Diagnosing multidrug resistant tuberculosis in Britain

Each year an estimated 8 million new cases of tuberculosis occur, leading to 3 million deaths; and almost a third of the world's population is infected by the causative bacterium, Mycobacterium tuberculosis. 1 2 The incidence of tuberculosis is rising in Britain too, and London has seen two recent outbreaks of multiple drug resistant tuberculosis—that is, resistance to at least isoniazid and rifampicin—in patients coinfected with HIV.3 This is one of several dramatic outbreaks of multidrug resistant tuberculosis described recently in Europe and the United States. Although overall the problem of resistance remains small in the UK, lessons from recent cases can help clinicians suspect multidrug resistant tuberculosis and enable their laboratory colleagues to identify it quickly. Updated guidelines on the management of cases of tuberculosis have recently been published.4 The UK drug resistance surveillance system MYCOBNET, coordinated by the Public Health Laboratory Service, shows that levels of multidrug resistant tuberculosis in the UK are relatively low but the incidence is higher in London than elsewhere. In 1993-6 rates of multidrug resistant tuberculosis in initial isolates rose from 0.6% to 1.7% overall; in 1993-6 1.9% of isolates from greater London were multidrug resistant compared with 0.9% outside the capital.5 As shown …