More MRSA Found In U.S. Retail Meat (Turkey, Too) - Tetracycline-resistant

[Gert van der Hoek]

Some snips from Maryn McKenna's blog:

More MRSA Found In U.S. Retail Meat (Turkey, Too)

There are two new studies out that confirm, once again, that drug-resistant staph or MRSA — normally thought of as a problem in hospitals and out in everyday life, in schoolkids, sports teams, jails and gyms — is showing up in animals and in the meat those animals become.

The strain of staph that shows up in farm animals, known as “livestock-associated” MRSA or MRSA ST398, first emerged in pigs in the Netherlands, and has been widely identified in retail meat in Europe. (You can find a long archive of posts on ST398 here, and more here.) But that same strain has been difficult to identify in the United States. That may be due in part to the US having a uniquely massive epidemic of community-associated MRSA, far larger than in any other country, which likely both obscures any animal epidemic from detection, and possibly also fills the ecological niche that livestock-associated staph might otherwise occupy. But, it must be said, there’s also remarkably little political will to look for livestock-associated MRSA (though the US Department of Agriculture has now funded a study).

They found something else interesting in this research. One of the hallmarks of ST398 has been that — unlike human-associated MRSA strains — it is resistant to tetracycline. That’s an important signal. While human MRSA is multi-drug resistant, it is usually still susceptible to tetracycline, because tetracycline is not used in human MRSA infections and thus the bug has no exposure that encourages it to evolve resistance. However, tetracycline is very commonly given to animals raised for meat in confined conditions, which is presumably where ST398 worked up or picked up its tetracycline-resistance gene.

In this paper, all of the staph found in pork and turkey was tetracycline-resistant even when it was not MRSA (which, definitionally, is resistant to methicillin or its close analog oxacillin). Six of the seven staph-containing turkey samples were t034, and one was t337, which is associated with another MRSA strain that has emerged in pigs in China. “This suggests that turkeys, in addition to pigs, are a possible reservoir for both the ST398 and ST9 strains in the United States,” the authors say.

More

 

[Gert van der Hoek]

Re: More MRSA Found In U.S. Retail Meat (Turkey, Too) - Tetracycline-resistant

Tetracycline resistance could be a good marker for MRSA CC398, a.k.a. pig MRSA

High prevalence of spa types associated with the clonal lineage CC398 among tetracycline-resistant methicillin-resistant Staphylococcus aureus strains in a Spanish hospital.

J Antimicrob Chemother. 2011 Nov 28;

Authors: Lozano C, Rezusta A, G?mez P, G?mez-Sanz E, B?ez N, Martin-Saco G, Zarazaga M, Torres C

Abstract

OBJECTIVES: CC398 (67.3%), CC1 (11.5%), CC5 (11.5%) and CC8 (9.6%). A novel sequence type (ST), ST2077, belonging to CC398 was identified. Most MRSA CC398 strains were typed as SCCmecV-agrI. In addition to β-lactam resistance, isolates showed resistance to (gene/number of strains): tetracycline [tet(K)/36, tet(L)/8 and tet(M)/48], macrolides and lincosamides [erm(B)/6, erm(C)/25, erm(T)/2, msr(A)/msr(B)/4 and mph(C)/4], aminoglycosides [aac(6')-Ie-aph(2')-Ia/8, ant(4')-Ia/13 and aph(3')-IIIa/15], trimethoprim [dfrS1/2 and dfrK/3] and mupirocin (mupA/3). Strains investigated for mutations mediating quinolone resistance revealed an S80F exchange in GrlA and different changes in GyrA. Three strains were Panton-Valentine leucocidin-positive (ST8 and ST94) and 41 strains were cna-positive. All MRSA isolates were negative for the genes tst, eta, etb and etd.

Conclusions: Tetracycline resistance could be a good marker for MRSA CC398, although this resistance can also be found in other lineages.

MedicineJournalFeeds