The WHO Bacterial Priority Pathogens List 2024: a prioritisation study to guide research, development, and public health strategies against antimicrobial resistance
Hatim Sati, Elena Carrara, Alessia Savoldi, et al
Lancet Infect Dis 2025 https://doi.org/10.1016/S1473-3099(25)00118-5
Summary
Background
The 2017 WHO Bacterial Priority Pathogens List (BPPL) has been instrumental in guiding global policy, research and development, and investments to address the most urgent threats from antibiotic-resistant pathogens, and it is a key public health tool for the prevention and control of antimicrobial resistance (AMR). Since its release, at least 13 new antibiotics targeting bacterial priority pathogens have been approved. The 2024 WHO BPPL aims to refine and build on the previous list by incorporating new data and evidence, addressing previous limitations, and improving pathogen prioritisation to better guide global efforts in combating AMR.
Methods
The 2024 WHO BPPL followed a similar approach to the first prioritisation exercise, using a multicriteria decision analysis framework. 24 antibiotic-resistant bacterial pathogens were scored based on eight criteria, including mortality, non-fatal burden, incidence, 10-year resistance trends, preventability, transmissibility, treatability, and antibacterial pipeline status. Pathogens were assessed on each of the criteria on the basis of available evidence and expert judgement. A preferences survey using a pairwise comparison was administered to 100 international experts (among whom 79 responded and 78 completed the survey) to determine the relative weights of the criteria. Applying these weights, the final ranking of pathogens was determined by calculating a total score in the range of 0–100% for each pathogen. Subgroup and sensitivity analyses were conducted to assess the impact of experts’ consistency, background, and geographical origin on the stability of the rankings. An independent advisory group reviewed the final list, and pathogens were subsequently streamlined and grouped into three priority tiers based on a quartile scoring system: critical (highest quartile), high (middle quartiles), and medium (lowest quartile).
Findings
The pathogens’ total scores ranged from 84% for the top-ranked bacterium (carbapenem-resistant Klebsiella pneumoniae) to 28% for the bottom-ranked bacterium (penicillin-resistant group B streptococci). Antibiotic-resistant Gram-negative bacteria (including K pneumoniae, Acinetobacter spp, and Escherichia coli), as well as rifampicin-resistant Mycobacterium tuberculosis, were ranked in the highest quartile. Among the bacteria commonly responsible for community-acquired infections, the highest rankings were for fluoroquinolone-resistant Salmonella enterica serotype Typhi (72%), Shigella spp (70%), and Neisseria gonorrhoeae (64%). Other important pathogens on the list include Pseudomonas aeruginosa and Staphylococcus aureus. The results of the preferences survey showed a strong inter-rater agreement, with Spearman's rank correlation coefficient and Kendall's coefficient of concordance both at 0·9. The final ranking showed high stability, with clustering of the pathogens based on experts’ backgrounds and origins not resulting in any substantial changes to the ranking.
Table 1. Criteria definitions and scoring systems
| Empty Cell | Empty Cell | Description |
|---|---|---|
| Mortality | ||
| Definition | Case-fatality ratio (%)—ie, the pooled prevalence of all-cause mortality among patients with infections caused by antibiotic-resistant bacteria | |
| Scoring system | ||
| High | >30% | |
| Medium-high | 21–30% | |
| Medium | 11–20% | |
| Medium-low | 5–10% | |
| Low | <5% | |
| Incidence | ||
| Definition | Global incidence of cases of infection caused by antibiotic-resistant bacteria per million population (all ages, all sexes) | |
| Scoring system | ||
| High | >10 000 cases per million population | |
| Medium-High | 5001–10 000 cases per million population | |
| Medium | 1001–5000 cases per million population | |
| Medium-Low | 100–1000 cases per million population | |
| Low | <100 cases per million population | |
| Non-fatal health burden | ||
| Definition | YLDs per million population, including all ages and all sexes, attributable to infections by antibiotic-resistant bacteria | |
| Scoring system | ||
| High | >1·5 YLDs per million population | |
| Medium-High | 1·1–1·5 YLDs per million population | |
| Medium | 0·51–1 YLDs per million population | |
| Medium-Low | 0·11–0·5 YLDs per million population | |
| Low | ≤0·1 YLDs per million population | |
| Trends in resistance | ||
