Gene Sequencing of Antibiotic-Resistant Bacteria Can Help Doctors Fight Back

The genetics of bacteria helps doctors know what treatment to use.

A scanning electron micrograph image of the MRSA bacteria. Image: CDC

Sequencing of the human genome might not pay off for most people for many years, but whole-genome sequencing of bacteria could start to play a huge role in healthcare. Researchers in the United Kingdom say that, by sequencing MRSA, a common, hard-to-treat skin infection, doctors can more easily find out how to kill it.

Every year, roughly 80,000 Americans get infected with MRSA, an antibiotic-resistant version of a staph infection, and incidence of the disease has more than doubled over the past five years. It is especially common in hospital settings and among dialysis patients. At any rate, the disease can often take weeks to treat as doctors shuffle through a series of antibiotics, any number of which a particular strain might be resistant to. 

By sequencing a patient’s particular strain, which costs just $70, doctors can quickly determine which antibiotics to use, which should greatly improve patient outcomes. Researcher Ruth Massey of the University of Bath found that there are more than 125 genetic mutations that can affect a particular strain of MRSA’s toxicity.

“From the genome, we can tell what antibiotics NOT to use and this paper shows us we can also see how likely to cause a severe infection the isolate is, and therefore how aggressively the patient should be treated,” Massey told me in an email. Massey published the results of her study in Genome Research.

Right now, the cost is already low enough to be clinically viable, but it still takes roughly three days to sequence a MRSA genome, so the speed will have to be improved if whole-genome sequencing is going to become routine. 

This isn’t the first time MRSA has been sequenced, but it is the most extensive: Massey looked at more than 90 different isolates of MRSA and found that certain ones were much more likely to cause illness, and that the mutations that caused higher toxicity existed throughout the genome. In 2012, researchers at the University of Cambridge used whole genome sequencing of the bacteria to help quell an outbreak in the United Kingdom.

In any case, genome sequencing is a new tool that doctors can use to find the weaknesses of particularly nasty strains of the bacteria.