Food and Health Rethought

More on how conventionally produced beef and chicken are breeding grounds for bactera

A piece of research (PDF) [was] released Friday morning in the journal Clinical Infectious Diseases 

A team of researchers from Arizona bought meat and poultry in five cities across the United States, tested them for bacteria, and found this: 47 percent of the samples contained the very common pathogen Staphylococcus aureus, and 96 percent of those isolates were resistant to at least one antibiotic. Of more concern: 52 percent of those staph isolates were resistant to at least three antibiotics that are commonly used in both veterinary and human medicine.

That is, roughly one in four packages of meat and poultry from across the United States contained multidrug resistant staph.

Among the types of meat tested, turkey carried the most resistance, with 77 percent of the meat samples showing at least some; that was followed by pork (42 percent), chicken (41 percent) and beef (37 percent). Interestingly, it wasn’t all the same staph. Though there was a great diversity of staph types, each animal species seemed to carry mostly one sequence type or strain of staph: ST1 in pigs, ST5 in chickens and ST398 in turkey. (More on that below.)

We found that each of the meat and poultry types had their own distinctive staph on them. That provides strong evidence that food animals were the primary source of the resistant staph. The source wasn’t human contamination of the meat at slaughter, or when it was packaged for retail sale.”

hat surveillance system doesn’t look for MRSA, and in the past few years, because of those pig findings, there has been a lot of pressure to add MRSA to the list.

But even if we did perform nationwide testing for MRSA in meat, that would not have found the multi-drug resistant strains revealed in Price’s work today — because most of them were not MRSA.

More from the original study:

A new multidrug-resistant S. aureus strain, ST398,has emerged that predominantly colonizes people working in food animal production. First discovered in 2003, ST398 now makes up a substantial proportion of the community-acquired methicillin-resistant S. aureus (MRSA) cases in the Netherlands. Multiple studies have demonstrated the high prevalence of multidrug-resistant S. aureus, including ST398, among intensively raised swine in the European Union, Canada, and the United States, but few studies have been conducted to measure its prevalence in US food products. 

 All isolates were screened against antibiotics that are commonly used to treat severe MRSA infections. We identified 1 vancomycin-intermediate-resistant isolate and 1 daptomycinresistant isolate. Vancomycin, daptomycin, and their analogs were never approved for US food animal production; therefore, these findings were unexpected and may suggest origins other than US food animals.

European and North American studies indicate that ST398 can successfully colonize and infect humans.

Conventional concentrated animal feeding operations (CAFOs) provide all the necessary components for the emergence and proliferation of multidrug-resistant zoonotic pathogens. In the United States, billions of food animals are raised in densely stocked CAFOs, where antibiotics are routinely administered in feed and water for extended periods to healthy animals.

I like how the study concludes that current conditions for raising animals are really ideal for producing drug resistant strains of bacteria. This is ridiculously scary. On the one hand, it’s a reason to eat more grass fed meat and pastured poultry. On the other hand, it’s arguable that more regular is needed for conventional farming methods.