Resident gut bacteria can cause disease if the balance of gut microflora is disrupted, for example, by antibiotics. Researchers at the University of California, Berkeley, show that a strain of gut Escherichia coli can cause sepsis in antibiotic-treated mice by triggering excessive inflammation.

Janelle Ayres and her colleagues gave mice a cocktail of antibiotics and a gut-injuring chemical. The animals soon showed hypothermia and multiple organ damage — signs of sepsis. A strain of antibiotic-resistant E. coli isolated from these mice caused disease when injected into normal animals.

This E. coli strain seems to cause sepsis by activating protein complexes called inflammasomes, which can stimulate excessive inflammation in the presence of pathogens.

Nature Med. http://dx.doi.org/10.1038/nm.2729 (2012)