The titration of therapeutic anti-typhoid serum

Abstract

An account has been given in a previous paper of the immunizing procedures now employed in the preparation of anti-typhoid serum in the horse for therapeutic use in man (Felix & Petrie, 1938). The object of the present communication is to describe the methods used for the titration of the serum.

The pathogenic and immunogenic activities ofSalmonella typhiin relation to its antigenic constituents

“…The cultures were preserved in waxed Lemco-agar stabs and were always grown on a trypsin-digest agar of good quality. The precautions to be taken in the preservation and maintenance of the cultures have been described in detail in a previous paper (Felix, 1938). When these precautions are carefully observed it is possible to maintain the antigenic composition of the different strains intact almost indefinitely.…”

“…The strain has been chosen for its outstanding ability to produce Vi antigen in maximum amount when grown on plain nutrient agar for periods of many years. (Felix, 1938).…”

“…typhi (Henderson & Morgan, 1938;Henderson, 1939a;Boivin & Mesrobeanu, 1938;Boivin, 1939 (Bhatnagar, Speechly & Singh, 1938). Nevertheless, cultures of this strain always contain a very small quantity of the H and the 0 antigen, readily detectable by the immunization of rabbits (Felix, 1938). TECHNIQUE (a) The maintenance of the cultures The cultures employed in the various tests were grown on a trypsin-digest agar of a pH of 7'4, transplanted daily, including Sunday, and kept in the incubator at 370 C. The necessity for carefully watching the quality of the agar medium and the constancy of the temperature at which the cultures are grown cannot be overemphasized.…”

“…Every agglutination and agglutinin absorption test included controls for saltagglutinability, made with the customary normal saline and with 2 5 and 5 % solutions of NaCl (see Felix, 1938). The controls were put up for each strain with the living suspension and also with a suspension heated for 2 hr.…”

“…The technique was the same as employed in earlier work (Felix, 1938). Cultures grown on trypsindigest agar slopes for not more than 16 hr., or for periods stated in the tables, were suspended in and further diluted with freshly prepared Ringer solution of a pH of from 7-6 to 7-4, the temperature of which had been brought up to 370 C. The bacterial content was determined by opacity, estimating each suspension three times in succession.…”