A common genetic difference between people influences their chance of developing a rare but serious liver injury as a side effect of taking the antibiotic flucloxacillin, as reported in a paper published online in this week's issue of Nature Genetics.

Flucloxacillin is widely used in Europe and Australia to treat staphylococcus bacterial infections. In their study, Daly and colleagues found that individuals carrying the risk-associated gene variant were 80-100 times more likely than non-carriers to suffer liver injury in response to this antibiotic.

The risk-associated gene variant is relatively common in Northern Europe, but less prevalent in Africa and Asia. Despite being at substantially higher risk than non-carriers, only a small proportion of carriers actually develop liver problems in response to flucloxacillin. Thus, further tests will be needed to determine whether a genetic test would be clinically useful in guiding treatment options.