Further Studies of Agar-slant Tissue Cultures of Typhus Rickettsiæ. ∗

Abstract

In a preliminary note published in these Proceedings, 1 the writers described an agar-slant-tissue method for the cultivation of Rickettsiæ, both of the murine and of the classical types of typhus fever.

Further study of this method has led to modifications and standardizations which are reported herewith in order to facilitate its use in the hands of others. Preliminary experiments by Pinkerton with Rocky Mountain Spotted Fever virus indicate a possibility that the method may be successful with Rickettsiæ other than those of typhus.

The medium as now used differs from the original only in proportions of ingredients. We have found that results are most regular when the agar is prepared as follows:

A “Tyrode” solution of the ordinary formula is made up double strength throughout, except that only 1 gm. of bicarbonate of sodium is used per liter. The agar used is a Difco granular Bactoagar.

A mixture of 150 cc. double strength Tyrode and 150 cc. of horse serum with 8 cc. of phenol red solution is filtered through a Seitz filter.† To the filtrate is added 150 cc. of 4% agar in distilled water, cooled to 45°C.