Maryn McKenna

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Does ethanol production produce resistant bacteria too?

April 22, 2009 By Maryn 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.

Filed Under: animals, antibiotics, E.coli, Europe, food, veterinary, VRE

Bad news from Australia: MRSA in water supplies

February 24, 2009 By Maryn Leave a Comment

The Brisbane Courier-Mail reports that scientists in Australia have found MRSA and VRE from hospital sewage in rivers and lakes throughout the state of Queensland, and have been trying for two years to get their provincial government to pay attention.

Secret tests on waste water discharged from 28 Queensland hospitals and clinics revealed the widespread presence of MRSA (Methicillin resistant Staphylococcus aureus) and VRE (Vancomycin resistant Enterococci).
However there was no evidence the potentially lethal organisms had made their way into drinking water.
A Central Queensland University scientist who helped carry out the research told me 97 per cent of hospital sewage discharge lines tested positive for antibiotic resistant bacteria.
He said 70 per cent of hospital discharges tested positive for both MRSA and VRE.
“We got a lot more of those bacteria than we thought possible,” he said. … “Even though they have passed through a treatment process, the bacteria are most likely getting back into natural waterways, dams and ponds used for swimming, boating, fishing and in food production.” (Byline: Des Houghton)

The report was presented to the Queensland parliament by a member in 2007, ignored, and presented again last week. (Note for US readers who click through to the story, from my UK childhood: “Tabled,” in parliamentary parlance, means “brought forward” or “introduced” — not “postponed” as we would interpret it.)

The wastewater was treated in a sewage plant and then tested — but the usual tests look for enteric pathogens such as E. coli, not for MRSA, so the water passed testing without MRSA’s presence being detected.

There have been similar studies in Portugal, South Africa and Nigeria. In the US, MRSA and other resistant bacteria have been found in groundwater and airborne dust, but that has been due to leakage from industrial farming. I’m not aware of anyone doing this sort of study, with organisms escaping from hospitals, in this country. If anyone does know of one, and has a cite, please comment!

Filed Under: animals, antibiotics, environmental, MRSA, VRE

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