Prevalence of antibodies to Legionella species in a series of patients in Israel.

A collection of serum specimens from 77 patients at various hospitals or clinics in Israel was used to determine the usefulness of the enzyme-linked immunosorbent assay (ELISA) with a multivalent antigen for the detection of legionella antibodies. Rickettsial infection rather than legionellosis was suspected in most of these patients. The multivalent antigen was derived from Legionella pneumophila serogroups 1-6, L. bozemanii WIGA, and L. micdadei TATLOCK. A preliminary test of the multivalent antigen with specific rabbit antisera had shown that homologous reactions were not appreciably reduced in strength or specificity by the presence of the heterologous antigens. The results with the human sera revealed that 28 patients (36%) had reciprocal dilution titers greater than or equal to 1,280 and 43 (56%) had titers greater than or equal to 320. Tests with univalent antigens identified L. bozemanii as the only or principal antigen reacting with 13 of these sera. In contrast to the sera reacting with other legionella antigens, the great majority (11 of 13) of L. bozemanii-positive sera reacted also with Rickettsia typhi. The data suggest that most, but not all, reactions with L. bozemanii were elicited by a cross-reacting R. typhi antigen. These results were confirmed by cross-absorption tests.