WHO releases a list of pathogens for which new antibiotics are required

The list categorises the bacteria according to the urgency of need for new antibiotics

By Mouna Nagaraju
Published: Tuesday 28 February 2017

It is feared by 2050, antimicrobial resistance will claim 10 million lives globally (Credit: iStock)

The World Health Organization (WHO) on Monday published its first-ever list of antibiotic-resistant "priority pathogens"–12 types of bacteria  that pose the greatest threat to human health.

The list is divided into three categories- priority, high and medium (see box below), according to the urgency of need for new antibiotics. It highlights the threat posed by gram-negative bacteria. Gram negative bacteria do not retain the crystal violet stain used in the Gram staining method of bacterial differentiation.

Priority 1: critical
  • Acinetobacter baumannii, carbapenem-resistant
  • Pseudomonas aeruginosa, carbapenem-resistant
  • Enterobacteriaceae, carbapenem-resistant, ESBL-producing
Priority 2: high
  • Enterococcus faecium, vancomycin-resistant
  • Staphylococcus aureus, methicillin-resistant, vancomycin-intermediate and resistant
  • Helicobacter pylori, clarithromycin-resistant
  • Campylobacter spp., fluoroquinolone-resistant
  • Salmonellae, fluoroquinolone-resistant
  • Neisseria gonorrhoeae, cephalosporin-resistant, fluoroquinolone-resistant
Priority 3: medium
  • Streptococcus pneumoniae, penicillin-non-susceptible
  • Haemophilus influenzae, ampicillin-resistant
  • Shigella spp., fluoroquinolone-resistant

The list includes those bacteria which cause community infections, such as Enterobacteriaceae which includes Escherichia coli and Klebsiella and also healthcare-associated infections, such as Acinetobacter baumannii.  

The pathogens from all three categories are resistant to antibiotics including those termed as ‘critically important for human health’ by WHO such as fluoroquinolones and cephalosporins and those used as ‘last-resort antibiotics’ to treat diseases such as carbapenems. 

The high and medium priority categories contain other increasingly drug-resistant bacteria which cause more common diseases such as gastrointestinal diseases, pneumonia, gonorrhoea and food poisoning caused by salmonella. A recent report which analysed data from 28 member states of the European Union showed high multi-drug resistance (MDR) in salmonella across the EU. Resistance to colistin—a last resort antibiotic—was detected in salmonella and E. coli in pigs and cattle, said the report submitted by European Food Safety Authority and the European Centre for Disease Prevention and Control.

Aim of the list

Drawn up to guide and promote research and development (R&D) of new antibiotics, the list is part of WHO’s efforts to address the growing global resistance to antimicrobial medicines. It is feared by 2050, antimicrobial resistance will claim 10 million lives globally. In India, which is the largest consumer of antibiotics in the world, 461 people per 100,000 die due to infections caused by antimicrobial resistant bacteria, according to a media report.

Dr Marie-Paule Kieny, WHO's Assistant Director-General for Health Systems and Innovation, says, “Antibiotic resistance is growing, and we are fast running out of treatment options. If we leave it to market forces alone, the new antibiotics we most urgently need are not going to be developed in time.”

Criteria for selection

The WHO received a request from member countries to develop a global list of antibiotic resistant bacteria to redirect the focus of development of new antibiotics on these pathogens. The list was developed in collaboration with the Division of Infectious Diseases at the University of Tübingen, Germany, using a multi-criteria analysis technique vetted by international experts. The criteria for selection were: how deadly the infections they cause are; whether their treatment requires long hospital stays; how frequently they are resistant to existing antibiotics when people in communities catch them; how easily they spread between animals, from animals to humans, and from person to person; whether they can be prevented; how many treatment options remain; and whether new antibiotics to treat them are already in the R&D pipeline. For instance, tuberculosis was not included in the list because it is targeted by other, dedicated programmes.

While the development of new antibiotics is required to address the antibiotic resistance, it is equally important to prevent the misuse of antibiotics in humans and in food-animal production and also promote a rational use of new antibiotics developed in future.

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