Tuberculosis among urban health care workers: a study using restriction fragment length polymorphism typing.

Cases of tuberculosis identified during 1992-1994 through an active tuberculosis surveillance network among six hospitals that serve New York City (the TBNetwork) were analyzed according to the occupational status of the patients. Clinical data were obtained by review of medical records, and restriction fragment length polymorphism (RFLP) typing of Mycobacterium tuberculosis isolates was performed. No known nosocomial outbreaks of tuberculosis occurred at these hospitals in the study period. Occupational status was known for 142 of 201 patients whose isolates were available for strain typing. Patients infected by organisms with a clustered strain typing pattern, as determined by RFLP analysis, were presumed to have recently acquired disease. RFLP typing revealed that isolates from 13 (65%) of 20 health care workers and 50 (41%) of 122 non-health care workers had a clustered RFLP pattern. The strains infecting eight (89%) of nine health care workers seropositive for human immunodeficiency virus (HIV) had a clustered RFLP pattern. Multivariate analysis of 75 patients with known HIV and occupational status revealed that HIV status (P = .03) and health care worker status (P = .02; RR = 2.77) were independent risk factors for a clustered RFLP strain. These findings suggest that many of the apparently sporadic cases of tuberculosis among health care workers may be due to unrecognized occupational transmission.

Transmission of multidrug-resistant tuberculosis in a large urban setting.

Multidrug resistance has become an increasingly important problem in the control and prevention of tuberculosis in large urban centers. Although several small outbreaks of multidrug-resistant (MDR) tuberculosis in New York City have been reported, the increase in the number of cases is not fully explained by these recognized outbreaks, and the modes of transmission have not been clearly delineated. Transmission patterns of MDR tuberculosis in New York City, therefore, were studied by stratifying Mycobacterium tuberculosis isolates from 167 newly diagnosed tuberculosis patients according to their DNA restriction fragment length polymorphisms (RFLP). Forty-three (34%) of 127 drug-susceptible isolates and 19 (79%) of 24 multidrug-resistant isolates had RFLP patterns representing possible recent exogenous infection (primary tuberculosis). Patients who had such isolates were more likely to be seropositive for human immunodeficiency virus (58%; p < 0.05), non-Hispanic black (56%; p < 0.005), U.S.-born (57%; p < 0.001), and have MDR tuberculosis (79%; p < 0.0005). In a logistic regression model, primary tuberculosis remained significantly associated with MDR tuberculosis and black race. In contrast to previous reports, in New York City recent exogenous transmission accounts for most new cases of multidrug-resistant tuberculosis.