Drug resistance in Mycobacterium tuberculosis: a survey over 25 years in Blackburn.

Over the past 25 years the incidence of tuberculosis in Blackburn has changed from one that was below the national average to one which is consistently in the 10 highest local authority areas in England and Wales. A survey of primary and acquired drug resistance over the same period included 974 ethnic white patients and 538 of Indian subcontinent ethnic origin. Primary drug resistance in the white population has fallen consistently from 1965 onwards and is now zero. Only one case of acquired resistance has occurred in the last five years. Primary resistance in the immigrant community has been 11-15% from 1965 onwards, and five cases of acquired resistance have occurred since 1970. The pattern of drug resistance over this period supports the view that there is no evidence of cross infection between the native white and immigrant ethnic groups.