SEROPREVALENCE TO BARTONELLA-QUINTANA AMONG PATIENTS AT A COMMUNITY CLINIC IN DOWNTOWN SEATTLE

In 1993, an outbreak of 10 cases of Bartonella quintana bacteremia occ urred among homeless, alcoholic, human immunodeficiency virus (HIV)-ne gative persons in Seattle. To estimate the prevalence of past exposure B. quintana among this population, a serosurvey was conducted in 1994 among patients at a downtown Seattle clinic. Microimmunofluorescent t iters to B. quintana in 192 clinic patients were compared with titers in 199 age- and sex-matched Seattle volunteer blood donors, Titers gre ater than or equal to 64 were detected in 20% (39/192) of clinic patie nts compared with 2% (41/99) of blood donors (P < .001). Among clinic patients, alcohol abuse was independently associated in multivariate a nalysis with titers greater than or equal to 64 (odds ratio, 3.3; 95% confidence interval, 1.6-6.9). Of the 39 patients with B. quintana tit ers greater than or equal to 64, 24 (62%) also had titers greater than or equal to 64 to Bartonella henselae, indicating serologic cross-rea ctivity between Bartonella species. These results suggest that a subst antial proportion of this indigent, inner-city Seattle population was infected with B. quintana.