SAO PAULO (Reuters) - Pork products sold at retailers in Brazil contain antibiotic-resistant bacteria, according to a study funded by animal rights group World Animal Protection (WAP), providing potential evidence of overuse of the medicines in food livestock.

The study, which also looked at pork in three other countries, was conducted by the University of São Paulo on behalf of WAP in Brazil. It examined 100 meat samples from outlets owned by Carrefour, GPA and Walmart, WAP said.

“In all of the samples, the tests detected a generalized presence of bacteria resistant to antibiotics,” WPA noted in a report last week describing the study’s findings.

Researcher Terezina Knobl told Reuters on Monday that the issue related to super-resistant bacteria is global and addressing it is one of five priorities of the World Health Organization.

Still, she noted consumers need not be alarmed as there is no immediate risk of death or disease related to meat consumption.

“One of the aims of the study is advocating for a more rational use of antibiotics in livestock production,” Knobl said.

As antibiotics are overused both in people and to prevent disease in livestock, the fear is that bacteria will develop resistance to all available treatments for when they are truly needed.

“Beyond treating disease, the antibiotics are commonly used to avoid illnesses caused by the handling of the animals and the high levels of stress caused by the extreme conditions in which they are confined,” WAP said.

According to the BMC Veterinary Research journal, antimicrobial resistance is a public health threat worldwide. There are at least two million resistant infections and at least 23,000 related deaths in the United States each year, its research showed.

The rise of resistant bacteria may lead to a clamp-down on overuse of antimicrobial drugs in Brazil, the world’s fourth largest pork producer and exporter, and elsewhere.

U.S. livestock consumes 70 percent of all antibiotics, according to a 2014 Britain-commissioned Review on Antimicrobial Resistance.

Earlier this month, McDonald’s Corp said it would take steps to curb use of antibiotics in its global beef supply.

Brazil’s unit of Carrefour said it is working with WAP to improve animal well-being policies. GPA said it only sells meat products inspected by the Agriculture Ministry. Walmart did not immediately reply to a request for comment.

“There can be no pork production without antibiotics,” said Brazilian pig farmer Wilant Boogaard, arguing that vaccines and antibiotics are needed to prevent and treat disease.