The World Health Organization (WHO) has released the 2024 update of its Bacterial Priority Pathogens List (BPPL). This list categorises 15 families of antibiotic-resistant bacteria into critical, high, and medium priority groups, aiming to guide the development of new treatments to curb antimicrobial resistance (AMR).
The Centres for Disease Control and Prevention states that AMR occurs when bacteria, viruses, fungi, and parasites no longer respond to medicines, increasing the severity of illnesses and the risk of disease spread and mortality. This resistance is largely fueled by the misuse and overuse of antimicrobials.
Updated Bacterial Priority Pathogens List
The updated BPPL is based on new evidence and expert insights, intended to direct research and development (R&D) towards new antibiotics and enhance international collaboration to spur innovation.
By mapping the global burden of drug-resistant bacteria and their public health impact, this list is essential for guiding investment and addressing the antibiotics pipeline and access crisis, said WHO. The organisation informed that since the initial release of the BPPL in 2017, the threat of AMR has escalated, diminishing the effectiveness of many antibiotics and jeopardising the advances of modern medicine.
The Challenge Of Antibiotic Resistance
Dr Yukiko Nakatani, WHO's Assistant Director-General, Antimicrobial Resistance ad interim, highlighted the global threats posed by critical priority pathogens. These include gram-negative bacteria resistant to last-resort antibiotics and Mycobacterium tuberculosis resistant to rifampicin. These bacteria have a high burden, resist treatment, and can transfer resistance to other bacteria. Gram-negative bacteria, in particular, have inherent capabilities to develop new resistance mechanisms and share genetic material, facilitating drug resistance in other bacteria.
High-priority pathogens such as Salmonella, Shigella, Pseudomonas aeruginosa, and Staphylococcus aureus pose significant challenges, especially in low- and middle-income countries and healthcare settings. Additionally, antibiotic-resistant Neisseria gonorrhoeae and Enterococcus faecium require targeted research and public health interventions due to their unique challenges, including persistent infections and resistance to multiple antibiotics.
Medium-priority pathogens, including Group A and B Streptococci (both newly added to the 2024 list), Streptococcus pneumoniae, and Haemophilus influenzae, present a high disease burden and require increased attention, especially in vulnerable populations like children and the elderly, particularly in resource-limited settings.
Dr Jérôme Salomon, WHO's Assistant Director-General, Universal Health Coverage, Communicable and Noncommunicable Diseases, emphasised that AMR threatens our ability to effectively treat high-burden infections such as tuberculosis, leading to severe illness and increased mortality rates. The BPPL 2024 underscores the need for a comprehensive public health approach to AMR, including universal access to quality and affordable measures for prevention, diagnosis, and appropriate treatment of infections. This approach is outlined in WHO's People-centred approach to addressing AMR and the core package of AMR interventions, crucial for mitigating AMR's impact on public health and the economy.
Changes From The 2017 List
The 2024 BPPL saw the removal of five pathogen-antibiotic combinations and the addition of four new ones. The listing of third-generation cephalosporin-resistant Enterobacterales as a standalone item in the critical priority category highlights their significant burden and need for targeted interventions, particularly in low- and middle-income countries. The transition of carbapenem-resistant Pseudomonas aeruginosa (CRPA) from critical to high priority reflects recent reports of decreased global resistance. Nonetheless, continued investment in R&D and other prevention and control strategies for CRPA remains vital due to its significant burden in certain regions.
The WHO BPPL 2024 includes the following bacteria:
Critical Priority
- Acinetobacter baumannii, carbapenem-resistant: Bloodstream infections, pneumonia (especially ventilator-associated pneumonia), urinary tract infections, wound infections, and meningitis.
- Enterobacterales, third-generation cephalosporin-resistant: Causes urinary tract infections, bloodstream infections, pneumonia, and intra-abdominal infections.
- Enterobacterales, carbapenem-resistant: Causes urinary tract infections, bloodstream infections, pneumonia, and intra-abdominal infections.
- Mycobacterium tuberculosis, rifampicin-resistant: Causes Tuberculosis
High Priority
- Salmonella Typhi, fluoroquinolone-resistant: Causes typhoid fever
- Shigella spp, fluoroquinolone-resistant: Causes shigellosis, also known as bacillary dysentery, which leads to diarrhoea (often bloody), fever, and stomach cramps.
- Enterococcus faecium, vancomycin-resistant: Causes bloodstream infections, urinary tract infections, wound infections, and endocarditis (infection of the heart valves).
- Pseudomonas aeruginosa, carbapenem-resistant: Causes pneumonia (especially ventilator-associated pneumonia), bloodstream infections, urinary tract infections, surgical wound infections, and infections in burn patients.
- Non-typhoidal Salmonella, fluoroquinolone-resistant: Causes gastroenteritis, characterised by diarrhoea, abdominal cramps, fever, nausea, and vomiting. In some cases, it can cause severe systemic infections such as septicemia (blood poisoning).
- Neisseria gonorrhoeae, third-generation cephalosporin- and/or fluoroquinolone-resistant: Causes gonorrhoea, a sexually transmitted infection
- Staphylococcus aureus, methicillin-resistant: Causes skin and soft tissue infections (such as abscesses and cellulitis), pneumonia, bloodstream infections (sepsis), and surgical site infections.
Medium Priority
- Group A streptococci, macrolide-resistant: Causes strep throat (pharyngitis), scarlet fever, impetigo (a skin infection), cellulitis, and invasive diseases such as streptococcal toxic shock syndrome and necrotising fasciitis.
- Streptococcus pneumoniae, macrolide-resistant: Causes bacterial pneumonia, meningitis, otitis media (middle ear infections), and sinusitis. It can also cause bacteremia (bacterial infection of the blood).
- Haemophilus influenzae, ampicillin-resistant: Causes respiratory tract infections such as pneumonia and bronchitis, meningitis, otitis media, and sinusitis.
- Group B streptococci, penicillin-resistant: Major cause of neonatal infections, including sepsis, pneumonia, and meningitis.
The changes since 2017 highlight the dynamic nature of AMR, necessitating tailored interventions. Adapting the BPPL to country and regional contexts can better account for variations in pathogen distribution and AMR burden. For instance, antibiotic-resistant Mycoplasma genitalium, not included in the list, is an emerging concern in some regions.