WHO “priority pathogens” list: The most dangerous bacteria in the world

Enterobacteriaceae, Acinetobacter baumannii and Pseudomonas aeruginosa (left to right): according to the WHO list the three most dangerous bacteria
Enterobacteriaceae, Acinetobacter baumannii and Pseudomonas aeruginosa (left to right): according to the WHO list the three most dangerous bacteria

As antibiotic-resistant bacteria continue to spread, calls for new therapeutics are getting louder. In response, the World Health Organization (WHO) has drawn up a list of the twelve most important bacteria for which new drugs urgently must be developed. Until then, the current antibiotics should only be used when absolutely necessary. In addition to the list, WHO promotes education and alternative measures to support the rational use of anti-infectives.

When antibiotics are ineffective, doctors are often powerless against the resistant bacteria. In 2017, the worrying case of an American pensioner in Nevada became known: She died of an infection caused by a multi-resistant Klebsiella pneumoniae bacteria after none of the 26 approved antibiotics had worked.

The death of the American patient is a drastic illustration of a global problem. Taking Germany as one example, “approximately 30,000 to 35,000 patients develop nosocomial infections caused by multidrug resistant organisms (MDRO),” as Petra Gastmeier, head of the German National Reference Centre for Surveillance of Nosocomial Infections, and colleagues explain in the German Medical Journal. Currently, no robust data exist on how many patients in Germany die each year as a result of MDRO infections.“ According to the best available estimate, the annual number may be between 1,000 and 4,000 cases.” This is about 3 to 13 per cent of all infections with a multi-resistant pathogen.

That is why the WHO has stepped up the fight against antimicrobial resistance. Above all, it wants to create incentives for researchers at universities and pharmaceutical companies to develop new drugs. According to a statement, the intention is to “focus research efforts” by offering incentives such as premiums for launching new drugs on the market, for example.

WHO experts, along with researchers from the University of Tübingen have published a global priority pathogens list of bacteria that pose a particular risk to human health – and for which new drugs urgently need to be developed. Bacteria that are resistant to several antibiotics represent the greatest threat. The list is divided into three groups with different priorities (see below).

3 groups with different priorities

According to the WHO, the highest priority must be placed on the first group of bacteria. This critical category includes Acinetobacter baumannii and Pseudomonas aeruginosa, both of which can cause wound infections, and the group of Enterobacteriaceae. Enterobacteria include Klebsiella, E. coli, Serratia and Proteus. All of these bacteria are resistant to carbapenems (“carbapenem-resistant”). Doctors currently used this class of antibiotics only when other antibiotics are no longer effective.

The second group has high priority, and includes, for example, Enterococcus faecium, Staphylococcus aureus and Campylobacter. These bacteria are resistant to various antibiotics, such as vancomycin, fluoroquinolones or methicillin.

The third group has medium priority. It includes Streptococcus pneumoniae and Shigella. Resistance occurs in these germs; however, effective antibiotics exist that can kill these bacteria.

An equally important aspect in reducing the spread of antibiotic-resistant bacteria is implementing infection control measures, according to WHO researchers. They recommend a programme that focuses on improving and standardising such measures. Such a programme could possibly lead to more consistent application across the WHO regions.

The complete WHO priority pathogens list

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

Further information

  1. WHO publishes list of bacteria for which new antibiotics are urgently needed, World Health Organization

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