https://www.vetinst.no/nyheter/antibiotikaresistente-bakterier-forste-pavisning-av-kolistinresistente-e.coli-i-importert-mat
http://www.wormsandgermsblog.com/2016/06/articles/animals/cats/new-superbug-in-dogs-and-cats-mcr-1/
A few years ago, the New Delhi metallobetalactamase-1 (NDM-1) antibiotic resistance gene attracted a lot of attention. This resistance gene can be found in (and passed between) a variety of bacteria, and bacteria possessing this gene are resistant to a wide range of drugs. A drug of last resort for those infections is colistin (a pretty toxic drug but the only option in some cases). Last November, a new resistance gene, mcr-1 was identified in E. coli from food, food animals and people. It’s now been found in numerous countries, and it’s gotten even more press over the past week since being found in the US as well. The mcr-1 gene confers resistance to colistin.
The emergence of mcr-1 is a big issue, because if you’re infected by a bacterium that is resistant to most antibiotics, and mcr-1 adds resistance to what might be the drug of last resort, that leaves you with zero treatment options. It’s been stated that mcr-1 heralds the emergence of the first truly pan-resistant bacterial infections – infections that can’t be treated with any antibiotics at all. It’s probably a fair statement.
A report in an upcoming edition of Emerging Infectious Diseases (Zhang et al 2016) describes 3 people from China infected with mcr-1 harbouring E. coli. One of the individuals worked in a pet shop, so they tested 53 dogs and cats from the store. Pretty concerningly, mcr-1 was found in 4 dogs and 2 cats. That’s bad. What makes it worse is that a few different strains of E. coli in these animals carried mcr-1, indicating they had either been infected by multiple (unidentified) sources, or mcr-1 had be passed around between bacteria in the animals’ guts. Four isolates from the dogs and the isolate from the person were the same, supporting transmission between them. Whether that means it went from dog-to-person (along with dog-to-dog) or person-to-dog can’t be discerned. It also cannot be ruled out that the animals and person were infected by some other unidentified source. Either way, this highlights the potential for interspecies transmission of mcr-1 and potentially for the spread of mcr-1 within dog and cat populations, as well as transmission of the gene between bacteria within an individual. None of those are good news, but none are really that surprising.
