The Effect of Desiccation on Antigenic Structure

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Abstract
SUMMARY: Two different organisms were dried in normal rabbit serum and in the presence of specific antibody. Reconstitution of the dried products showed that the presence of antibody did not affect the viability, agglutinability or the absorptive capacity of the bacteria. Drying by sublimation has become a routine method of preserving bacterial cultures. Although criticism is seldom made in print, several workers who do not themselves dry their cultures suggest that in the drying process there may be a selective killing, or change of unidentified characters, particularly those of an antigenic nature. In the last four years more than a thousand strains of bacteria have been dried in the National Collection of Type Cultures, and the cultural characters before drying compared with those after drying. The morphological and bio- chemical characters have never shown any significant change, but some strains have shown an apparent increase in rough-surfaced colonial forms after drying. Most of the strains were dried in filtered horse serum, and it was thought that occasionally a culture might be suspended and dried in the presence of anti- body in the so-called normal serum. It seemed unlikely that drying in the presence of antibody would have any effect on the organism, though sub- sequent growth in the reconstituted serum might increase the proportion of R-forms. Experiments were planned to furnish evidence on this point and cultures were dried in the presence of high titre antibody. MATERIALS AND METHODS Strains. A paracolon organism (NCTC 8535, M.R.C. Standards Laboratory strain 3915) with the a-antigen (Stamp & Stone, 1944), and a strain of a salmo- nella species (NCTC 6759) with the antigenic formula 1, 3, 19:i+-+z, were used. Antisera. The antisera, prepared in the M.R.C. Standards Laboratory were kindly supplied by Lt-Col. H. J. Bensted. The a-antiserum had a titre of 1/20,000. The salmonella 0 serum had titres of l/lOOO and 1/5000 in two successive bleedings.
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