Superbug from human eye drops outbreak spread to dogs

Two dogs treated at a veterinary hospital in New Jersey last year have tested positive for a rare, drug-resistant strain of bacteria linked to a fatal outbreak blamed on now-recalled eye drops that had been used in humans, a CDC investigator said Friday.

The animals were infected by a bacteria known as carbapenemase-producing carbapenem-resistant Pseudomonas aeruginosa, found in swabs of the lung and ear of two dogs from different owners at the hospital. 

Testing of the bacteria from the dogs found it to be "highly genetically related" to the germs behind an outbreak last year that ultimately sickened 81 human patients across 18 states. By the end of that outbreak, 14 patients lost their vision and four died.

Germs that produce carbapenemase are especially worrying to health officials in part because they can break down carbapenem antibiotics, a class of drugs typically reserved for infections resistant to other treatments, and can easily spread their resistance genes to other pathogens.

"So now that this bacteria has been introduced into the U.S. from the artificial tears, this resistance could spread," the CDC's Emma Price said Friday, presenting her team's findings at a conference of the agency's Epidemic Intelligence Service. 

The CDC bills its annual conference as a meeting of the agency's up-and-coming "disease detectives," presenting updates on their work across a swath of investigations and studies.

Price said one of the dogs had been swabbed while being seen at the hospital to try to diagnose a chronic cough. From the other dog, veterinarians had been trying to figure out the culprit of a stubborn ear infection.

Swabs were sent to an academic veterinary laboratory in Pennsylvania, which spotted uncommon signs of resistance in the germs and uploaded the genetic sequence of the strain to a national database — prompting the CDC and state health authorities to launch a probe.

"Because they had a grant and a veterinary microbiologist works there, he did his great due diligence and uploaded the results. That's how we got the notification, because the strain matched the outbreak strain," said Price.

Meanwhile, the eye drops outbreak in humans also prompted a crackdown by the Food and Drug Administration across the industry, leading to millions more bottles of over-the-counter brands yanked from shelves and banned from import. 

The initial outbreak was blamed on contaminated eye drops produced at a factory in India where Food and Drug Administration inspectors ultimately found dirty equipment and a long list of shortcuts in hygiene procedures. Other factories have also turned up worrying issues, ranging from barefoot workers to falsified records.

The FDA this year issued a warning for veterinary hospitals and pet owners urging them to check their supplies for recalled eye drops, after a report of an infection.

"The adverse event was in a cat that developed an eye infection after being treated with the drops. However, testing was not able to conclusively prove that the eye drops caused the infection," an FDA spokesperson told CBS News in March, after the warning.

Price said interviews with the two pet owners turned up no obvious explanations for how the drug-resistant germs got into their dogs. Neither had traveled internationally or visited human hospitals.

"Neither dog owner recalled using the tears [eye drops], although we do acknowledge the difficulty of recalling over the past year," said Price.

Both pets ultimately recovered and are now doing well, Price said. But their findings worried investigators, who found gaps in the animal hospital's infection prevention routines. Those could have offered a path for the germs to have spread from staff or other pets. 

Staff at the hospital had "limited" options to clean their hands, falling short of recommendations to offer hand sanitizer in every treatment area.

"There was also limited availability and just general lack of use of personal protective equipment, especially gloves," said Price.

Other potential brewing grounds for bacteria included equipment that was shared between staff also had "visible soiling and dust accumulation," and supposedly clean supplies which were stored within the splash zone of sinks. 

"These findings aren't specific to this hospital. This is part of a wider lack of emphasis of infection prevention and control in the veterinary setting," Price said.

One of the dogs also lives at home with three other pets, she said, prompting concern that the drug-resistant bacteria may have "colonized" the dog long-term and could eventually spread to others. 

Human patients are sometimes colonized for months to years by infections of Pseudomonas aeruginosa, according to the CDC.

"Fortunately the owners were not immune compromised, but we did alert them to the fact that there could be potential transmission to them and to alert their physicians as well for future healthcare visits," Price said, "and ideally keep the dogs away from other dogs in the future, which we understand is a difficult thing to do."

Alexander Tin

Alexander Tin is a digital reporter for CBS News based in the Washington, D.C. bureau. He covers the Biden administration's public health agencies, including the federal response to infectious disease outbreaks like COVID-19.

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