Bacteriological studies.

  • Great Britain. Ministry of Health
Date:
1923
Catalogue details

Licence: Public Domain Mark

Credit: Bacteriological studies. Source: Wellcome Collection.

    70/74 (page 64)
    but all grow less strongly in subculture and readily die out both on Loffler’s and on Dorset’s medium, whereas the diphtheria bacillus on the latter is long-lived and persists without subculture for many months. All, of course, are non-toxigenic and all fail to grow anaerobically in deep glucose agar shake cultures, whereas the typical strains, whether virulent or avirulent, grow - well under such anaerobic conditions. The bacilli (1) and (3) (Hoffmann and saccharose fermenters) have given clear negatives with all my agglutinating sera and are thus readily distinguished by serological reactions. But with the ‘“‘ xerosis ’’ bacilli confusing results occur ; with Serum III, and more particularly with Serum IV, well-marked agglutination can be obtained with these strains in dilutions as high as 1 in 100. I have prepared an agglutinating serum with one of these ‘““xerosis ’’ strains which after 7 months immunisation aggluti- nated it in the form of fine floceuli at 1 in 1,600 dilution. This serum produced a similar agglutination with 17 other similar strains (chiefly from the noses of healthy school children). With diphtheria bacilli, on the other hand, it produced no more than traces of agglutination. It seems probable that these “‘ xerosis ”’ bacilli from the nose belong to one species, since all those tested agglutinated well with this xerosis serum. Further, it seems possible that this species is more nearly related to the diphtheria bacillus than any of the other diphtheroids—perhaps as nearly as the B. paraty- phosus to the B. typhosus—although possessing none of its power of producing the characteristic toxin. It is of interest that the diphtheria bacillus Strain IV, which appears to possess some of the antigen producing agglutinin for the xerosis type, is itself more nearly related to this type (a) morphologically, in that its cultures have a preponderance of long barred bacilli, and (6) culturally, in that it grows feebly on ordinary serum-free media. 4 SIGNIFICANCE OF ANTIGENIC DIVERSITY. What reason can be given for the diversity in antigenic composition of different diphtheria bacilli? In the case of other bacteria this diversity in different strains of one species may be plausibly interpreted as a response to the gradually extending anti-bacterial activities of the host species and may come about by a process of survival of the variant bacteria. But one might have expected that the possession of a specific toxin of unvarying composition (Hartley) and indiscriminate potency for the host might save the diphtheria bacillus from the necessity for such adaptation, especially as the local effects of its toxin appear to form an essential condition for the extension of infection in the tissues. It is evident, on the contrary, that the diphtheria bacillus is just as subject to antigenic variation as the meningococcus, the pneumococcus or the influenza bacillus, which likewise occupy the mucous membranes of the mouth,