Antimicrobial resistance (AMR) poses a significant global health threat, hindering the prevention and treatment of infections caused by bacteria, parasites, viruses, and fungi. Antibiotic-resistant pathogens are particularly problematic, leading to increased mortality and healthcare costs. In 2019, antibiotic-resistant infections caused an estimated 1.27 million deaths globally, with the greatest impact on low- and middle-income countries. A 2021 analysis estimated that bacterial AMR was responsible for 4.71 million deaths, including 1.14 million attributable deaths.
In response, the World Health Organization (WHO) launched the Global Action Plan on AMR in 2015 and introduced the Bacterial Priority Pathogens List (BPPL) in 2017 to guide the development of new antibiotics. The BPPL, which identifies 25 antibiotic-resistant pathogens across three priority tiers, has been instrumental in directing research, surveillance, and control efforts. Since then, 13 new antibiotics targeting these pathogens have been approved, and pretomanid has been recommended for treating multidrug-resistant tuberculosis.
Despite progress, AMR continues to evolve with emerging resistance to newer antibiotics. There remains insufficient investment in research, prevention, and control. In response, WHO has updated the BPPL in 2024 to incorporate new data, address the limitations of the 2017 list, and consider the broader public health impact of pathogens, with the goal of informing future AMR research, interventions, and policy.
The 2024 WHO BPPL followed a similar methodology to the initial prioritisation, using a multicriteria decision analysis framework. Twenty-four antibiotic-resistant bacterial pathogens were evaluated based on eight criteria: mortality, non-fatal burden, incidence, 10-year resistance trends, preventability, transmissibility, treatability, and antibacterial pipeline status. Expert judgment and available evidence were used to assess each pathogen on these criteria.
A preferences survey was conducted with 100 international experts (79 respondents, 78 completions) to determine the relative importance of each criterion. The final rankings of pathogens were calculated based on a total score (0–100%) for each pathogen, applying the experts' weighted criteria. Subgroup and sensitivity analyses were performed to examine the consistency and influence of expert backgrounds on the rankings. An independent advisory group reviewed the final list, and the pathogens were then categorised into three priority tiers: critical (highest), high (middle), and medium (lowest), using a quartile scoring system.
The total scores of the pathogens on the 2024 WHO BPPL ranged from 84% for the top-ranked carbapenem-resistant Klebsiella pneumoniae to 28% for the bottom-ranked penicillin-resistant group B streptococci. Antibiotic-resistant Gram-negative bacteria, such as K. pneumoniae, Acinetobacter spp., and Escherichia coli, as well as rifampicin-resistant Mycobacterium tuberculosis, were ranked in the highest quartile. Among bacteria causing community-acquired infections, the highest rankings were for fluoroquinolone-resistant Salmonella enterica serotype Typhi (72%), Shigella spp. (70%), and Neisseria gonorrhoeae (64%). Other notable pathogens included Pseudomonas aeruginosa and Staphylococcus aureus.
The 2024 WHO BPPL highlights the evolving nature of AMR, with updated rankings of bacterial pathogens based on current evidence and expert input. Antibiotic-resistant Gram-negative bacteria remain a critical priority due to their global burden, especially in low-income and middle-income countries, and their complex resistance mechanisms. The WHO emphasises the need for innovative research and development approaches, alongside stronger prevention strategies and equitable access to healthcare, to address these challenges. The list also prioritises community-acquired pathogens, such as rifampicin-resistant Mycobacterium tuberculosis, fluoroquinolone-resistant Salmonella, and Shigella spp., which have risen in importance due to their increasing resistance and burden in resource-limited settings.
Notable changes in the 2024 list include the reclassification of Pseudomonas aeruginosa from critical to high priority and the addition of macrolide-resistant Group A Streptococci, penicillin-resistant Group B Streptococci, and others. The update also acknowledges the need for tailored responses to distinct pathogens, such as third-generation cephalosporin-resistant Enterobacterales. The prioritisation highlights the importance of integrating prevention, vaccination, and improvements in water, sanitation, and hygiene (WASH) alongside the development of new medicines.
The BPPL also calls for more investments in research, including innovative financing mechanisms, and better surveillance systems to address data gaps, especially in low-income regions. Although the list serves as a guide for research and development, it also emphasises the broader need for multisectoral collaboration to combat AMR. Regular updates and continued engagement from all countries, especially low- and middle-income nations, are essential to adapting to the changing landscape of AMR and ensuring equitable access to healthcare.
Source: The Lancet Infectious Diseases
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