Agar gel precipitin analyses in laboratory-acquired tularemia.

Serologic analyses reported in the past of patients with laboratory-acquired (1) and naturally acquired (2-4) tularemia have revealed, at the onset of most of the laboratory-acquired infections, moderate to low agglutinin titers as a result of prior immunization. A diagnostic fourfold rise in titer usually did not take place until the third to fourth week of disease, with maximal responses during the second to third month. Agglutinins frequently persisted for years at levels somewhat below this maximum. In some patients a diagnostic rise in hemagglutinins was demonstrated a week earlier than with agglutinins (1). No importance has been attached to the presence of agglutinins or hemagglutinins as regards protection from infection, nor has the presence or absence of these antibodies offered an understanding of the clinical problems of relapse and reinfection (5-8). The application of other techniques seemed indicated in a search for serologic tests that would detect a diagnostic change sooner and that would offer some immunologic explanation of relapse and reinfection. The present communication reports serologic measurements, including those obtained with the agar gel diffusion technique, on the sera of 29 patients with laboratory-acquired tularemia. Included in this group are five patients who experienced a clinical relapse in their disease and one who became reinfected. The 29 patients reported here represent proved cases of laboratory-acquired tularemia and are from the group reported by Overholt and colleagues (8). All but one subject had received prior immunization of a varying degree with the Foshay vaccine. Pulmonic or typhoidal tularemia occurred in 26 patients, and the other 3 had ulceroglandular disease. About one-half of the group was moderately to severely ill. Twenty-seven patients were * Published in abstract form, Clin. treated with tetracycline, 2 g daily in divided doses, and two patients, in addition to tetracycline, received strepto-mycin, 1 g daily in divided doses. The variations in the duration of therapy are seen in Figure 4. Five patients experienced a relapse in disease from 4 to 13 days after therapy was discontinued. One of the patients represents a case of proved reinfection with tularemia. Skin tests were performed intradermally with 0.1 ml of a 1:1,000 dilution in physiological saline of the standard phenolized vaccine on the flexor surface of the forearm. The test was considered positive if 10 mm or more of erythema or edema was present at 48 hours. Baseline sera were available from the 3 months prior to the …