A us tra liaThe aim of this study was to evaluate the clinical use of a new culture system for the isolation of mycobacteria. Routine clinical specimens were cultured in the Mycobacteria Growth Indicator Tube, the radiometric Bactec 460 TB system and on Lowenstein Jensen (LJ) medium to compare recovery rates and times for detection of mycobacteria and contamination rates. MGIT was tested for its ability to support the growth of a wide range of mycobacterial species. Acid-fast bacilli (AFB) were detected on direct smears of 76 of 603 clinical specimens and mycobacteria were isolated by at least one method from 109 specimens; 93% of these were detected in the MGIT, 95% in the Bactec 460 TB system and 87% on L J medium. The MGIT, Bactec and L J media detected 92%, 97% and 95%, respectively, of 61 M. tuberculosis isolates and 94%, 94% and 77% of the 48 isolates belonging to the M. avium complex (MAC). The mean detection times in MGIT, Bactec and L J media for M. tuberculosis were 22, 14 and 27 days respectively, and for MAC were 14, 12, and 29 days, respectively. Growth of M. tuberculosis was detected in Bactec, within 4 weeks, in 93% of the 61 culture-positive specimens, compared with only 61% in MGIT and 66% on LJ. The number of MAC detected within 4 weeks was similar in Bactec and MGIT, but less in L J medium. Differences in sensitivity and time to detection of growth between media were greater for specimens in which AFB were not detected on direct smear than those on which AFB were seen. Contamination rates were similar in the three systems (3-4%). MGIT supported the growth of all 28 Mycobacterium spp. inoculated. MGIT has significant safety advantages and is less labour intensive than other methods, but the time to detection of M. tuberculosis, especially in smear-negative specimens, was longer in MGIT than in Bactec.

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SUMMARYGenetic relationships amongst 115 mainly Australian isolates of Mycobacterium avium were assessed using multilocus enzyme electrophoresis (MEE). The isolates were divided into 58 electrophoretic types (ETs), with a mean genetic diversity of 0-29. Isolates from humans were closely related to but distinct from those cultured from birds, whilst some porcine isolates belonged to the same ETs as certain human isolates. Pulsed field gel electrophoresis (PFGE) was used to differentiate related isolates, and those from birds and some from other animals, including pigs, were distinguished from the human isolates. The results of MEE and PFGE suggested that certain strains of M. avium may be transmitted between birds and pigs, but there was no clear evidence of transmission to humans. The serovar of the M. avium isolates was not obviously related to their ET assignment or their PFGE type.

SUMMARYThin-layer chromatography (TLC) was compared with seroagglutination for subtyping of Mycobacterium avium complex (MAC) bacteria. Seventy-five significant MAC isolates from patients with AIDS were typed by both methods and 36 isolates, judged to be clinically non-significant, were examined by TLC only. Overall, 75 % of isolates tested were typable by seroagglutination and 91 % by TLC; the results correlated between the two except for minor discrepancies.Serovars 1, 8 and 21 and mixed serovars 1-21 and 1-8-21 were common among isolates from AIDS patients and together represented 83 % of isolates compared wvith only 36% in the non-significant group (odds ratio 8-4; 95% confidence interval 3 4-23 3). This difference remained significant after exclusion of serovar 41 (M. scrofulaceum), which was the commonest isolate (28%) in the nonsignificant group but was not isolated from patients with AIDS.

Objective: To collate statistics, including drug susceptibility, of patients with bacteriologically confirmed tuberculosis in Australia during 1989–1992. Design: Collaborative project among the five Australian mycobacterial reference laboratories. Study population: 2509 Australian residents with bacteriologically confirmed tuberculosis. Outcome measures: Patient and specimen data, and drug susceptibility results recorded for isolates of Mycobacterium tuberculosis and Mycobacterium bovis. Results: The annual incidence during 1989–1992 was about 3.6 per 100000. The male‐to‐female ratio was 1.4:1 and about half the patients were under 50. Older men had high rates of disease. Lymphatic disease was significantly more common in females; the converse was true for pulmonary and pleural disease. Resistance to at least one of the common antituberculosis drugs was detected in 14.4% of isolates, and usually involved streptomycin (7.6%) and isoniazid (8.4%). Fewer than 1% of isolates were resistant to isoniazid and rifampicin in combination. Conclusions: By international standards, Australia remains a “low‐incidence” country for tuberculosis, with a static annual incidence. Multiple drug resistance is uncommon and most patients should respond to the standard four‐drug regimen. Nevertheless, because clinical data confirm that the pool of infected persons is being supplemented through immigration, and that certain population subgroups have high rates of disease, it is essential that Australia maintain effective control programs.