Normal Bacterial Agglutinins and their Significance

The agglutinative action of so-called normal serum upon certain species of bacteria has long been known, but no consensus has yet been reached as to how far these agglutinins are normal chemical constituents of the normal body or are specific antibodies that have developed in response to specific infections. As is well known, a similar question arises with respect to the significance of other antibodies such as diphtheria antitoxin and the neutralizing property shown by adult human serum for the virus of poliomyelitis. Several facts have been established. Biirgi' showed that the serum of different animal species varies in normal agglutinative power, that of cattle and horses, according to him, being relatively high, that of man, rabbits and guinea pigs relatively low. Similar observations have been made by Gibson2 and others, although minor differences have been noted in the ranking of species in order of agglutinative potency. It has also been observed that certain species of bacteria are more commonly agglutinated by normal serum than others. Thus Gibson found B. dysenteriae Y, the pneumobacillus and B. pyocyaneus highly susceptible to the agglutinating action of normal serum, the typhoid bacillus and B. dysenteriae Shiga less susceptible, while certain strains of B. coli were affected in very low dilution. With respect to the identity of normal and immune agglutinins various views are held, and there are numerous other points on which opinions are divergent. The observations recorded in this paper have been made with the purpose of throwing further light on the significance of these serum components. Technic.-Saline suspensions of living cultures have been used since they have given more uniform results than preserved antigens. The antigens were prepared from approximately 48 hour agar slant cultures of Brucella and from 24 hour cultures of the other bacteria used. Brucella strains were grown on 1% dextrose agar, typhoid and Sonne dysentery strains on veal infusion agar, and the other organisms on standard beef infusion agar. Platings were made at frequent intervals to insure uniformity in smoothness. A barium sulphate standard of medium opacity was used to standardize the density of the bacterial suspension. After addition of the serum to the antigen the tubes were incubated at 37 C. for 2 hours, then placed in the icebox overnight and read the following morning. Saline controls were always used.