FALSE-POSITIVE LEGIONELLA SEROLOGY IN CAMPYLOBACTER INFECTION - CAMPYLOBACTER SEROTYPES, DURATION OF ANTIBODY-RESPONSE AND ELIMINATION OF CROSS-REACTIONS IN THE INDIRECT FLUORESCENT-ANTIBODY TEST

Sera from 83 patients with campylobacter gastroenteritis were examined for the presence of legionella antibodies by indirect immunofluoresce nce. Twenty-one patients (25%) had positive titres (greater than or eq ual to 16) including 11. patients with titres of greater than or equal to 128. Legionella seropositivity persisted in 5 of 9 patients (55 %) studied for 6-9 months. Campylobacter isolates were serotyped by the Penner scheme. Isolates associated with legionella seropositivity incl uded Penner types 1, 2 and 4, the common endemic serotypes in England, Campylobacter blocking fluids were prepared from a range of Penner re ference strains. The blocking fluid prepared from Penner type 11 was t he most efficient at inhibiting the false-positive legionella titres. Using this absorption step legionella titres were inhibited from 24 of 26 patients (92 %) with campylobacter but not from 8 patients with cu lture-proven legionnaires' disease. We recommend that this method is i ncorporated into routine diagnostic legionella serology in order to el iminate false-positive reactions due to campylobacter.