Experience with heat-killed antigens of L. longbeachae serogroups 1 and 2, and L. jordanis in the indirect fluorescence antibody test.

Sera from 1384 individuals were examined with a trivalent antigen composed of Legionella longbeachae serogroups 1 and 2 and L. jordanis. One hundred and twenty nine (9.3%) showed a reaction on screening. Thirty-six (2.6%) had a titre of greater than or equal to 64 with monovalent antigens. Ten (0.7%) had a high (greater than or equal to 256) or greater than or equal to fourfold rising titre of antibody to one or more antigens and six of these patients had a severe chest infection. No correlation was apparent between the presence of low level antibodies and disease.