| Definition | 10-year trend in resistance rate, defined as the percentage of antibiotic-resistant bacteria out of the total number of isolates tested | |
| Scoring system | ||
| Level 5 | Increasing trend in three or more WHO regions (or in most regions with data) | |
| Level 4 | Increasing trend in two WHO regions | |
| Level 3 | Increasing trend in one WHO region | |
| Level 2 | Stable trend in all WHO regions | |
| Level 1 | Significantly decreasing trend in at least one WHO region, with no increase in the others | |
| Transmissibility | ||
| Definition | Evidence of transmission of the antibiotic-resistant bacteria among different pathways in two distinct domains: (1) outbreak capability (human-to-human transmission in health-care or community settings); and (2) transmission potential between humans and animal, food, and environmental compartments | |
| Scoring system | ||
| High | Well documented outbreak capability and high transmission potential (defined as the capability of spreading between humans and across other One Health compartments) | |
| Medium-high | Well documented outbreak capability and moderate transmission potential; or moderately documented outbreak capability and high transmission potential | |
| Medium | Poorly documented outbreak capability and high transmission potential;well documented outbreak capability and low transmission potential; or moderately documented outbreak capability and moderate transmission potential | |
| Medium-low | Moderately documented outbreak capability and low transmission potential; or poorly documented outbreak capability and moderate transmission potential | |
| Low | Poorly documented outbreak capability and low transmission potential | |
| Preventability | ||
| Definition | The existence and effectiveness of preventive measures in containing the transmission of the antibiotic-resistant bacteria and reducing disease burden according to two distinct aspects of preventability: (1) individual-based infection prevention and control measures (including hand hygiene and standard and transmission-based precautions); and (2) community-based infection prevention and control measures (including vaccination, water, sanitation, and hygiene, access to health services, and food safety) | |
| Scoring system | ||
| High | >5 points | |
| Medium-high | 5 points | |
| Medium | 4 points | |
| Medium-low | 3 points | |
| Low | <3 points | |
| Scoring criteria | ||
| Infection prevention and control measures | Effective and sufficient (2 points); recommended, existing, and effective (1 point); or not universally recommended due to low efficacy or feasibility (0 points) | |
| Decolonisation or chemoprophylaxis | Existing and effective (2 points); existing and partly effective or restricted to patients at high risk (1 point); or not existing or ineffective (0 points) | |
| Public health interventions in the community | Existing and effective, or not needed (2 points); existing and partly effective (1 point); or not existing or ineffective (0 points) | |
| Treatability | ||
| Definition | Composite criterion encompassing number of molecules listed in the guidelines, their efficacy ranking (first or lower lines of treatment vs last resort), safety profile, availability of oral or OPAT formulation, presence of paediatric formulation, concomitant resistance, and cost | |
| Scoring system | ||
| High | >12 points | |
| Medium-high | 10–11 points | |
| Medium | 8–9 points | |
| Medium-low | 6–7 points | |
| Low | ≤5 points | |
| Scoring criteria | ||
| Number of first-line options recommended by evidence-based guidelines | One antibiotic class (2 points); or two or more antibiotic classes (2 points per option) | |
| Concomitant resistance reported for first-line option | >20% (−1 point per option); or ≤20% (0 points) | |
| Availability of alternative options for the most typical infectious syndrome | No option available, or options available but with a poor toxicity profile, or option available but recommended only in combination (−1 point); options available with a fair toxicity profile, recommended in monotherapy, but with co-resistance >20% (0 points); or at least one alternative available with a fair toxicity profile, recommended also in monotherapy, and with co-resistance ≤20% (1 point) | |
| Formulations | Availability of oral options (1 point); availability of OPAT option (1 point); or available options approved or tested for paediatric population (1 point) | |
| Accessibility | High cost (−1 point); or low cost (0 points) | |
| Antibacterial pipeline | ||
