NDM-1 in a cat

When bacteria containing NDM-1 (New Delhi metallobetalactamase 1) were first identified a few years ago, I talked about it during presentations as something bad that's coming our way. NDM-1 is an enzyme that gives the bacteria that possesses it resistance to a huge range of antibiotics, to the point that few or no viable treatment options are available. Given the close relationship between animals and humans, I figured it was only a matter of time before cases were identified in animals, especially household pets. A presentation by an FDA researcher at the 2012 Interscience Conference on Antimicrobial Agents and Chemotherapy (ICAAC) has confirmed the finding of NDM-1 in E coli from a pet cat in the US. I can't take much credit for foresight because it was pretty predictable, but it re-affirms concerns about emerging diseases and how infectious pathogens can move between people and animals.

Not much is known about this current case, since the E coli isolate was submitted for testing as part of a large ongoing surveillance study by Dr. Dawn Boothe of Auburn University. At this point, it's unclear whether the cat had been on antibiotics earlier, whether the owner had been diagnosed with the infection, whether the owner had traveled to areas where this bug was first found (e.g. India), and other relevant pieces of information remain unknown (or at least unreported).

The cat was positive for the NMD-1 E.coli on multiple samples.  The most intriguing aspect of this case is the fact that the culture samples from the cat were collected in 2008 and 2009 - at least a year before NDM-1 was first identified in the US. That's strange and concerning, and raises lots of questions about where this super-E.coli originated.

Some possible origins of the NMD-1 E.coli in this cat include:

  • The owner may have traveled to an area where the bug was present, became a carrier and spread it to his/her cat upon returning home.
  • The owner could have been infected when traveling, but it the infection may have been minor such that it didn't require medical care or a culture wasn't taken (so no one knew it was being caused by a super-bug), and subsequently the owner passed it on to the cat. (Remember that NDM-1 is a major concern because very few antibiotics are effective against it. However, the enzyme doesn't make the bacterium that carries it inherently more able to cause disease, so minor infections are possible.)
  • On ProMed, the moderator stated that he believes stowaway rodents from India or Pakistan likely carried the bug to the US and spread it amongst other rodents, with eventual exposure of the cat through catching an infected rodent. It's possible but it's a major stretch, in my opinion.
  • Perhaps the cat came from one of those endemic regions. That's pretty unlikely but there's a lot of animal movement around the world, with very little regulation, so it is possible.

We may never know how this cat got infected, but this case should be a reminder that we need to pay attention to animal populations in parallel with the human population. I keep saying it, but getting action has been difficult. People like to talk about "One Medicine," but actually getting people to practice "One Medicine" has been easier said than done.

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