Resistant E. coli can make a UTI deadly Erbe/Pooley/REX/Shutterstock

For the first time, the World Health Organization has named which bacteria we most urgently need new antibiotics to fight, as they become increasingly resistant to the ones we’ve already got. Top of the list are gut bacteria such as Escherichia coli – a deadly threat in hospitals, but also the leading cause of urinary tract infections, which affect an estimated 250 million people a year, most of them women.

The WHO’s list is aimed at a G20 meeting in Berlin, Germany, at which the world’s twenty richest countries will discuss how to pay pharmaceutical companies to develop new antibiotics, which are otherwise too unprofitable to invest in. Priorities need to be spelled out, says Nicola Magrini of the WHO, partly because what work is being done on new antibiotics is largely aimed at the bacteria for which it is easiest to find and test new drugs, not those doing the most damage.

Researchers at the WHO and at the University of Tübingen, Germany, pinpointed the most damaging families of drug-resistant bacteria based on criteria such as how often bacteria resist antibiotics, how many they resist, how often they kill, and the numbers of people affected.


The most crying need is for drugs to kill Acinetobacter, Pseudomonas, and members of the Enterobacteria family that resist the last-resort carbapenem antibiotics. The Enterobacteria include E. coli, which takes a heavy toll in hospitals and nursing homes, where it causes blood and lung infections that are often fatal.

E. coli is also the cause of most UTIs, one of the most common infections that require treatment with antibiotics – half of all women have a UTI at least once in their lives. Functioning antibiotics make UTIs only a minor annoyance, but if antibiotics fail, the infection can spread into the kidneys and bloodstream, and even become life-threatening. UTIs that resist one or more types of antibiotic are becoming more common.

“There are few options for treating a UTI due to extensively drug resistant bacteria,” says Abdul Ghafur at the Apollo Specialty Hospital in Chennai, India, a leading expert on antibiotic resistance. “In severe cases we may have to use intravenous colistin, but colistin resistance is increasingly being reported in India.” UTIs resistant to all antibiotics “do occur.”

Neglected by research

Of the most worrying bacteria named by WHO, 9 out of 12 families are of the “gram-negative” type, which are especially neglected in current research, says Magrini.

After the top three threats – all of which are gram-negative – come Enterococcus and Staphylococcus strains that resist another last-resort drug, vancomycin; the stomach ulcer bug, Heliocobacter; the two most common causes of food poisoning, Salmonella and Campylobacter; and gonorrhoea, which is becoming untreatable. Only slightly less threatening are drug-resistant Streptococcus, Shigella, and Haemophilus influenzae.

The colistin resistance that could make UTIs untreatable is thought to have arisen as a result of using large amounts of the drug as a growth promoter in livestock. Marie-Paule Kieny, head of Health Systems and Innovation at the WHO, stresses that preventing antibiotic resistance through proper use of existing drugs is still vital – but we also really need to invent some new ones.

Read more: Antibiotics apocalypse: Tales from fighters on the front line