CBTBR identifies mixed TB infections

NOVEMBER 2005

In the American Journal for Critical Care and Respiratory Medicine, researchers at the US node showed a novel mechanism whereby patients may develop drug-resistant tuberculosis. In the past, drug-resistant tuberculosis was largely ascribed to the transmission of drug-resistant strains or acquisition of drug-resistance through poor adherence.  In this study a new method was developed to elucidate the finer details of the population structure of M. tuberculosis strains in sputum cultures. Using this methodology, the researchers showed that a significant number of patients may be infected simultaneously with both a drug susceptible and drug-resistant strain. However, the drug-resistant strain is not detectable by classical mycobacteriological methods. Thus, during standard antibiotic treatment there is a selection for the resistant strain and the patient subsequently presents with drug-resistant tuberculosis. In such cases there is a risk that the drug-resistant strain may be transmitted to close and causal contacts thereby perpetuating the drug-resistant epidemic. This highlights the need for the development of more sensitive diagnostics for the detection of underlying drug-resistance. The fact that an individual may present with multiple infections demonstrates the severity of the tuberculosis epidemic and the need to rapidly identify infectious source cases before transmission occurs. 

CBTBR’s drug resistant M.tb genome sequence a world first

NOVEMBER 2005

The problems and threats associated with drug resistant Mycobacterium tuberculosis  increase the TB burden on the community and call for specialised diagnostics and treatment. Solutions to this growing problem are based on a firm understanding of the genetic composition of these resistant strains. In September this year, the CBTBR made world news by the release of the genome sequence of a drug-resistant F11 M.tb isolate.  The sequencing of the F11 strain is the product of a collaboration including the CBTBR, the Harvard School of Public Health and the Microbial Sequencing Centre of the Broad Institute. The F11 strain family has been identified as a major role player in the TB drug resistance associated with the Western Cape (more than 20% of reported drug resistant strains) and the release of the full genome sequence will assist researchers in the understanding of the mechanisms that makes this strain so successful in escaping the anti-tuberculosis treatment.What makes this achievement more significant is that it is not just the first drug-resistant TB strain that is sequenced, but also the first from the African continent. The CBTBR and its collaborators are hoping to sequence another seven M.tb strains. For more information click here.