| Definition | Extent to which the antibacterial pipeline, both currently and over the next 5–7 years, can effectively meet the clinical needs for treating each antibiotic-resistant bacterium; the criterion considers the number of newly approved antibiotics in the last 5–7 years, as well as the number of candidates in the clinical developmental pipeline that meet WHO innovation criteria (such as new chemical classes, novel targets, and absence of cross-resistance), and it also evaluates the availability of oral formulations for both the new candidates and those under development | |
| Scoring system* | ||
| Unlikely | The pathogen has few or no potential active candidates in phase 1–3 according to WHO clinical pipeline analyses from July, 2017 to Nov, 2021; the pathogen has few or no candidates with ongoing MAAs or NDAs; or the pathogen had very few or no newly approved antibiotics between July, 2017 and Dec, 2022 | |
| Possible | The pathogen has one or more potential active candidates in phase 1–3 according to WHO clinical pipeline analyses from July, 2017 to Nov, 2021; the pathogen has one or more candidates with ongoing MAAs or NDAs; or the pathogen had one or more newly approved antibiotics between July, 2017 and Dec, 2022 | |
| Likely | The pathogen has a robust pipeline with multiple potential active candidates in phase 1–3 according to WHO clinical pipeline analyses from July, 2017 to Nov, 2021; or the pathogen has multiple candidates with ongoing MAAs or NDAs | |
*Points were assigned according to a scoring system based on number of newly approved antibiotics (2017–22), number and novelty of pipeline candidates (based on WHO innovation criteria), and availability of oral formulations; point totals were used to assign pathogens to the categories of unlikely, possible, or likely based on predefined thresholds, as described in the WHO BPPL report.15
Table 2. Comparative overview of bacterial pathogen priority tiers, 2017 versus 2024
| Empty Cell | 2017 | 2024 |
|---|---|---|
| Critical priority | Acinetobacter baumannii, carbapenem-resistant; Pseudomonas aeruginosa, carbapenem-resistant; Enterobacteriaceae, carbapenem-resistant, third-generation cephalosporin-resistant | A baumannii, carbapenem-resistant; Enterobacterales, third-generation cephalosporin-resistant; Enterobacterales, carbapenem-resistant; Mycobacterium tuberculosis, rifampicin-resistant* |
| High priority | Enterococcus faecium, vancomycin-resistant; Staphylococcus aureus, meticillin-resistant, vancomycin intermediate and-resistant; Helicobacter pylori, clarithromycin-resistant; Campylobacter spp, fluoroquinolone-resistant; salmonellae, fluoroquinolone-resistant; Neisseria gonorrhoeae, cephalosporin-resistant, fluoroquinolone-resistant | Salmonella enterica serotype Typhi, fluoroquinolone-resistant; Shigella spp, fluoroquinolone-resistant; E faecium, vancomycin-resistant; P aeruginosa, carbapenem-resistant; non-typhoidal Salmonella, fluoroquinolone-resistant; N gonorrhoeae, third-generation cephalosporin-resistant, fluoroquinolone-resistant; S aureus, meticillin-resistant |
| Medium priority | Streptococcus pneumoniae, penicillin non-susceptible; Haemophilus influenzae, ampicillin-resistant; Shigella spp, fluoroquinolone-resistant | Group A streptococci, macrolide-resistant; S pneumoniae, macrolide-resistant; H influenzae, ampicillin-resistant; group B streptococci, penicillin-resistant |
Pathogens are streamlined by family or order and categorised into three priority tiers.*
Rifampicin-resistant M tuberculosis was included after an independent analysis with parallel criteria and subsequent application of the multicriteria decision analysis matrix.
Interpretation
The 2024 WHO BPPL is a key tool for prioritising research and development investments and informing global public health policies to combat AMR. Gram-negative bacteria and rifampicin-resistant M tuberculosis remain critical priority pathogens, underscoring their persistent threat and the limitations of the current antibacterial pipeline. Focused efforts and sustained investments in novel antibacterials are needed to address AMR priority pathogens, which include high-burden antibiotic-resistant bacteria such as Salmonellaand Shigella spp, N gonorrhoeae, and S aureus. Beyond research and development, efforts to address these pathogens should also include expanding equitable access to existing drugs, enhancing vaccine coverage, and strengthening infection prevention and control measures.
Funding
This work is based on the development of the 2024 WHO BPPL, which was conducted by the WHO AMR Division through grants from the Government of Austria, the Government of Germany, the Government of Saudi Arabia, and the European Commission's Health Emergency Preparedness and Response Authority.
