ANTIBODIES TO BARTONELLA SPECIES IN INNER-CITY INTRAVENOUS-DRUG-USERSIN BALTIMORE, MD

Background: Bartonella quintana has recently been associated with home less alcoholic men. Both B quintana and Bartonella henselae have been shown to be opportunistic pathogens of people with acquired immunodefi ciency syndrome. The reservoirs and modes of transmission of these inf ections are incompletely known. Objectives: To examine serum samples t hat were taken from inner-city intravenous (IV) drug users for antibod ies to Bartonella organisms to determine whether there is an urban tra nsmission cycle for Bartonella species and to examine the demographic and behavioral characteristics of IV drug users to identify possible r isk factors for infection with any of these agents. Materials and Meth ods: A serologic survey was conducted, using a convenience sample of s erum specimens collected during a study of IV drug use and human immun odeficiency virus infection among 630 inner-city residents in Baltimor e, Md. A detailed questionnaire was administered at the initial collec tion of serum, and additional serum collections and questionnaire upda tes were made at 6-month intervals. The most recent available serum sa mple was tested for Bartonella antibody titer by using the indirect im munofluorescent antibody test with 3 antigens: Bartonella elizabethae, B henselae, and B quintana. Univariate and multivariate analyses of s elected potential demographic and behavioral risk factors were conduct ed. Results: Antibodies to Bartonella were highly prevalent in this gr oup; more than 37% of all samples reacted with at least 1 antigen. Ove rall seroprevalence of antibodies to B elizabethae, B henselae, and B quintana was 33%, 11%, and 10%, respectively. Current IV drug use, fre quency of injection, and seronegative human immunodeficiency virus sta tus were significantly associated with Bartonella antibody presence, b ut these associations varied by analysis. There was a significant inve rse association of antibody prevalence to B henselae and B quintana by using CD4(+) cell counts among human immunodeficiency virus-seroposit ive individuals. Conclusions: Intravenous drug users have an elevated prevalence of antibodies to Bartonella organisms and may be at signifi cant risk of becoming infected. Current IV drug use, high frequency of injection, and seronegative human immunodeficiency virus status are s ignificant risk factors for an increased prevalence of Bartonella anti bodies. The current natural histories of Bartonella species are rapidl y changing, and mechanisms of transmission remain unknown.