NDM-1 in Salmonella...ugh!
NDM-1 (New Delhi metalloproteinase 1) is a little bacterial gene that's attracted a lot of attention (and controversy, due to its name). NDM-1 can be picked up by certain types of bacteria, making them resistant to a whole lot of antibiotics. Some bacteria that carry NDM-1 are resistant to virtually every available antibiotic, which raises the spectre of the "untreatable infection."
Since it's discovery, NDM-1 has been found in multiple countries, often in people that were in India as tourists (or "medical tourists" who traveled to India for medical procedures they couldn't have done in their own countries), and in a few different types of bacteria. Recently, NDM-1 was found in an American upon his return from India, this time in Salmonella (Savard et al. 2011, Antimicrobial Agents and Chemotherapy).
The 61-year-old man was hospitalized in India in late December 2010 following a severe bleed in his brain. He was transferred back to the US on January 25, 2011. Upon arrival, he developed a fever and a multidrug-resistant bacterium, Klebsiella pneumoniae, was isolated from his breathing tube. This was concerning by itself, but later, Salmonella Senftenberg was isolated from the man's rectum. The strain was highly atimicrobial-resistant and was determined to carry the NDM-1 gene.
There have been complaints from people in India about the stigma associated with the "New Delhi" component of the name. In hindsight, many people wish it had been named differently because of this, but at least at the moment, it's undeniable that India is a (or the) hotbed of NDM-1. It's been found in various bacteria from water and seepage samples in New Delhi, but this is the first report in Salmonella. It's concerning because of the difficulty that would be encountered treating highly resistant Salmonella in infected people. Usually, antibiotics aren't needed when someone has salmonellosis, but when they are needed, it's important that they work. Highly drug resistant strains increase the chance of a bad outcome if ineffective antibiotics are used initially (before it's determined that the strain is resistant).
NDM-1 has not been reported in animals... yet. I assume it's inevitable that it will occur, since this gene appears quite able to move between bacterial species. If it increases in humans and in human-feces-contaminated sources like water, exposure of animals will certainly occur. If NDM-1 containing bacteria establish themselves in the intestinal tracts of healthy animals, it's going to be much harder to control.
NDM-1, a new threat?
"NDM-1 superbugs" have received a lot of press the last day or two. That's lead to questions about whether there may be any risks for pets.
It's good to see that people are thinking about how this might affect other animal species. That's a thought process that would have been rare a few years ago, and which was probably fostered by the emergence of MRSA in animals.
What it NDM-1?
- NDM-1 stands for New Delhi metallo-beta-lactamase 1. It is a type of beta-lactamase, an enzyme that inactivates certain antibiotics (those of the beta-lactam class). The concern with NDM-1 is that it inactivates carbapenem antibiotics, an important class of drugs that is often used to treat serious and life-threatening infections.
Where is it a problem?
- It's currently mainly a problem in India and Pakistan.
Will is spread to other regions?
- Probably. It's easy for people to travel around the world quickly, and it's easy for new microorganisms to travel with them. A bug that originates in one region can very easily spread across the planet. NDM-1 has been found in a few other countries, including Australia, parts of Europe and Canada. There is concern that the increase in health tourism (traveling to countries like India for cheap and quick procedures like elective surgeries) will result in spread of NDM-1, since people could pick up the bug in hospitals and bring them home. Transmission of NDM-1 in hospitals from patients that had healthcare procedures abroad has been documented in the UK. People traveling to regions where the organism is present for other reasons are also possible sources.
Can it affect pets?
- Probably. Two important types of bacteria, E. coli and Klebsiella spp, can carry NDM-1 (and probably other related bacteria can as well). These can cause infections in many different species. As more people carry bacteria with NDM-1, there's a greater chance that pets will be exposed, as we've clearly seen with MRSA. Dogs that visit human hospitals and pets owned by people who visit India for healthcare are probably at greatest risk, with pets of people who have been hospitalized and pets of healthcare workers likely also at increased risk.
What can we do to reduce the risks?
- Nothing specific. The most important factor here is control of NDM-1 in human hospitals. At the animal level, there's nothing in particular we can do about NDM-1 at the moment. The keys are prudent use of antibiotics (to reduce the likelihood that resistant strains will get established in pets), good general infection control in households and veterinary hospitals (to reduce opportunistic infections by bacteria that can carry NDM-1), and making sure that cultures are taken when infections are present (to find out if/when this becomes a problem).
