WHO Updates List of Most Dangerous Drug-Resistant Bacteria for 2024

New Guidance Aims to Combat Rising Threat of Antimicrobial Resistance with Updated Bacterial Priority Pathogens List.

The World Health Organization (WHO) has updated its list of the most dangerous antibiotic-resistant bacteria in 2024, highlighting 15 families of bacteria that pose the biggest threat to human health. These bacteria are divided into critical, high, and medium priority groups. The list aims to guide the development of new treatments to combat antimicrobial resistance (AMR).

AMR happens when bacteria, viruses, fungi, and parasites no longer respond to medicines, making infections harder to treat and increasing the risk of disease spread, severe illness, and death. This resistance is mainly caused by the misuse and overuse of antimicrobials. The updated list incorporates new evidence and expert opinions to direct research and development for new antibiotics and promote international cooperation to spur innovation.

Dr. Yukiko Nakatani, WHO’s Assistant Director-General for Antimicrobial Resistance, said that the list helps identify the most significant drug-resistant bacteria and assess their impact on public health. Since the first list in 2017, the threat of AMR has worsened, reducing the effectiveness of many antibiotics and threatening modern medical advances.

Critical priority pathogens include gram-negative bacteria resistant to last-resort antibiotics and Mycobacterium tuberculosis resistant to rifampicin. These bacteria are highly dangerous because they are difficult to treat and can transfer resistance to other bacteria. Gram-negative bacteria are particularly concerning as they can easily develop new ways to resist treatment and spread these abilities to other bacteria.

High priority pathogens, such as Salmonella, Shigella, Pseudomonas aeruginosa, and Staphylococcus aureus, are especially problematic in low- and middle-income countries and healthcare settings. Other high priority bacteria, like antibiotic-resistant Neisseria gonorrhoeae and Enterococcus faecium, cause persistent infections and resist multiple antibiotics, necessitating targeted research and interventions.

Medium priority pathogens include Group A and B Streptococci, Streptococcus pneumoniae, and Haemophilus influenzae. These bacteria pose a high disease burden and need more attention, especially for vulnerable populations like children and the elderly in resource-limited areas.

Dr. Jérôme Salomon, WHO’s Assistant Director-General for Universal Health Coverage, emphasized that AMR threatens the ability to treat common infections like tuberculosis, leading to severe illness and higher death rates. The updated list also underscores the need for universal access to quality and affordable prevention, diagnosis, and treatment of infections.

The 2024 list reflects changes from the 2017 list, removing five pathogen-antibiotic combinations and adding four new ones. For instance, third-generation cephalosporin-resistant Enterobacterales are now listed as a standalone critical priority due to their significant burden, particularly in low- and middle-income countries. Carbapenem-resistant Pseudomonas aeruginosa has moved from critical to high priority due to recent decreases in global resistance, though continued investment in research and prevention is necessary.

The updated list includes the following bacteria:

Critical priority:

  • Acinetobacter baumannii, carbapenem-resistant
  • Enterobacterales, third-generation cephalosporin-resistant
  • Enterobacterales, carbapenem-resistant
  • Mycobacterium tuberculosis, rifampicin-resistant

High priority:

  • Salmonella Typhi, fluoroquinolone-resistant
  • Shigella spp., fluoroquinolone-resistant
  • Enterococcus faecium, vancomycin-resistant
  • Pseudomonas aeruginosa, carbapenem-resistant
  • Non-typhoidal Salmonella, fluoroquinolone-resistant
  • Neisseria gonorrhoeae, third-generation cephalosporin- and/or fluoroquinolone-resistant
  • Staphylococcus aureus, methicillin-resistant

Medium priority:

  • Group A streptococci, macrolide-resistant
  • Streptococcus pneumoniae, macrolide-resistant
  • Haemophilus influenzae, ampicillin-resistant
  • Group B streptococci, penicillin-resistant

These changes highlight the dynamic nature of AMR and the need for targeted interventions. Adapting the list to specific country and regional contexts can help address variations in pathogen distribution and AMR burden. For example, antibiotic-resistant Mycoplasma genitalium, not included in the list, is becoming a growing concern in some regions.

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