Background: The increasing incidence of tuberculosis caused by drug-resistant Mycobacterium tuberculosis is thought in part to reflect inadequate implementation of standard tuberculosis control measures. However, in San Francisco, USA, which has an effective tuberculosis control programme, we have recently observed an increase in cases of acquired drug-resistance.
Methods: To explore further this observation, we analysed the secular trend of acquired drug-resistance and conducted a population-based case-control study of all reported tuberculosis cases in the city of San Francisco between 1985 and 1994.
Findings: We identified 14 patients with tuberculosis caused by fully susceptible M tuberculosis who subsequently developed drug-resistance. Of these acquired drug-resistance cases, two occurred between 1985 and 1989, whereas 12 occurred between 1990 and 1994 (p = 0.028). In the case-control study, AIDS (odds ratio 20.2, 95% CI 1.12-363.6), non-compliance with therapy (19.7, 1.66-234.4), and gastrointestinal symptoms (11.5, 1.23-107.0) were independently associated with acquired drug-resistance. Between 1990 and 1994, one in 16 tuberculosis patients with AIDS and either gastrointestinal symptoms or non-compliance developed acquired drug- resistance.
Interpretation: The substantial increase in acquired drug- resistance in San Francisco seems to be a product of the increasing prevalence of HIV/M tuberculosis coinfection. Our data suggest that the interface of the HIV and tuberculosis epidemics fosters acquired drug-resistance, and that traditional tuberculosis control measures may not be sufficient in communities with high rates of HIV infection.