TRANSMISSION OF TUBERCULOSIS IN NEW-YORK-CITY - AN ANALYSIS BY DNA-FINGERPRINTING AND CONVENTIONAL EPIDEMIOLOGIC METHODS

Background. The incidence of tuberculosis and drug resistance is incre asing in the United States, but it is not clear how much of the increa se is due to reactivation of latent infection and how much to recent t ransmission. Methods. We performed DNA fingerprinting using restrictio n-fragment-length polymorphism (RFLP) analysis of at least one isolate from every patient with confirmed tuberculosis at a major hospital in the Bronx, New York, from December 1, 1989, through December 31, 1992 . Medical records and census-tract data were reviewed for relevant cli nical, social, and demographic data. Results. Of 130 patients with tub erculosis, 104 adults (80 percent) had complete medical records and is olates whose DNA fingerprints could be evaluated. Isolates from 65 pat ients (62.5 percent) had unique RFLP patterns, whereas isolates from 3 9 patients (37.5 percent) had RFLP patterns that were identical to tho se of an isolate from at least 1 other study patient; the isolates in the latter group were classified into 12 clusters. Patients whose isol ates were included in one of the clusters were inferred to have recent ly transmitted disease. Independent risk factors for having a clustere d isolate included seropositivity for the human immunodeficiency virus (HIV) (odds ratio for Hispanic patients, 4.31; P = 0.02; for non-Hisp anic patients, 3.12; P = 0.07), Hispanic ethnicity combined with HIV s eronegativity (odds ratio, 5.13; P = 0.05), infection with drug-resist ant tuberculosis (odds ratio, 4.52; P = 0.005), and younger age (odds ratio, 1.59; P = 0.02). Residence in sections of the Bronx with a medi an household income below $20,000 was also associated with having a cl ustered isolate (odds ratio, 3.22; P = 0.04). Conclusions. In the inne r-city community we studied, recently transmitted tuberculosis account s for approximately 40 percent of the incident cases and almost two th irds of drug-resistant cases. Recent transmission of tuberculosis, and not only reactivation of latent disease, contributes substantially to the increase in tuberculosis.