Evolution in Action

Natural selection in antibiotic resistant bacteria.

As the cost of sequencing goes down, a lot of once-crazy experiments become feasible. There’s a good case in point this week in the preprint section of PNAS. A team of researchers looked at a single patient undergoing treatment with vancomycin for a serious infection. (Just saying “vancomycin” makes the “serious infection” part redundant, since it’s often the last resort). They periodically isolated Staphylococcus aureus bacteria from the patient’s blood during the course of the treatment to look at how resistance to the antibiotic developed.

Fine, fine – except the way they watched the process was to sequence the whole genome of each bacterial isolate. What they found were a total of 35 mutations, which developed sequentially as the treatment continued (and the levels of resistance rose). Here’s natural selection, operating in real time, under the strongest magnifying glass available. And it’s in the service of a potentially serious problem, since resistant bacteria are no joke. (Reading between the lines of the PNAS abstract, for example, it appears that the patient involved in this study may well not have survived).

(via Reddit)