AGGLUTINABILITY OF BLOOD AND AGAR STRAINS OF THE TYPHOID BACILLUS

The growth of the typhoid bacillus on an agar-medium containing 10 per cent.defibrinated rabbit blood, which we have found of advantage in our experiments, differs in certain respects from the growth on plain agar.We have already noted that the blood-agar cultures are more abundant.A concrete example of the amount of growth produced on each medium may be drawn from certain of our vaccine preparations to be more fully described later.To produce growths of Bacillus typhosus for immunizing vaccines we inoculate one-quart Blake bottles containing 100 c.c. of medium with a few cubic centimeters of a twenty-four-hour bouillon-culture of the organism.In one experiment nine Blake bottles of 2 per cent.agar were inoculated with a plain bouillon-culture of B. typhosus No. 3; at the same time, nine Blake bottles of 10 per cent, bl ood\x=req-\ agar were inoculated with a blood-bouillon culture of B. typhosus No. 3b.After incubation at 37 C. (98.6 F.) for two days, the collected agar and blood-agar growths were suspended each in 220 c.c. of normal saline, filtered through cotton and precipitated with 300 c.c. of absolute alcohol.After eentrifugalization, the separate precipitates were again centrifugalized and dried over sulphuric acid for two days.These dried cultures were ground and weighed with the following results : Blood-growth, 0.675 gm. ; agar-growth, 0.36 gm.It will thus be seen that the growth of the organism is almost twice as abundant on 10 per cent, blood-agar as on plain agar.Not only is the growth of the blood organism more abundant, but its morphology differs distinctly from the agar-strain.When exam¬ ined in hanging-drop preparations, the blood-strain of the typhoid bacillus is larger, thicker and tends to grow in chains.It remains, how¬ ever, quite as motile as the agar variety.Associated with the morphological change that the organism under¬ goes when grown on rabbit blood, and we believe in some way dependent on it, are certain distinct and important variations in the agglutinability of these organisms by antityphoid serum.The ultimate identification of bacilli isolated from the blood-stream of suspected typhoid-carrier rabbits