Notes On The Vi Antigen Of Bacillus Typhosus

Abstract

a series of sporadic cases of enteric fever in Khartoum during the latter part of 1934 and 1935 afforded an opportunity of examining certain claims advanced in these papers. As the following observations on various aspects of the subject have been carried out over a period of 18 months the results are inevitably somewhat scrappy, but in view of the importance of the subject it was thought that they might not be altogether without interest for other workers.As a strictly chronological record would be somewhat confusing the results obtained are grouped under the main points investigated.When the work was commenced no inagglutinable cultures of local strains of B. typhosus were available, and such cultures were kindly supplied by Dr A. Felix and Major H. J. Bensted, to both of whom the author is much indebted for their assistance. PRESERVATION OF CULTURESTo avoid as far as possible too many subcultures, the method of infected mouse spleen dried in vacuo over calcium chloride as recommended by Perry et al. .(1934) was followed, the only difference being that the white rat was used in place of the mouse, the latter not being available. It may be stated here that young white rats seem to be equally susceptible to virulent strains of B. typhosus as mice. The method has given excellent results, the claim of these authors that cultures could be obtained after 4 months being confirmed, and when tested on young rats the organisms seemed to have lost none of their virulence and inagglutinability by 0 serum. As no ascitic fluid was available, Kauffmann's method (1935b) of passage of cultures through complement and growth on fresh ascitic agar was not tried, but it seems to offer no particular advantages at least to workers in dusty tropical countries. Where no mention otherwise is made all agglutination tests were carried out with lving suspensions in saline from agar cultures of 18-20 hours old. The macroscopic technique was used in all agglutination tests, incubation being carried out in a water bath for 4 hours at 370 C. and the results were read after standing at room temperature for 22-24 hours.

A Vi variant ofSalmonella typhiand its application to the serology of typhoid fever

“…SINCE the description of the new typhoid Vi antigen and its corresponding antibody by Felix and his co-workers, various studies have appeared on this subject confirming their observations (Kauffmann, 1935a, b;Dyachenko, 1936;Horgan, 1936;Craigie & Brandon, 1936a, b;Robertson & Yu, 1936;Almon & Stovall, 1936;Bensted, 1937;and others). The presence of Vi antigen in a typhoid strain can be inferred from its 0 inagglutinability and confirmed by agglutinating it against a pure Vi serum.…”

“…The explanation would appear to be the unsuitability of Lab Lemco and other meat extracts as nutrient agents for the routine growth of the organisms of this group. The deleterious effect of such artificial media on the antigenic complex of the highly virulent strains of typhoidparatyphoid group has already been commented on by various observers (Horgan, 1936;Bhatnagar et at. 19376;Bensted, 1937).…”

The agglutinins of typhoid carriers

“…Gundel & Abdoosh (1936) had 1 positive of very low titre (1:10) amongst 21 typhoid sera, and 1 good positive amongst 11 convalescents. In 100 normal sera Horgan (1936) found traces in a serum dilution of 1: 10 six times only, and in 28 typhoid patients, by means of repeated examinations, Vi agglutinin was found in a small number only. Our own observations on Vi agglutinins in patients and convalescents are rather similar to those quoted.…”

The Significance of the Vi Antigen

“…Early work with heat-killed cultures failed to demonstrate Vi agglutinin production in rabbits, but with refinement in methods of detecting the antibody we have found it in some of our rabbit antisera, and Horgan (45) reports it also. Early attempts to demonstrate the antibody in human sera following vaccination likewise failed (10,24); but unpublished results of work at this laboratory have shown that if blood is drawn at the right time, such vaccinated individuals may sometimes reveal it.…”