LOS ANGELES (Reuters) - Yum Brands Inc's YUM.N U.S. KFC chain plans to curb the use of antibiotics in its chicken supply, making it the last of the big three chicken restaurants to join the fight against the rise of dangerous antibiotic-resistant bacteria known as superbugs.

A Kentucky Fried Chicken bucket of mixed fried and grilled chicken. REUTERS/Carlo Allegri

KFC, the second-biggest U.S. chicken chain by sales after privately held Chick-fil-A, is giving its U.S. poultry suppliers until the end of 2018 to stop using antibiotics important to human medicine.

Some 70 percent of antibiotics vital for fighting infections in humans are sold for use in meat and dairy production and medical researchers have concerns that overuse of those drugs may diminish their effectiveness in fighting disease in humans.

McDonald's Corp's MCD.N roughly 14,000 U.S. restaurants last year stopped serving chicken raised with antibiotics considered important to human medicine. Its Chicken McNuggets are a top seller and the change put pressure on the rest of the industry to follow.

Chick-fil-A is going a step further, vowing in 2014 to switch to poultry raised without any antibiotics at all by the end of 2019.

Given its stature, KFC had been the focus of several antibiotic reduction campaigns by consumer, health and environment groups in addition to a coalition of British and U.S. shareholders with more than $2 trillion in assets under management.

“We recognize that it’s a growing public health concern,” KFC U.S. President Kevin Hochman told Reuters on Thursday.

“This is something that’s important to many of our customers and it’s something we need to do to show relevance and modernity within our brand,” Hochman said.

The policy applies only to KFC in the United States and its 4,200 restaurants supplied by some 2,000 domestic chicken farms, said Hochman. KFC’s antibiotic policy is set on a country-by-country basis, he added. Yum spun off its KFC-dominated China division in November.

‘GREAT NEWS FOR FRIED CHICKEN LOVERS’

Vijay Sukumar, chief food innovation officer for KFC U.S., said the new policy applies throughout the bird’s full life cycle, which includes the hatchery where chicks are sometimes injected with antibiotics while still in the shell.

Using data from a 2017 WATT PoultryUSA survey, the Natural Resources Defense Council (NRDC) estimates that more than 42 percent of the U.S. chicken industry is either under an antibiotics stewardship pledge or has already converted to responsible practices.

KFC's new policy will likely move the number even higher, said Lena Brook, a food policy advocate at the NRDC, who noted that the estimate includes "raised without antibiotics" pledges as well as "raised without medically important" antibiotics pledges from producers like Tyson Foods Inc TSN.N, Perdue Farms and others.

Slideshow ( 3 images )

“It’s great news for fried chicken lovers, and most importantly it’s great news for public health,” Brook said. “Their commitment is one that we’ve been waiting for.”

Human infections from antibiotic-resistant bacteria pose a grave threat to global health and are estimated to kill at least 23,000 Americans each year, although a recent Reuters investigation found that many infection-related deaths are going uncounted.

Hochman said the policy change has been in the works for a year. It will add some incremental cost that KFC plans to manage rather than pass on in the form of menu price increases, he said.

At least some of KFC suppliers are already well on their way to compliance.

Tyson, the largest U.S. poultry producer and a KFC supplier, has announced plans to eliminate the use of human antibiotics in its chicken flocks by September 2017.

Yum’s Taco Bell chain already committed to serve chicken raised without antibiotics important to human medicine in all U.S. restaurants by the end of last month. Its Pizza Hut division has the same rules for pizza toppings.