Preliminary studies on the antigenic properties of different strains of bacillus typhosus

Abstract

A search through the literature reveals no report of special work upon antigenic differences among typhoid strains, although serologic methods have frequently been used in differentiating typhoid from closely allied organisms. The demonstration of the severally specific antigenic individualities, notably of strains of pneumococci, streptococci, gonococci, meningococci, and influenza bacilli; the fluctuant epidemiologic severity of typhoid fever from time to time; the observation that antityphoid inoculation confers no protection against paratyphoid infection; the growing list of instances in which antityphoid inoculation has been unsuccessful, the previously known and personally confirmed fact that a polyvalent antigen is essential for good alexin fixation reactions in typhoid fever are the main facts which have led to this investigation.

Attention has been focused chiefly upon the delicately specific method of alexin fixation as a means of detecting antigenic differences. A considerable number of confirmatory agglutinin absorption experiments have also been performed.

Materials and Technic.-Of the 48 strains which have been used 21 are laboratory strains two to fifteen years old, and the rest have been isolated and authenticated during the past year by Gay and Chickering in the course of studies of local cases of typhoid fever.

The antigens used were washed, formalized suspensions of typhoid bacilli. These suspensions have been used also for immunizing rabbits, being eminently satisfactory for this purpose as agglutinogens for agglutination and absorption tests. The total volume of the fixation test has been one cubic centimeter, one fifth that of the classical Wassermann. Sheep cells, rabbit anti-sheep hemolysin, and guinea-pig serum make up the hemolytic system which has daily been balanced by simultaneous alexin and hemolysin titrations. Pooled serum from six or more guinea pigs has been preserved by salting for alexin, a method which has many advantages.