Investigation of Cross-Reactions With Francisella Tularensis Antibodies To Brucella

Abstract

Objective: Cross-reactions with Francisella tularensis antibodies to Brucella, Legionella, Yersinia, and Mycoplasma species have been described. F.tularensis LPS is able to induce serological crossreactions indistinguishable from brucellosis due to a similar immunodominant epitope in the Brucella O-polysaccharide. In agglutination tests, cross-reaction occurred only between F.tularensis and Brucella abortus, cross reactivity with Brucella can confuse interpretation of the results. Method: The aim of this study was to assess cross reactions and whether IgM or IgG antibodies are responsible for Brucella and F.tularensis crossreactions, by the use of microagglutination, Brucella ELISA and 2-mercaptoethanol microagglutination test. Results: Cross-reaction agglutinin titers to B.abortus antigen were found in 49 of 260 (18.8%) tularemia positive serum specimens, and cross-reaction titers to F.tularensis antigen were found in 23 of 252 (9.1%) Brucella positive serum specimens. While thirty six (73.5%) tularemia positive serum titers had Brucella cross reactivity at the titers of 1:20-1:80, cross-reaction with =1:160 titers was found in 13 samples (26.5%). The cross-reaction titers to B.abortus antigen were reduced to equal or less 1:40 titers by 2-ME. Cross- reactivity at the titers of 1:20-1:80 was determined in 22 of 23 Brucella positive samples. Conclusion: The cross-reaction titers determined with MA test in both infections were reduced to 40 or less by 2-ME, suggesting that the titers are due to immunoglobulin M antibody.