Maryn McKenna

Journalist and Author

Antibiotic overuse in animals: Obama administration comes out against

By Leave a Comment

For anyone who cares about the overuse of antibiotics in food animals, and the resistant bacteria that overuse has been shown to produce, this is important news.

In testimony today, new FDA Commissioner Dr. Joshua Sharfstein announced the administration’s opposition to the use of growth promoters: sub-therapeutic doses of antibiotics used not as disease treatment, but to encourage animals to put weight on rapidly. Further, he also came out against the administration of antibiotics in food animals without the involvement of a veterinarian — a common situation out here in farm country, where veterinary antibiotics are freely available over the counter. (We discussed Scott Weese’s proposal to end that practice here.)

Both of these practices have been repeatedly linked to antibiotic resistance, and for the administration to come out against them is highly significant — not just for the struggle against resistant bacteria, but also for the movement to reduce industrial-scale agriculture, which relies on antibiotics to keep food animals healthy while they are in the close confinement of CAFOs.

Sharfstein made the announcement while giving testimony on behalf of Rep. Louise Slaughter (D-NY)’s Preservation of Antibiotics for Medical Treatment Act of 2009, which has been introduced (and opposed into nonexistence) multiple times over the past decade. (Earlier post on the legislation, including its text, here.) He said:

To avoid the unnecessary development of resistance under conditions of constant exposure (growth promotion/feed efficiency) to antibiotics, the use of antimicrobials should be limited to those situations where human and animal health are protected. Purposes other than for the advancement of animal or human health should not be considered judicious use. …
Important factors in determining whether a prevention use is appropriate include evidence of effectiveness, evidence that such a preventive use is consistent with accepted veterinary practice, evidence that the use is linked to a specific etiologic agent, evidence that the use is appropriately targeted, and evidence that no reasonable alternatives for intervention exist. FDA also believes that the use of medications for preventino and control should be under the supervision of a veterinarian. …
FDA supports the treatment of ill animals according to appropriate veterinary practice within a valid veterinary-client-patient relationship.

Also on the docket at Slaughter’s hearing:

  • Margaret Mellon, PhD, of the Union of Concerned Scientists (who specifically discussed MRSA ST398): “As long as the massive use of antibiotics continues, animals … will remain a fountain of resistant pathogens, dangerous to both animals and humans. The straightforward solution to the problem is to reduce the use of antibiotics in animal production and thereby diminish the pool of resistant organisms and traits.”
  • Robert Martin of the Pew Environment Group (Pew Charitable Trusts): “The present system of producing food animals in the United States is not sustainable and presents an unacceptable level of risk to public health, damage to the environment, as well as unnecessary harm to the animals we raise for food.”
  • And statements of support from the Chipotle restaurant chain and the Bon Appetit Management Company (which operates catering services in corporations and universities).

Of note, the Pew Commission on Human Health and Industrial Farming, which supports Slaughter’s bill, said after the hearing that Sharfstein’s proposals are only necessary but not sufficient: ““The proposed FDA position does not go far enough in this regard and would allow the continuation of conditions that necessitate the improper use of antibiotics in the first place.”

MRSA in the House of Lords — the silly, the serious

By Leave a Comment

Thanks to constant reader Pat Gardiner, we have the transcript of the UK House of Lords discussion on community MRSA, called there PVL-MRSA after the toxin. (Go to the linked page, and click down to the time-mark 3.16 pm.) It’s encouraging to see some members of a government taking MRSA seriously. The members are asking for

  • better surveillance
  • better infection control
  • consideration of MRSA as a notifiable disease
  • and promotion of both vaccine research and point-of-care diagnostics.

Hear, hear to Baroness Masham of Ilton for bringing it up.

