Oral Presentation Australian Society for Microbiology Annual Scientific Meeting 2017

Mapping the origin and spread of Mycobacterium tuberculosis complex in the Tasmanian population using whole-genome sequence and epidemiological data analyses (#171)

Ronan F O'Toole 1 , Micheál Mac Aogáin 2 , Louise A Cooley 3 , Greg Haug 4 , Maria Globan 5 , Janet A Fyfe 5 , Sanjay S Gautam 1
  1. School of Medicine, University of Tasmania, Hobart, Tasmania, Australia
  2. Department of Clinical Microbiology, Trinity College Dublin, Dublin, Ireland
  3. Department of Microbiology and Infectious Diseases, Royal Hobart Hospital, Hobart, Tasmania, Australia
  4. Launceston General Hospital, Launceston, Tasmania, Australia
  5. Victoria Infectious Diseases Reference Laboratory, Peter Doherty Institute, Melbourne, Victoria, Australia

 

Background

Tuberculosis (TB) in Tasmania peaked at 248 cases in 1940 but has since declined in prevalence. Today, Tasmania has an annual incidence rate of 1.8 per 100,000 persons compared to 5.8 per 100,000 nationally in 2014. There are a number of interesting factors regarding TB in the state. Firstly, TB in Tasmania had been considered to consist of isolated cases imported from other jurisdictions. Secondly, it was believed to be free of multi-drug resistant forms of the disease.

 

Experimental Approach

In this work, we performed whole-genome sequencing of cultured isolates of Mycobacterium tuberculosis complex from 2014-2016 and correlated with clinical and public health surveillance data to better understand the epidemiology of TB in Tasmania.

 

Results

We examined two probable clusters of the disease during the above time period. One of the clusters occurred from May to August 2015 in individuals (n=4) from Nepal. The second cluster occurred between November and December 2014 in individuals (n=2) from New Zealand. Our single-locus variant analysis has established that the isolates within each are identical and therefore, constitute confirmed TB clusters. Here we also report the first known case of MDR-TB in Tasmania, which emerged in 2016. We extracted evidence on the resistance and origin of the isolate from its genome sequence. In addition, we examined a case of pulmonary TB in a Tasmanian-born individual in 2014 due to Mycobacterium bovis. We discuss how it may have appeared post the eradication of bovine TB from cattle herds in Tasmania in 1975 under the Brucellosis and Tuberculosis Eradication Campaign in Australia.

 

Conclusions

Tasmania exhibits features of TB observed in other jurisdictions, namely clustering of cases and the emergence of drug resistance. Hence, the state is not immune to major risks associated with TB globally. Early detection of TB and contact tracing, coordinated with rapid laboratory diagnosis, drug-susceptibility testing and molecular typing, are essential for effective control of the spread of TB in Tasmania.