The drugs, designed to keep the birds healthy and promote growth, are largely ineffective, Otago University scientists have found.

Researchers studied bacteria in chicken guts and found 99 per cent of the bacterium Enterococcus faecalis was resistant to specific antibiotics commonly used in New Zealand and overseas.

Now the team is trying to design a new drug to help combat the resistance. If successful, it could eventually be used with antibiotics to improve their effectiveness.

However, lead researcher, Associate Professor Greg Cook, said it would be better if the poultry industry did not use huge quantities of antibiotics.

Quantities have been steadily increasing over the past decade to more than 26,000kg annually.

"If 99% of the bacteria is resistant to it (the antibiotic), the question is, `why are we feeding it to poultry?' They are too scared to stop feeding it in case they (the chickens) all get sick and die," Cook said yesterday.

Green Party health spokeswoman Sue Kedgley said the high level of antibiotics use was a big concern.

Source: Stuff