We studied the serological cross-reactions among Bartonella henselae, Chiamydia pneumoniae and Coxiella burnetii by indirect fluorescence antibody (IFA) method, using sera from 8 patients with cat scratch disease (CSD), 13 patients with C. pneumoniae infection and 12 patients with acute Q fever.
B. henselae IgG antibody was negative in 13 patients with C. pneumoniae infection, and was positive in 3 (titers being 1: 64) of 12 patients with Q fever, whereas B. henselae IgM antibody was negative in all the patients with C. pneumoniae infection or Q fever. C. burnetii IgG antibody was removed by absorption of these 3 sera with C. burnetii antigens, whereas B. henselae IgG antibody did not change. C. pneumoniae IgG antibody was positive in 3 (titers being 1: 125 in two, 1: 32 in one) of 8 patients with CSD. Both C. pneumoniae and B. henselae IgG antibody titers were significantly reduced by absorption of these 3 sera with B. henselae antigens. C. burnetii IgG or IgM antibodies were negative in all patients with CSD.
In conclusion, no serological cross-reaction between B. henselae and C. burnetii was observed. On the other hand, B. henselae IgG antibody cross-reacted to C. pneumoniae antigens, whereas C. pneumoniaeIgG antibody did not cross-react to B. henselae antigens. Our findings suggest that determination of B. henselae IgG or IgM antibodies were not influenced by C. pneumoniae and C. burnetii antigens.