Pets found to be carrying bugs resistant to humans-only antibiotic

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Pet cats have been found to be harbouring bacteria resistant to a ‘last resort’ human antibiotic (Nick Ansell/PA)

Pets brought to a small animal hospital in the UK have been found to be harbouring bugs resistant to a “last resort” antibiotic not licensed for veterinary use.

Linezolid is an advanced antibiotic that was approved in the UK in 2001. It is used to treat intractable human infections including those caused by the “superbug” MRSA (methicillin-resistant Staphylococcus aureus) but not given to animals.

Yet three cats and a dog have been found to be carrying bacteria “armed” with a gene that confers high levels of resistance to linezolid.

The animals had all been taken to the same small animal hospital from different households.

Linezolid-resistant Enterococcus faecalis bugs were isolated from three wound swabs from two cats and the dog, as well as a rectal swab from a third cat.

The discovery implies that resistance to one of a vanishingly small number of last resort antibiotics can spread between different bacterial populations in animals and humans.

Dr Katie Hopkins, from Public Health England, who led the research, said: “This is concerning as transmission of this organism to owners carries the potential for spread to other bacteria, including Staphylococcus aureus.

“This may lead to difficult-to-treat infections. In order to minimise transmission of resistant bacteria between companion animals and people, veterinary surgeries need to ensure adequate cleaning takes place and pet owners should wash their hands after handling pets.”

The gene that enables bacterial resistance to linezolid is known as optrA.

Dr Hopkins said it was thought to be the first time optrA-positive enterococci had been identified in pets in the UK.

As part of routine testing for antibiotic resistance, the swab samples had been referred to a specialist Public Health England laboratory.

Besides all four isolates testing positive for optrA, there were indications of animal-to-animal transmission.

However, thanks to prompt cleaning and decontamination, there was no evidence of any human picking up an infection from the pets, said Dr Hopkins.

She added: “Our findings further the ‘One-Health’ view that antibiotic-resistant bacteria can be shared by animals and humans, although the direction of transfer is often difficult to prove.

“We currently do not know the prevalence of linezolid-resistant enterococci in companion animals and therefore a joint approach to monitoring emergence and dissemination of resistance mechanisms of public health importance is needed.”

The research is being presented at the European Congress of Clinical Microbiology and Infectious Diseases (ECCMID) meeting in Amsterdam.

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