To get to that discussion, though, you’ll have to click down through some silliness (the ghost of Monty Python is never far from the British government, is it?): a discussion at time-stamp 3.07 p.m. of whether a House of Lords restaurant can afford to serve British bacon, rather than Dutch bacon, given that British bacon is almost twice as expensive and Dutch pigs are associated with MRSA ST398:

Lord Hoyle: My Lords, I thank the noble Lord for that reply, although there is more than a whiff of hypocrisy about it. After all, I and many others on all sides of the House have argued that it should not be a matter of price. We have urged the British consumer to buy British bacon because of the higher welfare standards that are applied in this country. Will the noble Lord also take into account the presence in Dutch bacon of a deadly form of MRSA, ST398, which can cause skin infection, heart trouble and pneumonia? Is he not putting people in this country at risk, particularly as the strain has passed from animals to humans? Indeed, when Dutch farmers go into hospital, they go into isolation. Why is he putting the British consumer and those who buy bacon in this House at risk in this way?

The discussion quickly devolves into foolishness about British Tomato Week — but if you read carefully, you’ll see that behind the silliness, there are serious issues at stake: animal welfare, farming standards, truth in labeling (the Lord Bishop of Exeter advances the very newsworthy claim that pork imported from other countries is subsequently labeled “British” only because it is packaged in the UK) and movement of zoonotic pathogens across national borders thanks to globalized trade.

Sadly, the leader of the discussion — the Chairman of Committees, AKA Lord Brabazon of Tara (no, really) — appears not to have been keeping up with the news, since he notes of ST398:

As far as MRSA is concerned, I read the article in, I think, the Daily Express a couple of weeks ago. I do not think that it has been followed up by anybody else.

Apparently the Lord’s staff have not been keeping up, since MRSA in pigs in the EU has been covered by the Daily Mail, the Independent, comprehensively by the Soil Association, and by, ahem, us.

ST398 found again — in Italy

By Leave a Comment

There’s a letter in the upcoming issue of Emerging Infectious Diseases (hat tip Pat Gardiner) alerting the medical community that “pig MRSA” ST398 has been found in Italy, adding t the steadily enlarging list of countries where this strain has been identified.

(NB: Because most of these surveys are one-offs, we don’t yet know whether ST398 is truly expanding its range, or has always been there, but no one looked until now.)

Angelo Pan and colleagues of the Cremona Hospital and other institutions report that a pig-farm worker was discovered to have a severe pyomyositis (abscess buried in muscle):

The case-patient was a 58-year-old man admitted to a surgical department in Cremona, Italy, on July 30, 2007, because of a 1-week history of fever and intense pain in his right buttock. He worked on a pig farm, was obese, consumed high volumes of wine (1.5 L/day), was taking medication for hypertension, and had not had recent (Based on clinical and magnetic resonance imaging data, the diagnosis was cellulitis, pyomyositis, and pelvic multiloculated abscess of the buttock. A needle aspiration of the abscess, guided by computed tomography, was performed. Because of persistent fever (38.5°C), oral ciprofloxacin was added to the patient’s treatment regimen on day 3. Blood and abscess cultures yielded MRSA that was sensitive to glycopeptides, rifampin, linezolid, gentamicin, and mupirocin and resistant to co-trimoxazole, macrolides, clindamycin, and fluoroquinolones. After treatment was switched to vancomycin plus rifampin, the patient’s general condition improved; he was discharged from the hospital after 24 days.

An investigation was launched, and the results were intriguing:

Two fellow workers were colonized with S. aureus, 1 with methicillin-sensitive S. aureus (MSSA) and the other with MRSA. The pig farm, a farrow-to-finish production farm with 3,500 pigs, was screened for MRSA … Dust swabs were taken from 5 areas of the farm; 7 MRSA isolates were detected.
The isolate from the patient belonged to spa type t899, was ST398, carried an SCCmec type IVa cassette, and was PVL negative. The isolate from the MRSA-colonized worker was a t108 strain carrying SCCmec type V. The isolate from the MSSA-colonized worker was identified as t899. The dust swabs yielded 7 isolates: 2 belonged to t899 and carried SCCmec IVa; 5 belonged to t108 and carryied SCCmec V. The isolates obtained from the patient, farrowing area 7, and gestation area 1 were indistinguishable (i.e., same spa type, SCCmec type, and ST profile; Table), thus confirming the animal origin of transmission.

