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Published Date: 2012-09-16 14:03:23
Subject: PRO/AH/EDR> NDM-1 carrying Enterobacteriaceae - USA (02): feline
Archive Number: 20120916.1294263

NDM-1 CARRYING ENTEROBACTERIACEAE - USA (02): FELINE
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Date: Wed 12 Sep 2012
Source: Wired.com [edited]
http://www.wired.com/wiredscience/2012/09/ndm-icaac-3

News from the ICAAC (Interscience Conference on Antimicrobial Therapy and Chemotherapy) meeting: The "Indian superbug" NDM-1, actually a gene which encodes an enzyme which confers resistance to almost all known antibiotics, has been found for the first time in a pet, somewhere in the USA.

When you consider the close contact we have with our pets - letting them lick us, smooching them on the head, allowing them to sleep on the bed - you'll understand why this could be such bad news.

The finding was announced by Dr. Rajesh Nayak, a research scientist with the FDA's National Center for Toxicological Research in Jefferson, Ark. (The research was carried out by Dr. Bashar Shaheen, a post-doc in Dr. Nayak's lab.) The gene (technically blaNDM) was found in isolates of _E. coli_ that they received from Dr. Dawn Boothe of Auburn University -- part of a project, Nayak said, in which Boothe receives bacterial samples from veterinary laboratories all over the USA. Of the 100 isolates they received from Boothe, 6, all from a single animal, contained NDM-1.

The gene and the enzyme it encodes were first identified in 2008 in Sweden, in a man of Indian origin who had gone home to India, was hospitalized, recovered, and then was hospitalized again in Sweden. The _Klebsiella_ found in the man's urine was resistant to a huge array of drugs, including a last-resort category reserved for very serious infections that are known as carbapenems. In 2009, bacteria containing the NDM-1 gene, which travels on several plasmids, pieces of DNA that can move easily between organisms, were found in the UK, and its Health Protection Agency put out a national alert. In 2010, bacteria containing NDM-1 were found in the USA for the 1st time, in 3 residents living in different states.

What the original patient, the US patients and most of the UK cases all had in common was ties to India and Pakistan: medical treatment (either emergencies or elective surgery), family ties, or travel back and forth. The gene's ... acronym stands for "New Delhi metallo-beta-lactamase". Additionally, the original researchers published studies of patients in South Asia, demonstrating that organisms containing the gene were not confined to hospitals but circulating widely in everyday life, and also analyses of water from New Delhi that showed the bug was moving through the water supply. Meanwhile, NDM-1 continued to spread, to more than a dozen countries so far.

And now, according to Shaheen and Nayak's finding, possibly entering households and families in the same covert manner. I spoke to Nayak after his ICAAC presentation Tuesday, 12 Sep 2012. He said that very little is known about the source of the bacterial samples, including the identity of the family and the cat. "The reason why we don't know is these were not collected by us, and they were not collected by Dr. Boothe; they were collected by veterinarians," he said. "So a family comes in, says 'My cat is not feeling well,' and the veterinarian collects blood, urine, whatever, and sends them in. There is no history associated with them."

The timing of the sample is perplexing, he agreed. The isolates were received between 2008 and 2009 from the labs where vets sent them, meaning that the NDM-1 in the unknown cat was collected at the same time as the earliest recognition of the resistance factor in Europe, and at least a year before NDM-1 was perceived in the USA.

He emphasized that it isn't known whether the cat passed NDM-1 on to its family (or, conversely, whether the family were responsible for giving the bug to their pet). If that happened, it would not be the first time that bacterial traffic between pets and their humans has made one or the other sick. There is a long literature of MRSA passing back and forth between people and their cats and dogs, in some cases making the humans sick and in some cases making the animals very ill. (Coincidentally, this also was discussed at ICAAC by Dr. Tara Smith of University of Iowa, at almost the same time that Nayak was presenting his work.) And Nayak's group actually made the NDM-1 finding while following up two pieces of research they published last year about organisms in pets which had the resistance pattern ESBL -- troubling, but still susceptible to carbapenems, and thus one step away from NDM-1.

"Carbapenem resistance is such an important issue," Nayak told me. "Carbapenems are the last line of defense. And companion animals are so close to humans; what if there is a transfer from one to another? It is possible, that is all I can say; it is a distinct possibility."

[Byline Maryn McKenna]

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Contributed by:
Merritt Clifton
Editor, Animal People
Clinton, WA
<anmlpepl@whidbey.com>

[ProMED thanks Merritt Clifton for the contribution. He also offered the following commentary:

Given the origin of the "superbug" enzyme in India and Pakistan, and that it turned up in the USA in a cat, I'd bet that it is of rodent origin, and that the host species are mice or rats.

In India and Pakistan the rodent populations are controlled largely by street dogs, who like other scavenger species are strongly resistant to most opportunistic infections that can be contracted from prey and carrion. Street dogs probably don't show much sign of contracting this "superbug" that people would recognize, not least because the illnesses and deaths of street dogs are seldom noticed unless they involve rabies or occur in large numbers. Additionally, because people in India and Pakistan usually do not allow dogs to come inside their homes, even if they are not actually dog-aversive, street dogs are relatively unlikely to spread diseases that require close contact to people in that part of the world, other than diseases like rabies that are inflicted by biting.

In the USA, though, cats are the front line household rodent predator, and cats don't really do much scavenging, so cats are notoriously more susceptible to infections and to transmitting infections than dogs. Also, the USA has only about 4 million dogs per year who are found roaming at large, compared with a feral cat population of from 6 million in the dead of winter to 12-13 million in midsummer "kitten season," plus about 30 million pet cats who spend time outside -- and even fully indoor cats may have some opportunities to hunt rodents.

I'm going way out on a limb here, but I suspect what happened is that mice or rats stowed away in a cargo of some sort that was flown to the USA from India or Pakistan, and then began spreading the enzyme in question among acquaintances and kin near where they landed. Eventually a cat bagged one of the infected rodents.

Humans may be infected meanwhile by droppings or urine, as with most other diseases transmitted by rodents. This is almost certainly going on in India and Pakistan too, and has almost certainly been going on for some time, but unrecognized because there are so many other poorly controlled and documented infectious diseases among the people most at risk." - Mod.LL

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