Use of the Chick Embryo in Evaluating Disinfectants. ∗

Abstract

The recognition of the limited value of the phenol coefficient test in evaluating wound disinfectants has led to a search for methods by which the tissue toxicity as well as the germicidal action of those agents can be determined in vitro. While suggested methods 1 , 2 , 3 differ in detail, they all measure the toxicity of disinfectants for tissues and for the test bacteria. If the disinfectant is less toxic for tissue than for the test organisms, it is inferred that the disinfectant is therapeutically active. However, such an interpretation may not be entirely justified, since the problem of wound disinfection is highly complex and the factors that influence the process are diverse. This being the case, efforts should be continued to develop a reliable, easily reproducible and inexpensive method for determining the actual therapeutic value of disinfectants in vivo.

In this report, experiments are decribed indicating the utility of the infected chorioallantoic membrane of the developing chick embryo in studies on disinfectants. To illustrate the application of this method, results of testing the efficacy of aqueous solutions of phenol, iodine, and cetyl pyridinium chloride are presented.

Using the technic of Goodpasture and Buddingh, 4 windows were cut in the shells of eggs containing 11-day-old embryos, and a cover slip was placed over the opening of each. One the following day the chorioallantoic membranes were inoculated with 0.02 cc of a 1:10 dilution (about 1,500,000 organisms) of a 23-25 hr broth culture of Staphylococcus aureus (F.D.A. strain 209). Eighteen hours later and on each of the 5 days following, 0.2 cc of the test disinfectant was dropped on the membrane. On the day after the sixth treatment, the membrane was stroked with a moist cotton swab and with it half of a nutrient agar plate was streaked.