The World Health Organisation (WHO) has announced its first list of antibiotic-resistant "priority pathogens" on 27 February, detailing 12 families of bacteria that experts say pose the greatest threat to human health and is the cause of death for millions of people every year.

The list has divided into three categories -critical, high and medium priority - based on the urgency of the need for new antibiotics. It was formed to guide and promote research and development of new drugs, officials said.

Top of the list are many gram-negative bugs that are resistant to multiple antibiotics, such as Acinetobacter, Pseudomonas and various Enterobacteriaceae, which can cause lethal bloodstream infections and pneumonia in frail hospital patients. The list will be discussed ahead of the G20 meeting in Germany this July.

List based on careful deliberation of many factors

"We are fast running out of treatment options," said Dr Marie-Paule Kieny, WHO's assistant director-general, "If we leave it to market forces alone, the new antibiotics we most urgently need are not going to be developed in time."

She added that antibiotic resistance was reaching "alarming proportions" and yet the pipeline was "practically dry". 

WHO listed the superbugs with critical priority as those responsible for severe infections and high mortality rates, especially among hospitalised patients in intensive care or using ventilators and blood catheters, as well as among transplant recipients and patients undergoing chemotherapy.

The list was drawn up in collaboration with the Division of Infectious Diseases at the University of Tübingen, Germany, based on the current level of drug resistance, length of hospital stays, global death rates, prevalence of the infections in communities, burden the diseases cause on health systems, and the transmission rates between animals, animals to humans and person to person.

Tuberculosis was not included as the search for new treatments has already been prioritised by other dedicated programs.

Addressing the superbug problem from all angles

Public health experts welcomed the announcement, especially the need to address the problem in a broad manner. The agency emphasised that the current focus should be on clinical need instead, warning pharmaceutical companies not to develop only treatments that are easier and more profitable to make.

"We cannot just discover and develop our way out of this crisis," said Helen Boucher, an infectious diseases doctor at Tufts University and a spokeswoman for the Infectious Diseases Society of America. Other methods such as prevention, appropriate use of antibiotics and surveillance are all necessary as part of a coordinated approach, she added.

Recently, the US reported a fatal case of a woman who was infected with carbapenem-resistant Klebsiella bacterium, and could not be treated with 26 different antibiotics, alarming health experts globally. MIMS

Here is the list from WHO:

Priority 1: Critical
1. Acinetobacter baumannii, carbapenem-resistant
2. Pseudomonas aeruginosa, carbapenem-resistant
3. Enterobacteriaceae, carbapenem-resistant, ESBL-producing

Priority 2: High
4. Enterococcus faecium, vancomycin-resistant
5. Staphylococcus aureus, methicillin-resistant, vancomycin-intermediate and resistant
6. Helicobacter pylori, clarithromycin-resistant
7. Campylobacter spp., fluoroquinolone-resistant
8. Salmonellae, fluoroquinolone-resistant
9. Neisseria gonorrhoeae, cephalosporin-resistant, fluoroquinolone-resistant

Priority 3: Medium
10. Streptococcus pneumoniae, penicillin-non-susceptible
11. Haemophilus influenzae, ampicillin-resistant
12. Shigella spp., fluoroquinolone-resistant

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