A highly transmissible strain of superbug circulating in European hospitals has been found in the urban-dwelling hedgehogs of Helsinki, Finland. 

It’s not known whether the drug-resistant bacteria are a concern of the hedgehogs’ health, but it is apparent that urban wildlife needs to be closely monitored to limit the emergence of new antimicrobial resistance traits in the future.

The findings from the University of Helsinki were recently presented at the European Congress of Clinical Microbiology & Infectious Diseases in Portugal. 

Superbugs are pathogens that have grown resistant to antibiotics and other medications commonly used to treat the infections they cause. One of the best known is a group of bacteria known as methicillin-resistant Staphylococcus aureus (MRSA). Another common bacteria in humans, E. coli, can also gain drug resistance through developing ESBL enzymes that break down and destroy some commonly used antibiotics.

Once these bacteria infect humans, they can cause a range of conditions, including pneumonia, urinary tract infections, and skin infections, that are extremely troublesome to treat with the conventional selection of drugs. 

In this new study, researchers tested samples from 115 European hedgehogs (Erinaceus europaeus) from the Korkeasaari Zoo Wild Animal Hospital in Helsinki to discover that 10 percent were colonized by at least one MRSA-producing bacterial strain and 9 percent had at least one ESBL-producing strain 

They also found that four hedgehogs carried a specific strain, mecA-MRSA (t304/ST6), that has been tearing through hospitals in Northern Europe in recent years. 

“It is striking that we also found around 10 percent of hedgehogs were positive for ESBL-E-producing bacteria—double the prevalence in humans and companion animals in Finland (5 percent),” said Venla Johansson, study author and PhD student at the University of Helsinki. 

“Our findings could indicate a spillover of antimicrobial resistance from anthropogenic sources to urban wildlife, possibly creating secondary reservoirs in the environment from where clinically significant resistance may spread elsewhere.”

The overuse of antibiotics is one of the main drivers of antibiotic resistance in the modern world. However, strangely enough, hedgehogs were responsible for the emergence of the first MRSA superbugs long before the widespread clinical use of antibiotics. A study published earlier this year found that hedgehogs’ skin is home to a fungus that secretes antibiotics, causing the bacteria to have evolved antibiotic resistance in response. 

Back in Finland, it appears the hedgehogs picked up the infection from humans. The study found that two E. coli strains found in the hedgehogs, ST68 and ST69, are frequently the cause of serious bladder and bloodstream infections in people.

How exactly they acquired the infection remains unknown, but it’s likely it was picked up through a human source, such as waste or agricultural run-off that contained the bacteria with antibiotic-resistant genes. 

“All wildlife and livestock carry many different types of bacteria, so there are many candidates for its dispersal in urban environments including humans themselves. Moreover, anthropogenic sources, such as waste, agriculture runoff, and domestic wastewater have been linked to antimicrobial resistance transmission to wild animals,” said Johansson.