Public health authorities such as the World Health Organization and industry experts have raised concerns over the thin pipeline of new treatments to tackle antibiotic-resistant bacteria, which they say is not enough to combat the so-called superbugs.

Antimicrobial resistance occurs when bacteria, viruses, fungi and parasites change over time and no longer respond to medicines, making infections harder to treat and increasing the risk of disease spread, severe illness and death.

In the U.S. more than 2.8 million antimicrobial-resistant infections occur each year.