USE OF POLYMERASE CHAIN-REACTION IN AN EPIDEMIOLOGIC INVESTIGATION OFPONTIAC FEVER

In June 1992, 13 (38%) of 34 resort guests experienced illness that me t a symptom-based case definition of Pontiac fever. Each ill guest rep orted using an indoor hot tub compared with 6 (29%) of 21 nonill guest s (P < .001). Water samples from the indoor hot tub were culture-negat ive for legionellae using standard techniques, coculture with amebae, and intraperitoneal inoculation of guinea pigs. However, polymerase ch ain reaction (PCR) testing of the water samples indicated the presence of Legionella pneumophila. Direct fluorescent antibody testing identi fied the organism as serogroup 6. Seroconversion to L. pneumophila ser ogroup 6 occurred in 7 (64%) of 11 ill guests and none of 5 nonill gue sts (P = .03). These results suggest that in certain circumstances, cu lture of environmental samples should be supplemented with additional tests such as PCR. These results are also consistent with the concept that Pontiac fever can be caused by nonviable legionellae.