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On the trail of drug-resistant salmonella
August 5th, 2011
11:13 AM ET

On the trail of drug-resistant salmonella

Newer technologies offer a tremendous opportunity to track the development of highly dangerous bacteria, but tough economies and budget cuts threaten to choke off that promise, according to a pair of articles in the "Journal of Infectious Disease."

One paper by researchers from several European countries traced the gradual spread of a drug-resistant version of a salmonella strain known as S. enterica serotype Kentucky. According to Craig Hedberg, an environmental health scientist with the University of Minnesota School of Public Health, says the normal Kentucky strain does not often cause human illness. It mostly circulates, uneventfully, in poultry, without harming the birds.

About a decade ago, genetic analysis of samples from France, England and Wales, Denmark and the United States began to pick up a variant that’s resistant to powerful antibiotics, including ciproflaxin, or Cipro. Many of the samples came from human patients, who became seriously ill from the new strain. In 2002, it was rare, with just three human cases. By 2008, there were 489 confirmed human cases.

As Hedberg wrote in an editorial that accompanied the article, “the multi-drug resistant clone of S. Kentucky could be a major public health threat.”

This version of S. Kentucky is not the only strain of antibiotic-resistant salmonella. One well-known version is known as Salmonella Typhimurium DT104. Meanwhile, the salmonella that has sickened at least 78 people and led to a nationwide recall of ground turkey, can be treated with Cipro but is resistant to several other common antibiotics, according to the Centers for Disease Control and Prevention.

Chickens and turkeys have adapted to live with salmonella, which rarely makes the birds sick. Based on testing at U.S. poultry facilities, about 10 percent of the birds carry salmonella bacteria. Phyllis Entis, a microbiologist who spent seven years working on food safety for Canada’s federal government, and who now writes a blog on food safety issues, says the U.S. lags far behind Scandinavian countries in controlling salmonella in the food supply. Entis says that Denmark, whose data were featured in the S. Kentucky paper, does frequent tests for salmonella and does not allow infected poultry to enter the food system, even if it’s not associated with an outbreak.

“It is possible to do, and it can be done, with proper culling of infected flocks,” she said.

Al Yancy, Vice-President of Food Safety and Poultry Production programs for the U.S. Poultry and Egg Association, says such caution is unnecessary. “To condemn raw poultry simply because it tested positive for a ubiquitous organism, you might even say is morally and ethically untenable,” Yancy told CNN. “With raw chicken [or turkey], the aim is to be as safe as possible, but safe shouldn’t be defined as ‘no salmonella.’ This meat can be rendered safe by cooking and proper handling.”

According to Entis, the biggest factor in producing resistant bacteria is the use of antibiotics in poultry feed. That view was echoed in congressional testimony in 2009 by Joshua Sharfstein, deputy commissioner of the  Food and Drug Administration. At the time, Sharfstein said there is “clear evidence” that the use of antibiotics to promote growth in animals, encourages drug resistance. “Purposes other than for the advancement of animal or human health should not be considered judicious use.”

Yancy acknowledges widespread use of antibiotics by poultry producers, but says members of his organization – “the world’s largest trade association representing feathered species” – follow guidelines set by the American Veterinary Medicine Association, which call for antibiotic use to be limited where possible.

The article in the Journal of Infectious Disease says it appears the spread of drug-resistant S. Kentucky is associated with poultry, but says that can’t be confirmed without better surveillance data from poultry operations. He authors say it’s possible the strain was also spread through aquaculture – fish farming – especially on farms where poultry products were used to fertilize ponds, or where waste from the fish farms was used as a supplement in feed for the birds.

“This paper demonstrates both the opportunities and the challenges of doing this kind of surveillance,” Hedberg told CNN. “We need to take maximum advantage of surveillance systems, to get an early indicator of where problems are developing."

However, he said the strategies of regular surveillance and testing are threatened by budget cuts in Europe and the United States.  “Support for many public health activities, including primary and secondary prevention measures, such as public health surveillance, is considered discretionary,” he wrote in his editorial. “Therefore, cutting these funds does not appear to result in a direct and measurable harm.”

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soundoff (5 Responses)
  1. Burbank

    All due to agribusiness. I remember the days when it was safe to eat your eggs over easy or even sunny side up. Not anymore! Root cause? Overpopulation. If we werent' overpopulated greedy agribusiness farming with closely caged animals forced to live on top of their own excrement would not be necessary.

    August 5, 2011 at 17:04 | Report abuse | Reply
  2. Larry

    We need to keep accepting these weak crippled birds in our grocery stores because agribusiness tells us they are okay to eat. Raising healthy birds would cost too much. People want cheap food. With enough salt, sugar and fat in the mix people will eat lots of non food items and come back for more. Until people change their eating habits nothing will change.

    August 6, 2011 at 10:43 | Report abuse | Reply
  3. Leslie

    Just raise your own chicken and turkey. Its not hard, tastes better,and is quite a bit healther for you in the long run. You are in control of what you put into your meat.

    August 7, 2011 at 05:31 | Report abuse | Reply
    • Tom, Tom, the Piper's Son

      Leslie, you're simply making an absurd statement. Are you living in Idaho? Arkansas? People who live in cities and suburbs are not able to "raise (their) own chicken and turkey", you moron.

      August 7, 2011 at 17:53 | Report abuse |
  4. skeptic

    The "trail" of data in one of the articles (PMID: 21813512) ends in 2008. I still have to see any epidemiological data on Kentucky since 2008/2009 to be convinced by what I see now as typical alarmist response of the media on random peer-reviewed article...

    August 8, 2011 at 06:40 | Report abuse | Reply

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