A new online campaign is putting pressure on fast food giant McDonald's to impose a global ban on products from animals treated with antibiotics.
Scientists warn that treating livestock with antibiotics is leading to a rise in drug-resistant superbugs.
The charity ShareAction has called on consumers to email McDonald's chief executive Steve Easterbrook.
Last week, the fast food chain stopped using poultry treated with antibiotics - but only in its US restaurants.
ShareAction has called on McDonald's - which operates in more than 100 countries - to stop using chicken, beef, pork and dairy products that have been given antibiotics in all of its 30,000 stores globally.
'Superbugs'
Medical experts warn that the routine use of antibiotics to promote growth and prevent - rather than treat - illness in farm animals contributes to the rise of drug-resistant "superbug" infections. They are said to kill at least 23,000 Americans a year and represent a significant threat to global public health.
Scientists have warned the world is on the cusp of the "post-antibiotic era" after discovering in China in November 2015 bacteria resistant to the antibiotic colistin - the medication used when all others have failed.
It appeared to develop in farm animals before also being detected in hospital patients.

Fast food restaurants have become a focal point for change in the food industry by forcing suppliers to change their practices.
According to ShareAction, more than 70% of all antibiotics used in the US are given to livestock.
'Supersize their ambition'
In the UK, that figure stands at more than 50% according to the group.
"We hope this action will encourage McDonald's to supersize their ambition," said ShareAction chief executive Catherine Howarth.
McDonald's told the Reuters news agency that it was too early to set a timeline for phasing out the use of all meat and milk products from animals treated with antibiotics.
The company cited varying practices and regulations around the world as one of the difficulties, but added that it "continues to regularly review this issue".

Rival fast food groups are also under pressure to take action.
On Thursday KFC was the target of a petition from consumer groups that called on the chicken chain to stop using poultry products treated with antibiotics.
KFC has already said it will limit the use of human antibiotics in its chicken by next year.
However, critics claim the policy still allows for routine use of antibiotics by its chicken suppliers.
US burger chain Wendy's plans to stop using chickens raised with antibiotics by 2017 and also plans to set similar goals for pork and beef.
Antibiotics - what you need to know
Some infections are becoming almost impossible to treat because of the excessive use of antibiotics.
More than half of the antibiotics used around the world are used in animals, often to make them grow more quickly.
Scientists warned the world was on the cusp of the "post-antibiotic era" after discovering in China in November 2015 bacteria resistant to the antibiotic colistin - the medication used when all others have failed.
It appeared to develop in farm animals before also being detected in hospital patients.
In some cases, antibiotics are used in agriculture to treat infections - but most are used prophylactically in healthy animals to prevent infection or, controversially, as a way of boosting weight gain.
Using antibiotics as growth promoters was banned in the EU in 2006.
Such uses are more common in intensive farming conditions.
Antibiotics are most useful in cramped dirty conditions where infections are easier to spread, so more spacious and hygienic living conditions are one way to reduce the need for antibiotics.
There are also calls for greater investment in research for vaccines and for tests that can diagnose specific infections and a call for countries to agree on a banned list of antibiotics that would never be used in animals, because of their importance to human health.

Published Date:2016-08-13