Food poisoning bacteria focus

- Last updated on GMT

Related tags: Campylobacter, Antibiotic resistance

More than 40 per cent of bacteria found in chicken on sale in
Switzerland is resistant to at least one antibiotic, say
researchers publishing their findings this week in BMC Public
Health. The results could have wider implications for treating food

The bacteria, Campylobacter​, causes between 5 and 14 per cent of all diarrhoeal illness worldwide and in Switzerland, 1 in 1,086 people suffer from a Campylobacter​ infection every year. The most common sources of infection are inadequately cooked meat, particularly poultry, unpasteurised milk and contaminated drinking water.

Although the illness normally clears up after a week without treatment, small children and people with a weakened immune system often take antibiotics to prevent the infection from spreading to the bloodstream - and causing life threatening septicaemia.

Researchers from the Swiss Federal Veterinary Office collected raw poultry meat samples from 122 retail outlets across Switzerland and Liechtenstein, and tested their antibiotic resistance. From 415 meat samples, they isolated 91 strains of Campylobacter, 59 per cent of which were sensitive to all the antibiotics tested.

According to the results​19 strains - 22 per cent - were resistant to one antibiotic, 9 strains - 10 per cent - to two antibiotics, and 8 strains - 9 per cent - were resistant to at least three antibiotics. Two strains were resistant to five antibiotics. One of these showed resistance to ciprofloxacin, tetracycline and erythromycin - the most important antibiotics for treating Campylobacter​ infection in humans.

Meat was more likely to be infected with Campylobacter if it was kept chilled, rather than frozen. However, the storage conditions did not affect the frequency of antibiotic resistance in the bacteria, report the scientists.

Although the frequency of antibiotic resistance in Switzerland may seem high, meat produced in the country was, in fact, less likely to be infected with antibiotic resistant Campylobacter than meat produced elsewhere, claim the researchers.

"The level of antibiotic resistance in Campylobacter depends on the amount of antibiotics that the chickens received. Maybe in Switzerland antibiotics were used less, so there is less resistance,"​ said one of the researchers involved in the project Jürg Danuser.

Initially, the researchers thought that poultry was more likely to be infected with antibiotic resistant bacteria if it was raised using conventional indoor farming methods rather than in an 'animal-friendly' way.

But they report that the majority of meat produced in an 'animal friendly' way came from Switzerland, which skewed the results. They concluded that only the country of origin, and not the farming methods, were likely to influence the level of antibiotic resistance in the bacteria.

"It's possible that chickens raised in an animal-friendly way are more healthy, so they need less treatment with antibiotics and so their Campylobacter are less resistant to antibiotics. But the other side of the story is that these chickens go outside more often, so they are in more contact with wild birds, which is the reservoir of Campylobacter,"​ commented Danuser.

Although the findings are of some concern for Swiss consumers, the researchers claim that the picture for other countries is even bleaker.

"The high prevalence of Campylobacter in raw poultry meat samples found in this study agrees with data from other studies,"​ they said. In the US, 90 per cent of Campylobacter​ strains isolated from poultry meat had resistance to at least one, and 45 per cent to at least two antibiotics, commented the researchers.

Worries over antibiotic resistant bacteria led the EU, in 1999, to ban the use of four antibiotics as growth promoters in chickens. The US Food and Drugs administration (FDA) followed their lead in late 2000 by banning the use of a particular class of antibiotics called fluorquinolones in poultry farming.

Related topics: Science, Food Safety & Quality

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