A notorious superbug that causes hospital-acquired infections has lately been spreading from pets to humans, Chinese scientists warn in a new study.

The bacterium Acinetobacter baumannii is one of the pathogens labelled “Priority 1” by the World Health Organisation, meaning it poses the greatest threat to human health and has developed a high level of resistance to antibiotics.

It causes conditions like meningitis and pneumonia in humans, and has been shown to cause similar symptoms – such as pneumonia, respiratory and urinary tract infections – in pet dogs, cats, and horses.

Animals that are known to suffer from A. baumannii infections include horses, cats,dogs, sheep, minks, and falcons.

Now, scientists have assessed which varieties of this bacterium infecting animals pose the most danger to humans.

In the study, researchers assessed genetic data on over 500 A. baumannii samples collected from animals in 17 countries, spanning 33 species, including white storks from Poland, as well as cats, dogs, and horses in veterinary clinics across Europe.

They also analysed samples of the bacterium from humans across the same regions.

Scientists found that A. baumannii from animals can be divided into two groups of varying risk to humans.

One is a low-risk group dominated by hosts such as livestock, poultry, and wildlife.

But there is also a high antimicrobial resistance (AMR) group dominated by hosts such as horses, cats, and dogs, the study warns.

The variant of the superbug from cats, dogs, and horses is genetically almost indistinguishable from those infecting people in hospitals nearby, researchers found.

Genome similarity between strains in humans and pets was almost 99 per cent, and in some cases even over 99.5 percent, they said.

"Our study suggests that A. baumannii has a higher potential of intertransmission between companion animals and humans compared to livestock, poultry, and wildlife," scientists wrote in the study published in the journal Applied and Environmental Microbiology.

"This elevated potential may be related to the close contact of companion animals with humans,” they wrote.

Strains of the superbug in pets carried two genes that make it resistant to carbapenem antibiotics, which are the last-resort drugs that doctors reach for when nothing else works.

Scientists hope to conduct more species-specific sampling of pathogenic bacteria to better understand the risk posed by superbugs from pets and other companion animals.