Messing with my flora (Image: Alain Pol/ISM/SPL)

ANTIBIOTICS can cause long-lasting changes in the bacteria living in the human gut. As changes in gut flora could increase the risk of some chronic diseases, such as inflammatory bowel syndrome, each course of antibiotics may represent a trade-off between short-term benefit and long-term risk.

Les Dethlefsen and David Relman of Stanford University in California collected more than 50 stool samples from three people over a 10-month period that included two courses of the antibiotic ciprofloxacin. They used gene sequencing to identify the microbial strains present in each sample. They found that …