So, we have:

  • A high rate of carriage on the farm (3 of 4 workers with ST398, either MR or MS)
  • A strain-type that is both MRSA and MSSA, suggesting that in its drug-sensitive state it can acquire resistance factors rather easily
  • A PVL-negative strain that nevertheless causes invasive disease requiring more than 3 weeks hospitalization

None of these are good news.

The authors very sensibly call for more public-health attention to this strain, which — we have contended before — is long overdue:

…attention should be given to the emergence of MRSA strains among animals, and continuous surveillance in humans should monitor the extent of disease from MRSA ST398, especially in areas of intensive animal farming. Collaboration between infectious disease specialists, microbiologists, and epidemiologists, on both the human and the veterinary sides, should be strengthened and readied for appropriate action whenever complex, zoonotic, public health issues occur.

The cite is: Pan A, Battisti A, Zoncada A, Bernieri F, Boldini M, Franco A, et al. Community-acquired methicillin-resistant Staphylococcus aureus ST398 infection, Italy [letter]. Emerg Infect Dis [serial on the Internet]. 2009 May. DOI: 10.3201/eid1505.081417

Does ethanol production produce resistant bacteria too?

By Leave a Comment

One of the challenges of disappearing down the rabbit hole of a gnarly chapter — gee, it’s dark down here — is that I get behind on my RSS feeds, and suddenly every entry in my Google Reader is at 1000+ and it’s all just too daunting.

So, trying to catch up a bit, I found two related, interesting and troubling stories from the Associated Press (4 April) and the online magazine Grist (7 April — yes, I said I was behind…).

Synopsis/synthesis: Corn-based ethanol, former darling of the energy and large-scale agriculture industries, suddenly doesn’t look like such a good idea – and not just because the market for it is crashing. Turns out that ethanol is made by adding yeast and sugar to corn mash; the yeast convert the carbohydrates to the alcohol that is the basis of the fuel. (Yes, just like making beer.) However, the mash is particularly attractive to Lactobacillus and other bacteria that produce lactic acid as a waste product rather than alcohol, and a tank full of lactic acid doesn’t make very good fuel. So, to keep the bacteria under control, ethanol producers add antibiotics. Specifically, penicillin and erythromycin — you’ll recognize those — and tylosin and virginiamycin, two macrolides, related to erythromycin, that are approved in the US for veterinary use.

Now, the problem with this practice, as you might predict, is that if the mash is not appropriately dosed, the presence of antibiotics within it can prompt some of the bacteria to develop resistance. (Here’s an article from the trade magazine Ethanol Producer discussing just that possibility.)

And the further complication of this is that the leftover mash, now called “distillers’ grains,” is sold as animal feed. Ask yourself: Where in animal production are animals most likely to eat grains? Answer: At finishing, in feedlots. In other words, fermented grains that may contain antibiotic residue, and may contain resistant bacteria, are being sold as feed to animals that are already being raised in conditions that have been shown to foster the development of resistant bacteria through subtherapeutic and prophylactic antibiotic use. In fact, some research has drawn an explicit link: Kansas State University scientists have found higher levels of E. coli O157 in the guts of cattle that were fed distillers’ grains.

All of this was new to me, but there’s an additional facet to the story that the AP and Grist pieces don’t highlight, and that just makes my head hurt: the use of virginiamycin. For those new to the story, virginiamycin is an allowed, widely used veterinary antibiotic in the US. However, it is not used in the European Union: It was banned there in 1998 because the EU’s ag authorities believed that it promoted resistance to the drug Synercid (quinupristin+dalfopristin), which is a drug of last resort against vancomycin-resistant bacteria such as VRE. (Here’s a Lancet paper that talks about that resistance mechanism.) Synercid was approved by the FDA in 1999 — two years after Synercid resistance had already been found in the US. (For a long but cogent explanation of the complex story of virginiamycin, see the book The Killers Within.)

