri antisera rendered type-specific (slide agglutination) by appropriate adsorptions with heterologous Flexner serotypes stained only the homologous serotypes. Attempts to identify S. flexneri in fecal specimens obtained from experimentally infected guinea pigs were only partly successful. When labeled Shigella grouping sera were employed diagnosis could not be made with any degree of accuracy when the numbers of Shigella organisms was small since, on occasion, group A and C antisera stained significant numbers of morphologically similar organisms in the feces of normal guinea pigs. When labeled S. flexneri were employed, nonspecific staining was not observed. The significance of these results, with respect to utilization of fluorescent antibody methods as a diagnostic tool in enteric infection is discussed.