Identification of Corynebacterium diphtheriae by immunofluorescence during a diphtheria epidemic

During a large epidemic of diphtheria, the technique of immunofluorescence was applied to specimens obtained from 310 patients, 77 of whom were diagnosed clinically as having the disease. The technique made use of commerical fluorescent antisera prepared against the somatic antigens of Corynebacterium diphtheriae. The results obtained by immunofluorescence of slides prepared directly from swabs were found to be unsatisfactory but when the swabs were subjected to prior incubation in a growth medium the results of immunofluorescence and bacterial culture agreed in 95% of specimens. Immunofluorescence applied to bacterial colonies obtained on primary isolation agreed completely with definitive bacterial identification. These two methods for the rapid identification of C. diphtheriae appeared to be as reliable as formal cultural and biochemical methods and could be usefully and economically applied to the examination of large numbers of clinical specimens during an epidemic.