The Nature sub-journal breaks the conventional wisdom: superbugs in the environment rarely transmit to humans

An international team of scientists investigating the spread of a deadly drug-resistant bacterium comparable to MRSA found that although the bacteria are found in livestock, pets and the wider environment, they are rarely transmitted to humans
through this route.

The researchers, led by Professor Ed Feil from the Massachusetts Institute of Technology in the United States, investigated Klebsiella, a harmless bacterium that lives in the gut but poses a danger
if it spreads to other parts of the body.

Klebsiella pneumoniae is the most well-known of this family and can cause pneumonia, meningitis, urinary tract infections, and bloodstream infections
.

These bacteria are now highly resistant to antibiotics, and some strains are even resistant to carbapenem antibiotics, one of the so-called "last resort" classes of antibiotics that are only used
when other antibiotic treatments are ineffective.

Klebsiella has surpassed MRSA as a health problem in the UK, and its incidence is steadily increasing
.
WHO has identified the bacterium as a key priority care-associated pathogen
.

In addition to being found in hospitals, the microbe has previously been detected in the environment, including livestock and wastewater, but until now it was unclear whether the bacterium spread
between clinical and non-clinical settings.

In the largest study conducted to date, the team collected 6,548 samples over a 15-month period from different locations in and around the Italian city of Pavia, a pathogen that was a major problem in hospitals in the city of Pavia, and analyzed them using whole genome sequencing technology to detect and identify any pathogen Klebsiella bacteria present
.

The team wiped down patients at hospitals and health "carriers" in the community with cotton balls, taking samples from farms, puddles, livestock and even houseflies and other insects to detect where
the bacteria were present.

From this, they found 3482 isolates, including 15 different species containing half of the positive samples for Klebsiella
.

When the team genetically sequenced the bacteria to find the strains present, they found little overlap
between the bacteria found in hospitals and those found in the environment.

Professor Ed Phil, who led the study, said: "Klebsiella infections are becoming increasingly resistant to antibiotics, so in the past you could easily treat most urinary tract infections, now it is more common for patients to have infections that keep coming back, causing problems
.

"Klebsiella can also cause pneumonia, which causes about half of all patients to die
.
These bacteria are a bigger problem
in the UK than MRSA.

"Our researchers want to know if drug-resistant bacteria are now spreading to pets, farms, livestock, plants and water, so we wanted to investigate where Klebsiella is found and monitor how it spreads to inform how best to prevent and control outbreaks
.
"

"We found it everywhere, but were surprised that the strain found in the hospital was different from the strain found in the environment, suggesting that there is little transmission between the two habitats: humans almost always catch the virus
from other people.
"

"This confirms that the best way to control these bacterial infections remains strict hospital hygiene, at least in resource-rich countries like Italy, where the chances of an outbreak caused by contact with animals or the environment are lower
than previously feared.
"

Dr Harry Thorpe, lead author of the paper and the University of Oslo in Norway, said: "We are concerned that farmers could get these bacteria from their livestock or soil, that we could get infected with contaminated salads, or that we would get sick
if we swam in an infected lake.
"

"Our study did not provide any evidence for this, however, we did find drug-resistant Klebsiella
in pets such as cats and dogs.
Veterinarians and owners should be aware of this, as these animals can pose a risk
of spreading the bacteria.
”

The consortium, called SpARK, is led by the University of Bath, but also includes researchers
from the UK (Wellcome Sanger Institute, the University of Bristol and the University of Glasgow), Norway, France, Finland and Italy.
This work, funded by the Joint Programme Initiative on Antimicrobial Resistance (JPI-AMR) and MRC, was published in Microbiology Properties
.

Professor Feil said: "This is the largest and most systematic study
conducted simultaneously in a single geographical location.

"We studied the spread of strains, however, when they exchange and acquire circular DNA fragments called plasmids, antibiotic resistance can be easily passed on to other strains
.

"Next, we want to use a technique called long-read sequencing to track the transfer
of plasmids between strains.
"