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Undercooked turkeys can harbour superbugs

 

NewScientist.com news service

Andy Coghlan

An in-depth analysis of bacteria in US turkeys has revealed that high

proportions of bacteria found in the birds 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, 194 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 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)

 

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