Drug Resistance in Pork: More Going On Than Appears | Wired Science | Wired.com.
The second issue to raise is that when the test results were linked back to the samples’ source, 6 of the 7 MRSA-positive RAW isolates turned out to be from the same supermarket chain, and four of them from the same store — including 4 of the 5 human-adapted ones. At that store, the meat arrived as large cuts and was broken down and packaged at the counter by store personnel, which raises the possibility of human contamination — maybe even by a single human — at point of sale. But the biggest issue, to me, is what you see in the “Resistance profile column.” Cheat sheet: O stands for oxacillin, the lab equivalent of methicillin; CL is clindamycin, E is erythromycin, and T is tetracycline. It’s the T results that I think are worth looking at. Here’s the issue. Historically, human-adapted MRSA has not been resistant to tetracycline, because tetracycline wasn’t prescribed for it; even now, tetracycline is not a first-choice drug. So, when MRSA ST398 arose in pigs in the Netherlands in 2004, and was resistant to tetracycline, that was a big red flag, because it was a change in the pattern — and because tetracycline is used in huge amounts in pigs, it was a pointer back to the involvement of farm drugs in the strain’s emergence. But in this table, there is a ton of T (tetracycline) resistance, in half of the alternative isolates and in almost all of the conventional ones, including the human types. So what that says to me is not: There’s MRSA everywhere, and therefore no point in concentrating on farm-origin drug-resistance. To me, it suggests the opposite: A marker for farm-origin drug-resistance is present in the majority of isolates found in this study, even when found on animals raised without antibiotics, and even when presumed to be coming from humans.