So, just to recap: We have an industry whose long-term earnings are shaky, whose economic survival is partially secured by the sale of its waste product, and which via that waste product is putting antibiotic residues and antibiotic-resistant bacteria into the environment, and is conveying them into food animals, and is making particular use of an antibiotic that other countries have banned because they believe that, via its use in animals, it exerts an adverse impact on human health.

Something to remember the next time ethanol subsidies come up.

More MRSA in pigs, in Portugal

By Leave a Comment

A brand-new report, in a letter to the International Journal of Antimicrobial Agents, indicates that ST398 “pig MRSA” has been found in Portugal for the first time.

Constanca Pomba and colleagues from the Technical University of Lisbon swabbed and cultured the noses of pigs and veterinarians on two pig farms in different regions of Portugal, and also checked the air at both farms.

What they found:

  • On Farm A: All pigs and the veterinarian positive for ST398, the pig-origin strain that has been found so far in Iowa, Ontario, the Netherlands, France, Denmark, Germany and Austria and has, depending on the country, caused human disease and/been found on retail meat. The veterinarian was transiently colonized, which is to say that he was not carrying the bug long-term.
  • On Farm B: All pigs — but neither of two veterinarians — positive for a different MRSA strain, CC (or ST) 30. This is very interesting, because CC30 is usually a drug-sensitive strain (MSSA, methicillin-sensitive S. aureus), and has been found in pigs primarily in Denmark and France. In Portugal, it is a human MSSA hospital-infection strain.

Strains from both farms were resistant to tetracycline; this is turning out to be a great marker for these strains having emerged due to antibiotic pressure in animals, because tetracycline is very commonly used in pigs. but not much used for MRSA in humans. The strains have the genes tetK and tetM, so they are resistant not just to tetracycline itself, but to the whole class of tetracyclines including doxycycline and minocycline. The Farm B strains also carried the gene ermC, which encodes resistance to erythromycin.

So what does this tell us?

  • First, that (once again), every time people look for ST398, they find it; it is now a very widely distributed colonizing bug in pigs, and is repeatedly spreading to humans. What we don’t know, because all these studies are so new, is whether ST398 is actively expanding its range, or has been present in all these countries for a while. We have been anticipating its presence or spread (take your pick at this point) through the European Union because of open cross-border movement of food animals, meat, and agriculture and health care workers.
  • And second, it should tell us that it is really past time to start looking for this more systematically. Every finding of ST398 that we have (long archive of posts here) is due to an academic research team who decided to look for the bug. None of the findings, to date, have come from any national surveillance system. (NB: Except for the first human colonizations in the Netherlands, which were found as a result of the national “search and destroy” rules in hospitals.)

Of note, the European Union is running a study now that is supposed to report ST398 prevalence at any moment (as they have been saying since 2007). It is not expected to be comprehensive, since it was piggy-backed onto another study, but it is something. The US government has not been so enterprising.

The cite is: Pomba, C. et al. First description of meticillin-resistant Staphylococcus aureus (MRSA) CC30 and CC398 from swine in Portugal. Intl J Antimicrob Agents (2009), doi: 10.1016/j.ijantimicag.2009.02.019

Appearing today on The Ethicurean

By Leave a Comment

Constant readers, I want to let you know that the terrific food policy blog The Ethicurean (motto: “Chew the right thing“) very kindly had me over to do a Q&A on MRSA in meat. Please take a look and let them have some clicks: They are smart people thoughtfully elucidating a difficult subject, and worth following.

(And I would say that even if they hadn’t called me the “Superbug supersource,” honest.)