New study from the Roslin Institute shows how easy it can be for bacteria to jump species

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

In a collaboration between the Universities of Edinburgh and Glasgow, researchers have found that a single genetic mutation in a strain of bacteria that infects humans enables it to also infect rabbits.

(L:  British wild rabbit; R:  Colour scanning electron micrograph of Staphylociccus aureus; Images courtesy of Wikimedia Commons)

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

Rabbit disease

The team, including members of the Centre for Immunity, Infection and Evolution and the Roslin Institute at the University of Edinburgh, studied a strain of bacteria called Staphylococcus aureus ST121.  This strain is responsible for widespread epidemics in the global rabbit farming industry.  ST121 is also 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.

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.

A single nucleotide change is enough

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.

Professor Ross Fitzgerald, from the Roslin Institute at the University of Edinburgh, who co-lead the study said

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.

Professor Jose Penades, Institute of Infection, Immunity and Inflammation, University of Glasgow, also commented that

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.

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