Maryn McKenna

Journalist and Author

Bill in Congress: “Preservation of Antibiotics for Medical Treatment” Act

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Important news for anyone concerned about the spread of “pig MRSA” ST398: Rep. Louise Slaughter (D-NY) and Sen. Edward Kennedy (D-MA) have introduced a bill that would restrict important classes of antibiotics for use against disease only, taking them out of the realm of subtherapeutic use or growth promotion in agriculture. The bill would allow the use of the antibiotic classes for disease in animals as well as in humans; the intent is to preserve the drugs’ effectiveness for as long as possible.

The text of the bill, the Preservation of Antibiotics for Medical Treatment Act of 2009, is here.

A Reuters story in which Slaughter predicts the bill will have a difficult time is here; she has introduced it several times in the past decade, but it has never made it through.

Support from the Pew Commission on Industrial Farm Animal Production is here. An earlier version was supported by the American Academy of Family Physicians here.

The National Pork Producers’ Council’s response is here.

(Hat tip to Barry Estabrook at Politics of the Plate and to Melinda Hemmelgarn, the FoodSleuth.)

Industrial farming, bacterial spread 2 – or: Flies. Ick.

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There’s a brand-new paper in the journal Science of the Total Environment that has some unnerving things to say about the link between very large scale farming, use of antibiotics in food animals, development of resistant organisms, and transmittal out into the larger environment.

Via flies.

Not to be unscientific, but: Ick.

A team from the Bloomberg School of Public Health at Johns Hopkins (who have done a number of studies on the spread of antibiotic-resistant organisms from farms to the outside world) decided to test the links in a chain of hypothesis that goes like this:

  • Antibiotics are used in large amounts in poultry production.
  • Antibiotic-resistant organisms are produced within the birds.
  • Antibiotic-resistant organisms leave the batteries via poultry litter (“excreta, feathers, spilled feed, bedding material, soil and dead birds“).
  • Poultry litter is stored in open sheds until it can be used as a soil amendment.
  • Flies have unrestricted access to poultry litter.

The tests were: sampling poultry litter from three farms in the Delmarva Peninsula (for non-US readers, that’s a portmanteau word for contiguous areas of the states Delaware, Maryland and Virginia, home to about 600 million chickens each year); trapping flies at 8 locations within 100 meters of farm boundaries; and assaying both litter and flies for the presence of resistant organisms and resistance genes.

And the findings were: Oh, lots and lots. Litter piles at all three farms contained resistant organisms — E. faecium, E. faecalis and our particular interest, Staphylococcus (multiple species, including three strains of S. aureus) — throughout the 120-day study period. All 8 fly traps did as well. All of the litter contained enterococci and staph strains that were resistant to 3 or more antibiotic classes. Seven of the 8 fly traps yielded multi-drug resistant enterococci, and 3 yielded multi-drug resistant staph. The resistance factors identified were for drugs that the FDA classifies as “critically or highly important” to human medicine: “penicillin, tetracyclines, macrolides, lincosamides, aminoglycosides and streptogramins.” Oh, and the fly species captured in the traps had an average range of 2 miles.

Of note, among the isolates discovered was one staphylococcus with high-level resistance to vancomycin.

The authors say:

This study strongly suggests that flies in intensive poultry production areas, such as the Delmarva Peninsula, can disperse antibiotic resistant bacteria in their digestive tracts and on their exterior surfaces. Dispersion of resistant bacteria from poultry farms by flies could contribute to human exposures, although at present it is difficult to quantify the contribution of flies. Flies may also transfer bacteria from fields amended with poultry waste.

The cite is: Graham JP et al., Antibiotic resistant enterococci and staphylococci isolated from flies collected near confined poultry feeding operations, Sci Total Environ (2009), doi:10.1016/j.scitotenv.2008.11.056. The ahead-of-print abstract is here.

More MRSA, more meat – poultry, this time

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Constant readers: Fresh from the journal Emerging Infectious Diseases — posted AOP (electronic publication/ahead of print) this afternoon — comes more news of MRSA ST 398, the “pig strain,” in food animals. This time, it’s chickens, in Belgium.

The authors (from Ghent University and the Veterinary and Agrochemical Research Center in Brussels) took swabs from living chickens — laying hens and broilers — from 24 farms, 50 layers and 75 broilers total; one broiler-raising farm was sampled twice. They found no MRSA in the layers, which is important for reasons I’ll get to in a moment, and ST 398 in 8 broilers. From each chicken, they took two samples, nasal and cloacal, and in the 8 positive chickens, they got 15 MRSA isolations; one cloacal swab was negative. Of the positive chickens, several (I deduce three, but the math is a bit cloudy) were spread across the two visits to the farm that was sampled twice. Since chicken farms are depopulated between batches — yes, just what it sounds like, farms sell/kill all the birds and clean the place — that finding suggests that MRSA is persisting in the environment on that farm.

Important point: This strain was ST 398, which we here have been calling the pig strain from many previous findings, most of them in pigs. However, ST 398 is an identification using a particular technique called MLST (multi-locus sequence typing), which is used for this strain because the standard typing method, PFGE (pulsed-field gel electrophoresis), did not return a readable result when the strain was first identfied back in 2004. (Trivia: That’s why the initial reports of this strain called it NT, for “nontypeable.”) It’s becoming increasingly clear, though, that ST 398 is actually a category, not a single strain. And within that category, today’s research is a new find: a strain with the unusual spa type t1456, which has only been found 10 times in the past three years, in Germany and the Netherlands, not in Belgium. The author suggest that this particular strain may be adapting to poultry in the same manner that the ST 398 we have been talking about (different spa type — sorry, I will have to look it up) has adapted to pigs.

So, as before: Why do we care? We care for two reasons: First, because since this strain is in a food animal, the possibility exists that it could contaminate the chickens’ meat during slaughter and pass to humans. As has happened with some ST 398, the humans could be only colonized, and not become ill. But, second, any increase in colonization is a bad thing: The more strains out there, the greater the chance that they will exchange virulence and resistance factors and become something unpredictable.

Now, about those layers, here’s an interesting factor that the authors call out in their paper: Layers, unlike broilers, do not receive antibiotics. The layers did not carry MRSA. The broilers did. It’s a pretty potent argument, in case anyone needed convincing, of the effect of the selective pressure that antibiotic use in food animals exerts on these strains.

The site is: Persoons D, Van Hoorebeke S, Hermans K, Butaye P, de Kruif A, Haesebrouck F, et al. Methicillin-resistant Staphylococcus aureus in poultry. Emerg Infect Dis. 2009 Mar; [Epub ahead of print] DOI: 10.3201/eid1503.080696