A Comparison by Means of the Complement-Fixation Test of the Relative Potencies of Chloramphenicol, Aureomycin, and Terramycin in Experimental Q Fever Infections in Embryonated Eggs

In the course of screening a series of compounds for anti-rickettsial activity, a procedure was investigated which takes advantage of the complement-fixation test as a means of estimating rickettsial growth in chick embryos. The anti-rickettsial activity of compounds has previously been assessed in infected chick embryos either by measuring the increase in prolongation of life or by determining the infectiousness of the yolk sacs of treated embryos at various times after treatment or by a combination of these two methods (1–6). The anti-rickettsial effectiveness of compounds has also been estimated in terms of the numbers of organisms observed in stained smears made from infected tissues (7, 8). These methods have their limitations and defects. A test for antibiotic activity should measure, as directly as possible, the effect of the test substance on the numbers of organisms present at any time following treatment, as compared with the untreated controls.