Tuberculosis in Australia: bacteriologically confirmed cases and drug resistance, 1996. Report of the Australian Mycobacterium Reference Laboratory Network.

The Australian Mycobacterium Reference Laboratory Network collected and analysed laboratory data on new diagnoses of infection with Mycobacterium tuberculosis complex during 1996. A total of 750 cases were identified, representing an annual incidence of 4.1 cases of laboratory confirmed tuberculosis per 100,000 population. The incidence rate varied between States, reflecting differences in the distribution of persons belonging to 'high-risk' categories for tuberculosis. Incidence statistics were almost identical to those recorded by the Network in 1994 and 1995. The male:female ratio remained at around 1.2:1. As was the case in 1995, the median age group for males was 45-49 years and for females 35-39 years. The frequency of positive microscopy in pulmonary samples was stable at around 55%. Lymphatic disease accounted for 19% of the total cases in 1996 compared with 15% in the previous year, confirming that lymphadenitis is becoming more common in females with tuberculosis in Australia. Approximately 11% of isolates had in vitro resistance to at least one of the four standard anti-tuberculosis drugs, an increase from 8% in 1994-95. Fifteen isolates were multi-drug resistant, compared with a total of only 38 during the previous seven years. Thus, the 1996 data points to an increasing frequency of multi-drug resistant strains among isolates from Australian patients with tuberculosis.