• Question: Are there different strains of TB? If so, do they have different sugars?

    Asked by missc to Enda, Jean, Kate, Kev, Tim on 19 Nov 2012.
    • Photo: Jean Bourke

      Jean Bourke answered on 19 Nov 2012:

      There are many many different strains of TB. Strains can be grouped into families that have a common ancestor. They have certain things in common but yes there are certain things to mark out different strains and they include the sugars on the outside of the bacteria.

      A lot of the time we do know why these sugars are there and what their purpose is. This is what I’m working on.

    • Photo: Tim Downing

      Tim Downing answered on 19 Nov 2012:

      Hi Missc,

      Yes by having many strains and lots of variation, TB kills 1.5+ million annually. The WHO estimate for 2008 was ~1.9 million, 15% of which were spread by person-person contact. 1 out of every 3 cases of TB are opportunistic – ie the people already had an infection, and then TB jumped in while their defences were low. So this is why it is not usually transmitted between people: most of us are exposed to it, but we do not get sick but our immune systems are healthy and strong.

      However, epidemics do occur. These tend to be of one strain only – for example in 2011 there was an epidemic in Canada where all the TB infections looked very similar at the level of DNA. For instances like this, examining other difference – eg sugars and proteins can be more useful as indicators of why the outbreak has happened. Because bacteria like TB also have some different sugars/proteins compared to us, then examining them can help track their movement in our bodies.

      Tim

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