Bacteria study helps gauge infection risk

Bacteria may be able to jump between species with greater ease than was previously thought, a study suggests.

Researchers have found that a single genetic mutation in a strain of bacteria that infects humans enables it to also infect rabbits.

The discovery has major implications for how we assess the risks associated with bacterial diseases that can pass between people and animals.

Scientists at the universities of Glasgow and Edinburgh studied a strain of bacteria called staphylococcus aureus ST121, which is responsible for widespread epidemics in the global rabbit farming industry.

The team looked at the genetic make-up of ST121 to work out where the strain originated. They also tracked how changes in its genetic code enabled it to infect rabbits.

Host jump

They concluded that ST121 most likely evolved as the result of a host jump from humans to rabbits around 40 years ago.

A genetic mutation at a single site in the bacterial DNA code was sufficient to convert a human strain into one that could infect rabbits.

The discovery transforms our understanding of the minimal genetic changes that are required for bacteria to infect different species.

Domestication of animals, industrialisation of agriculture and globalisation have provided new opportunities for the transmission of bacteria between humans and animals. This latest research has important public and veterinary health implications which will require a re-examination of the future threat posed by bacterial host-switching events.

Skin infections

ST121 is found in the respiratory tract and on the skin of some people. While it is usually harmless, the bacteria can cause a variety of conditions from minor skin infections to meningitis and sepsis. In rabbits, the bacteria can cause serious skin infections.

Our results represent a paradigm shift in understanding of the minimal adaptations required for a bacterium to overcome species barriers and establish in new host populations.