Bacterial Priority Pathogens List (BPPL)

The Bacterial Priority Pathogens List (BPPL) is a strategic classification developed by the World Health Organization (WHO) to identify and rank bacterial pathogens that pose the greatest threat to global health due to their resistance to antibiotics. The BPPL serves as a global framework for guiding research and development (R&D) of new antibiotics, strengthening antimicrobial resistance (AMR) surveillance, and informing public health policies.

Background and Purpose

Antimicrobial resistance has emerged as one of the most pressing challenges in modern medicine. The misuse and overuse of antibiotics have led to the evolution of resistant bacterial strains, rendering many treatments ineffective. To address this, WHO first released the Global Priority Pathogens List (PPL) in 2017, identifying antibiotic-resistant bacteria that required urgent attention.
In 2024, WHO updated and renamed this list as the Bacterial Priority Pathogens List (BPPL) to reflect new data, include additional pathogens, and broaden its focus beyond drug development to public health action. The BPPL now guides international and national efforts to target resources, research, and interventions toward the most critical bacterial threats.

Methodology and Criteria

The BPPL was developed using a multi-criteria decision analysis (MCDA) approach, assessing bacteria based on multiple factors to determine their global priority. These factors include:

• Mortality and morbidity burden caused by the pathogen
• Prevalence of resistance and trends over time
• Transmissibility and outbreak potential
• Availability and effectiveness of current treatments
• Preventability through vaccines or infection control
• Economic and societal impact
• R&D pipeline gaps for new antibiotics

Based on these factors, pathogens were grouped into three levels of priority: Critical, High, and Medium.

Structure of the BPPL

The 2024 update of the BPPL includes 24 bacterial pathogen–antibiotic resistance combinations, grouped under 15 bacterial families. The goal is to ensure that public health initiatives and research funding focus on these specific, evidence-based priorities.

Critical Priority Pathogens

The Critical Priority group includes bacteria that present the most immediate and severe threat to human health. They are often resistant to last-line antibiotics and cause serious hospital- and community-acquired infections.

• Carbapenem-resistant Acinetobacter baumannii
• Carbapenem-resistant Enterobacterales
• Third-generation cephalosporin-resistant Enterobacterales
• Rifampicin-resistant Mycobacterium tuberculosis

These bacteria are associated with high mortality rates, limited treatment options, and the potential for widespread transmission in healthcare settings.

High Priority Pathogens

The High Priority category includes bacterial species that cause significant disease burdens globally and show increasing resistance to key antibiotics. These pathogens are of major concern in both community and hospital environments.

• Salmonella Typhi (fluoroquinolone-resistant)
• Shigella species (fluoroquinolone-resistant)
• Neisseria gonorrhoeae (cephalosporin- and fluoroquinolone-resistant)
• Staphylococcus aureus (methicillin-resistant, MRSA)
• Enterococcus faecium (vancomycin-resistant, VRE)

These bacteria contribute to both endemic and epidemic infections and have become increasingly difficult to treat due to resistance to commonly used antibiotics.

Medium Priority Pathogens

The Medium Priority group includes bacteria that are still largely treatable but show rising resistance in certain regions or populations. Continued monitoring and preventive strategies are essential to prevent them from becoming high-priority threats.

• Streptococcus pneumoniae (macrolide-resistant)
• Group A Streptococcus (macrolide-resistant)
• Group B Streptococcus (penicillin-resistant)
• Haemophilus influenzae (ampicillin-resistant)

These bacteria are significant causes of respiratory tract infections, meningitis, and neonatal infections, and their increasing resistance poses a concern for community health.

Significance of the BPPL

The BPPL plays a central role in global AMR policy and health system strengthening. It serves to:

• Guide research and innovation by identifying pathogens with the greatest unmet medical need.
• Inform national health strategies for antibiotic use, surveillance, and infection control.
• Support development of new antibiotics, vaccines, and diagnostics.
• Encourage global collaboration among governments, academia, and the pharmaceutical industry.

By focusing attention on the bacteria most responsible for antibiotic resistance–related deaths, the BPPL aligns with global initiatives to reduce AMR as part of the One Health approach, integrating human, animal, and environmental health.

Implementation and Adaptation

Countries are encouraged to adapt the BPPL to their own epidemiological contexts, creating national priority pathogen lists to guide local surveillance and antimicrobial stewardship programmes. For instance, high-burden countries may emphasise pathogens like Klebsiella pneumoniae or Salmonella Typhi, while others may focus on hospital-acquired pathogens such as Pseudomonas aeruginosa.
Healthcare facilities use these data to design institutional antibiograms, adjust empirical treatment protocols, and strengthen infection prevention and control (IPC) measures.

Limitations and Challenges

While the BPPL provides a global framework, its implementation faces several challenges:

• Data gaps in low- and middle-income countries limit accurate resistance assessment.
• Rapid evolution of resistance necessitates frequent updates to the list.
• Limited research funding and slow antibiotic development hinder timely responses.
• Variation in regional epidemiology means that global priorities may not always reflect local realities.

Nonetheless, the BPPL remains an essential guide for focusing attention and resources where they are most needed.

Broader Implications for Global Health

The Bacterial Priority Pathogens List highlights the urgency of addressing antimicrobial resistance as a global health security threat. It underscores the need for:

• Enhanced surveillance systems to track resistance trends.
• Rational antibiotic use through stewardship programmes.
• Investment in vaccine development to prevent bacterial infections.
• Promotion of public awareness about responsible antimicrobial use.

It also complements other WHO initiatives, such as the Global Antimicrobial Resistance and Use Surveillance System (GLASS) and the Global Action Plan on Antimicrobial Resistance, which aim to coordinate and strengthen international responses to AMR.