Effect of Intravenous Bacterial Filtrates on Skin Tests and Local Infections.

Abstract

In a previous report 1 we have shown that rabbits are often naturally allergic to filtrates of many gram negative bacteria. It was suggested that this allergy is due to the overwhelming predominance of gram negative organisms in the upper respiratory tract of these animals and to the fact that chronic infections are quite common in this region. Positive skin tests are given not only to broth filtrates of B. lepisepticum and other bacteria representing the normal nasopharyngeal flora, but to the other organisms such as B. coli, B. influenzae and even to such an organism as meningococcus, to which the animal has never been directly exposed. Rabbits lacking this natural allergy develop it about one week after infecting the skin with a virulent strain of B. lepisepticum. In fatal infections, skin allergy does not appear. When large necrotic lesions develop, a positive skin test may not be elicited until the 15th day or later, but before healing begins, it becomes quite striking and is of valuable prognostic import. The intensity of reaction usually recedes with the clearing up of the infection and the development of a generalized immunity. During this phase of acquired allergy, the animal reacts non-specifically to the filtrates of many gram negative organisms of widely different groups.

When filtrates of strains of B. lepisepticum and other gram negatives are injected intravenously, the reaction is quite different in the allergic and non-allergic rabbit. The highly sensitized animal often develops diarrhea about 20 minutes after the injection. He rapidly goes into shock and dies in convulsions within a few hours, even when one cc. or less of the filtrate is used; while the non-allergic animal usually will survive 15 cc. or more without marked symptoms. Filtrates from highly virulent strains of B. lepisepticum occasionally will kill a non-allergic rabbit. Rabbits completely recovered from a severe B. lepisepticum infection and with skin reactions still moderately strong, show no ill effects from very large doses of the filtrate. The striking lesion in animals dying from filtrate injections is marked congestion of the lungs and bronchi with hemorrhage. Occasionally there are hemorrhages in the skin and other organs.