Infection of the Developing Chick Embryo with Dysentery Bacilli

The experimental approach to the problems connected with microorganisms of the Shigella group is greatly hampered by the lack of a convenient laboratory animal sensitive to this type of infection. The purpose of this paper is to report on our experiences with the infection of chick embryos with dysentery bacilli, which we hope may contribute toward the alleviation of this difficulty.

Goodpasture and his coworkers have studied bacterial infection in the chick embryo and have investigated the reactions of this new host. 1 , 2 , 3 There are also some reports from other laboratories on applications of this method to problems of a similar scope. 4-7

For our study we have used 2 strains of Shigella dysenteriae (“Shiga bacillus”), 7 of Shigella paradysenteriae (“Flexner bacillus”), and 7 of Shigella sonnei. All were carefully controlled for their microscopic, cultural and serological properties.

We found fertile eggs incubated 9 to 10 days most favorable for our purposes. We followed, in the main, Goodpasture's procedure. 8 , 9 If the usual precautions of bacteriological work are applied, the danger of contamination of the eggs is certainly not greater than that of agar plates.

The number of viable microörganisms introduced was checked by plate count of 10^-7 dilutions of the broth culture. On the average the broth cultures contained 500,000,000 microörganisms per ml. The eggs were infected by dropping 0.1 ml amounts of broth diluted serially 10-fold with saline solution upon the chorio-allantoic membrane. The infected eggs were incubated at 37.5°C.