Tuberculosis in Australia: bacteriologically confirmed cases and drug resistance, 2005.

The Australian Mycobacterium Reference Laboratory Network (AMRLN) collects and analyses laboratory data on new cases of disease caused by the Mycobacterium tuberculosis complex. In 2005, a total of 810 cases were identified by bacteriology; an annual reporting rate of 4.0 cases per 100,000 population. Isolates were identified as M. tuberculosis (n = 806), Mycobacterium africanum (n = 2) and Mycobacterium bovis (n = 2). Fifteen children aged under 10 years had bacteriologically-confirmed tuberculosis. Results of in vitro drug susceptibility testing were available for all 810 isolates for isoniazid (H), rifampicin (R), ethambutol (E), and pyrazinamide (Z). A total of 74 (9.1%) isolates of M. tuberculosis were resistant to at least one of these anti-tuberculosis agents. Resistance to at least H and R (defined as multi-drug resistance, MDR) was detected in 12 (1.5%) isolates; nine were from the respiratory tract (sputum n = 8, bronchoscopy n = 1). Of the 74 M. tuberculosis isolates resistant to at least one of the standard drugs, 67 (90.5%) were from new cases, 6 from previously treated cases, and no information was available on the remaining case. Eight were Australian-born, 65 were overseas-born, and the country of birth of one was unknown. Of the 65 overseas-born persons with drug resistant disease, 41 (63.1%) were from 4 countries; Vietnam (n = 16), Papua New Guinea (n = 10), the Philippines (n = 9), and India (n = 6). A retrospective review of AMRLN data on isolates collected between 2000 and 2005 found that none of 70 MDR-TB isolates met the new definition for extensively drug resistant TB (XDR-TB, i.e. MDR-TB with additional resistance to quinolones and second-line injectable agents).