- High proportions of bacteria found in US turkeys are
"superbugs", resistant to many of the antibiotics used on farms
and to treat people.
-
- The study sampled over 1000 turkey carcasses from two
undisclosed turkey-processing plants in the US Midwest. Of these, 94 birds
"were found to contain strains of both Campylobacter and Salmonella",
says Catherine Logue, head of the team at North Dakota State University
in Fargo, US, which conducted the study.
-
- It is well established that commercial poultry - including
turkeys - can contain bacteria that cause serious gastrointestinal upsets
if it is not cooked properly. But this latest finding raises the possibility
that antibiotic-resistant bacteria might find their way from turkeys into
the human food chain, and possibly into hospitals.
-
- Each year, Campylobacter and Salmonella make 2 to 4 million
US citizens ill, and could prove much more difficult to treat if they become
resistant to clinical antibiotics, such as erythromycin, ciprofloxacin,
gentamicin and tetracycline.
-
- Gene scavenging
-
- Of the Salmonella samples grown from the infected birds,
many were resistant to several antibiotics - 88% of Salmonella samples
from one plant were resistant to tetracycline, and 35% from the other.
Around 45% of the samples from one plant were simultaneously resistant
to four antibiotics.
-
- Logue says that resistance in Salmonella may be so abundant
because 68% of the strains her team grew had genes for making class I integrase.
This enzyme enables bacteria to scavenge "cassettes" of genes
that confer resistance to antibiotics, either from the environment or from
other bacteria.
-
- Of the Campylobacter samples, 58% from one processing-plant
were resistant to at least one antibiotic, while more than 10% of samples
from the other plant were resistant to no less than 8 antimicrobials.
-
- Although no Campylobacter had the class I integrase gene,
more than a third had "efflux pump" genes which enable bacterial
cells to survive by ejecting antibiotics.
-
- Faster fattening
-
- Logue says that the scale of the risks posed by resistant
bacteria in turkeys is difficult to assess. In a previous study by her
group published in 2003, she found that around 17% of processed birds were
infected with Salmonella, while a parallel study found that 35% of birds
carried Campylobacter.
-
- Antibiotics have been routinely given to turkeys to fatten
them up faster and keep them healthy. But this practice pushes the bacteria
to evolve resistance to the farmyard antibiotics, and also to related drugs
used in human medicine.
-
- Europe banned a group of antibiotic growth promoters
a decade ago to try to curb the rise of resistance. The US Food and Drug
Administration is worried too, and in March 2004 upheld a 2000 decision
to stop farmers giving poultry enrofloxicin, an antibiotic similar to the
medically important fluoroquinolohe medically important fluoroquinolones.
-
- Whatever the risk that resistant bacteria will spread
from turkey farms to people to hospitals, Logue says that turkey is safe
to eat provided it is thoroughly cooked. "Just make sure it's thoroughly
de-frosted, and that you cook it right through, all the way to the core,"
she says.
-
- Journal reference: Food Microbiology (vol 21, p779)
-
- http://www.newscientist.com/article.ns?id=dn6820
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