Identification of Listerella monocytogenes . ∗

Abstract

That Listerella monocytogenes may cause a severe experimental conjunctivitis in several animal species was pointed out in an earlier report. 1 While, as will be seen, the ocular infection is both a curious and characteristic reaction, it was not particularly emphasized at the time as a potential diagnostic test, since the study was made with only 2 strains. Since that communication, however, the isolation of this organism from the blood of a patient with infectious mononucleosis furnished the initiative for determining the possible accuracy of the conjunctival reaction in the identification of Listerella monocytogenes. While other procedures, such as the stimulation of mononucleosis in susceptible animals, agglutination in specific anti-sera, and fermentative reactions, are also helpful for the purpose, the test to be suggested is much more readily accomplished, requires little preparation, and eliminates entirely the question of interpretation, so that it is recommended as a method of simple and accurate diagnosis. Eight strains have been collected from various animal and human sources, and all have been found to give typical reactions, so it is felt that the test may be of actual value. While the number of cultures studied is small, it must be remembered that the total number of strains of Listerella monocytogenes available at the present time is not much more than twice as great.

In conducting the test, young cultures (18–24 hours) are applied either by instillation of heavy suspensions into the conjunctival sac or by swabbing the everted conjunctiva. This may be done by running a moistened swab over the surface of a blood-agar culture and then transferring the organisms by light massage to the conjunctiva of the animal to be tested. While the reaction has been reproduced with equal readiness in the rabbit, guinea pig, and rat, it has been found more convenient to employ the rabbit.